abdominal pain in pregnancy: diagnoses and imaging unique to

WS14 AJR:194, June 2010

AJR Integrative Imaging

LIFELONG LEARNING FOR RADIOLOGY

Abdominal Pain in Pregnancy: Diagnoses and Imaging Unique to Pregnancy—ReviewCourtney A. Woodfield1, Elizabeth Lazarus1, Karen C. Chen1,2, William W. Mayo-Smith1

Keywords: abdominal pain, CT, MRI, ultrasound, women’s imaging

DOI:10.2214/AJR.07.7139

Received November 14, 2008; accepted after revision November 4, 2009.1Department of Diagnostic Imaging, The Warren Alpert Medical School of Brown University, Women and Infants Hospital, Rhode Island Hospital, 593 Eddy St., Providence, RI 02903. Address correspondence to C. A. Woodfield ([email protected]).2Present address: Department of Radiology, University of California at San Diego, San Diego, CA.

WEB This is a Web exclusive article.

AJR 2010;194:WS14–WS30 0361–803X/10/1946–WS14 © American Roentgen Ray Society

ObjectiveAbdominal pain during pregnancy can be caused by a wide

variety of diseases including disorders of the obstetric, gyne-cologic, gastrointestinal, hepatobiliary, genitourinary, and vascular systems. Some causes are unique to pregnancy, are exacerbated by pregnancy, or require an altered imaging al-gorithm for diagnosis during pregnancy. The educational ob-jectives of this review article are for the participant to exer-cise, self-assess, and improve his or her understanding of the imaging evaluation of abdominal pain during pregnancy.

ConclusionThis article reviews the causes of abdominal pain that

are unique to pregnancy as well as some of the more com-mon and severe causes of abdominal pain in which the im-aging workup differs in the pregnant population. The rela-tive advantages of using ultrasound, CT, and MRI to help establish the cause of the pain are also reviewed.

IntroductionA wide variety of diseases, including disorders of the ob-

stetric, gynecologic, gastrointestinal, hepatobiliary, genito-urinary, and vascular systems, can present as abdominal pain during pregnancy [1–3] (Table 1). The clinical diagno-sis of an intraabdominal disease in pregnant women is often obscured by concurrent maternal physiologic and anatomic changes [3, 4]. Guarding in the setting of peritonitis may not occur because of the loss of elasticity in the abdominal wall musculature [2]. Leukocytosis in pregnancy is less use-ful in clinical evaluation because WBC count is typically elevated in pregnancy, ranging from 6,000–16,000 cells/μL during the first and second trimesters to 20–30,000 cells/μL at the end of the third trimester [3]. Ureteral compression and displacement of intraabdominal organs, including the appendix, by the gravid uterus may also confound the clin-ical presentation [2].

A delay in the diagnosis of many of the causes of ab-dominal pain can be threatening to both the mother and the fetus [3, 5]. Imaging can clarify a confusing clinical pic-

ture and expedite diagnosis. Ultrasound is widely used as the initial diagnostic imaging technique during pregnancy because of its availability, portability, and lack of ionizing radiation. Ultrasound often can elucidate the cause of ab-dominal pain, particularly if pain is due to an obstetric and gynecologic abnormality. However, evaluation of the bowel, pancreas, ureters, and mesenteric vasculature may be lim-ited on ultrasound because of patient body habitus, a small field of view, and the presence of overlying structures. Air within the bowel can particularly limit evaluation of the mesenteric vessels, pancreas, and bowel.

MRI is also a useful technique for imaging pregnant patients given the lack of ionizing radiation. Several recent studies have shown that MRI is valuable in evaluating abdominal pain dur-ing pregnancy, especially in the diagnosis of appendicitis, which is the most common cause of an acute abdomen in preg-nancy [6–8]. To date, no deleterious effects to the developing fetus exposed to MRI have been reported. Therefore, no spe-cific consideration for MRI during the first, second, or third trimester has been recommended [9]. The use of MRI for the evaluation of abdominal pain during pregnancy may be de-pendent on institutional availability and radiologist experience. A recent guidance document for safe MR practices from the American College of Radiology (ACR) does not recommend the routine use of gadolinium during pregnancy [9]. Gadolini-um-based MR contrast agents are known to pass through the placenta to the fetal circulation. The contrast material is then excreted by the fetal kidneys into the amniotic fluid where the agent can remain for an indeterminate amount of time. To date, no large, well-controlled studies have been performed to document the presence or absence of adverse fetal effects re-sulting from maternal gadolinium administration. Therefore, the potential risks to the fetus remain unknown [9].

Examinations using ionizing radiation—in particular, CT—can also accurately diagnose many causes of abdomi-nal pain during pregnancy. A risk–benefit analysis is par-ticularly warranted before performing an examination in-volving ionizing radiation on a pregnant or potentially pregnant patient. However, most diagnostic imaging stud-

AJR:194, June 2010 WS15

Abdominal Pain in Pregnancy

ies utilizing ionizing radiation do not expose the fetus to a radiation dose high enough to result in developmental or neurologic deficits. Therefore, ionizing radiation examina-tions can still be offered to pregnant women when the study is in the best health interest of the mother and the patient understands the minimal and unknown risks to the fetus [10]. For example, CT remains the most reliable technique for depicting obstructing urinary tract calculi in pregnant women [11]. Based on our experience with a low-dose renal calculus protocol (160 mA and 140 kVp on a 16-MDCT scanner), the mean radiation dose delivered to the female pelvis is 16 mGy and to the fetus, 4–7.2 mGy and 8.5–11.7 mGy at 0 and 3 months of gestation, respectively [12]. This dose is below the recommended 50-mGy (5-rad) maternal

dose limit for avoiding deterministic radiation effects (i.e., effects that have a radiation threshold below which they should not occur) such as fetal teratogenesis [13]. There is no known maternal radiation limit for fetal stochastic ef-fects (i.e., effects that can occur regardless of radiation dose) such as carcinogenesis; therefore, radiation levels should be kept as low as reasonably achievable (ALARA) for all ionizing radiation studies [13].

Similar to gadolinium-based MR contrast agents, iodinat-ed IV contrast agents have been shown to cross the placenta to the fetal circulation and ultimately to be excreted into the amniotic fluid. No teratogenic fetal effects from a single in utero exposure to iodinated contrast material at diagnostic doses have been reported. However, there have also been no published large, well-controlled studies investigating poten-tial teratogenic effects from iodinated contrast agents. In early reports, investigators described transient congenital hypothyroidism after amniofetography using iodinated con-trast material [14]. However, more recent small studies of pregnant patients receiving iodinated contrast material as part of a CT protocol did not show any effect on thyroid function [15]. Similar to its recommendations with regard to gadolinium-based contrast agents, the ACR recommends IV iodinated contrast administration during pregnancy only when it is deemed necessary for prompt and accurate evalua-tion of the pregnant patient’s medical condition [16].

This review focuses on the causes of abdominal pain that are unique to pregnancy as well as some of the more com-mon and severe causes of abdominal pain in which the im-aging workup differs in the pregnant population compared with the nonpregnant population. This article also explores the relative advantages of using different imaging tech-niques including ultrasound, CT, and MRI to help establish the cause of the pain.

Obstetric CausesDuring the first trimester of pregnancy, common causes

of abdominal and pelvic pain include early pregnancy fail-ure and ectopic pregnancy. During the second and third tri-mesters, causes of pain include preterm labor and the less common, but more severe, complications of placental abruption and uterine rupture.

Early Pregnancy FailureSpontaneous abortion occurs in approximately 10–12%

of known first trimester pregnancies. Although the patient may be asymptomatic, spontaneous abortion commonly re-sults in pain and vaginal bleeding [17].

Ultrasound is the initial diagnostic test of choice for a first trimester patient with pain and bleeding. Ultrasound can confirm early pregnancy failure with high specificity if no fetal cardiac activity is detected by the time the embryo measures 5 mm in length or if the pregnancy is known to be 6.5 weeks without an embryo with a heartbeat [18].

TABLE 1: Causes of Abdominal Pain in Pregnant Women by Organ System

Organ System Cause

Obstetric Abortion

Ectopic pregnancy

Preterm labor

Placental abruption

Uterine rupture

Gynecologic Adnexal mass or ovarian cyst

Adnexal torsion

Uterine leiomyoma

Endometriosis

Pelvic inflammatory disease

Gastrointestinal Appendicitis

Inflammatory bowel disease

Intestinal obstruction

Gastroesophageal reflux

Peptic ulcer disease

Hepatobiliary HELLP syndrome

Acute fatty liver of pregnancy

Cholelithiasis or choledocholithiasis

Acute cholecystitis

Acute pancreatitis

Hepatitis

Genitourinary Hydronephrosis of pregnancy

Urolithiasis

Pyelonephritis

Cystitis

Vascular Gonadal vein thrombosis

Mesenteric vein thrombosis

Gonadal vein syndrome

Aneurysm rupture

Vasculitis

Note—HELLP = hemolysis, elevated liver enzymes, low platelet count.

Woodfield et al.

WS16 AJR:194, June 2010

Additional sonographic findings such as abnormal gesta-tional sac size or shape and embryonic bradycardia may be suggestive of a poor outcome but are not definitive for early pregnancy failure. Large gestational sacs without a yolk sac or an embryo are worrisome. The most widely accepted “dis-criminatory” sizes of the gestational sac using endovaginal ultrasound are an 8-mm mean sac diameter by which a yolk sac must be visualized and a 16-mm mean sac diameter by which an embryo must be visualized for the pregnancy to be considered normal [19, 20]. However, a range of higher dis-criminatory values has been reported in the literature, with mean sac diameter values up to 13 mm for visualization of the yolk sac and 18 mm for visualization of the embryo proposed before considering a pregnancy abnormal [19–21]. Given this range of values, use of the discriminatory sac size is limited. Worrisome findings on ultrasound also include slow embry-onic cardiac activity, irregular gestational sac, and low posi-tion of the gestational sac [22]. Embryonic heartbeat rates below 80 beats per minute (bpm) at 6.0–6.2 weeks or below 100 bpm at 6.3–7.0 weeks’ menstrual age are associated with a very high rate of early pregnancy failure [23].

When the ultrasound examination either shows worri-some features or is inconclusive, such as in cases with an embryo smaller than 5 mm without a heartbeat, follow-up ultrasound is indicated. Follow-up ultrasound is typically performed 5–7 days later to allow measurable growth. Cor-relating sonographic findings with maternal serum level of β-HCG can also help indicate whether early pregnancy fail-ure has occurred. A gestational sac is expected to be visible when the β-HCG level is above 2,000 mIU/mL (third inter-

national reference preparation) and the embryo when the β-HCG level is above 10,800 mIU/mL [24].

Ectopic PregnancyEctopic pregnancy, which remains the most frequent ob-

stetric cause of death in pregnancy, often presents with ab-dominal or pelvic pain in the first trimester [25]. The inci-dence of ectopic pregnancy has been increasing steadily since 1970. This increased incidence correlates with an in-crease in the prevalence of risk factors for ectopic pregnan-cy including sexually transmitted diseases and assisted re-productive techniques [26, 27]. Ultrasound plays an instrumental role in ruling out an ectopic pregnancy if it

Fig. 1—Tubal ectopic pregnancy in woman 8 weeks’ pregnant who presented with right-sided pelvic pain. Gray-scale transvaginal ultrasound image reveals extrauterine gestational sac (arrows) with yolk sac (arrowhead) between right ovary (O) and uterus (UT).

A

Fig. 2—Interstitial ectopic pregnancy. A, Woman 7 weeks’ pregnant who presented with abdominal pain. Gray-scale transvaginal ultrasound image shows eccentric intrauterine gestational sac (arrows) containing yolk sac and embryo. Endometrium (arrowheads) extends up to, but does not surround, gestational sac; these findings are consistent with interstitial pregnancy. B, Woman 8 weeks’ pregnant who presented with abdominal pain. Coronal T2-weighted single-shot fast spin-echo MR image also shows eccentric intrauterine gestational sac (arrows) that is not surrounded by endometrium (arrowheads).

B

AJR:194, June 2010 WS17


can confirm an intrauterine pregnancy. Heterotopic preg-nancy, a coexistent ectopic and intrauterine pregnancy, is rare (1 in 7,000) in the general population. However, the incidence of heterotopic pregnancy is higher after in vitro fertilization, approaching 1% in some studies [28, 29].

In a small percentage of cases, ultrasound may conclusive-ly diagnose ectopic pregnancy if it shows an extrauterine gestational sac with a yolk sac or embryo (Fig. 1). More com-monly, ultrasound reveals findings that are only suggestive of an ectopic pregnancy—notably, an adnexal mass and pelvic free fluid. An adnexal mass is the most common sonographic finding in ectopic pregnancy, occurring in 65–84% of cases [30–32]. The adnexal mass can have a variety of appearanc-es, including appearing to be a saclike ring, solid, or complex. A small amount of pelvic free fluid can be seen in normal pregnancies, but a moderate to large amount of pelvic fluid, particularly if in association with an adnexal mass, signifi-cantly increases the risk for ectopic pregnancies. The pres-ence of fluid-containing echoes, correlating with hemoperito-neum, carries a 93% positive predictive value for ectopic pregnancy [33]. Occasionally ultrasound findings may ap-pear normal in the setting of ectopic pregnancy.

MRI can be used as a problem-solving technique for the less common nontubal forms of ectopic pregnancies when sonography is indeterminate. With its multiplanar capabili-ties, MRI can help to confirm a suspected cervical ectopic pregnancy or cesarean section scar ectopic pregnancy before treatment. In addition, MRI can help differentiate between eccentric implantation in the endometrium versus an inter-stitial ectopic pregnancy (Fig. 2). An interstitial ectopic preg-nancy on MRI will appear as a gestational sac centered in the cornual aspect of the uterine wall and will be separated from the endometrium by an intact junctional zone [34] (Fig. 2).

Placental AbruptionSymptoms of placental abruption are variable but often

include vaginal bleeding and abdominal or pelvic pain. Pla-cental abruption is defined as in utero separation of the pla-centa from the myometrium and accounts for 10–25% of prenatal deaths [35]. In most cases, ultrasound does not show any signs of abruption because the hemorrhage resulting from placental separation can pass through the cervical os. Sonographic findings suggestive of placental abruption, when they are visible, are usually due to hematomas. Visual-ization of a hematoma is clinically important because these pregnancies have a worse prognosis [35]. The most common location of hematomas in this setting is subchorionic (i.e., between the uterine wall and chorionic membrane) [36]. Ret-roplacental (behind the placenta) and preplacental (in front of the placenta) hematomas are less common. The sono-graphic appearance of a hematoma varies with its acuity. Acute hematomas are hyperechoic to isoechoic (Fig. 3). Ini-tially, the only finding of an acute or subacute hematoma on ultrasound may be an abnormally thickened placenta. In

these cases, T1-weighted MRI may be used to help distin-guish high-signal hematomas from the lower-T1-signal-in-tensity placenta [37]. Hematomas more than 1–2 weeks in age appear progressively more hypoechoic [36].

Preterm LaborPreterm labor is defined as uterine contractions strong

enough to cause cervical dilatation and effacement between 20 and 37 weeks’ gestation. The abdominal pain that ac-companies these contractions is often clinically distinguish-able, so imaging is typically not indicated for diagnosis. However, ultrasound evaluation of cervical length is the most sensitive predictor of preterm birth. The shorter the cervical length measures, the higher the risk of preterm birth. Also, the earlier a shortened cervical length is found, the higher the risk of preterm birth. A normal cervical length is more than 30 mm between 14 and 30 gestational weeks [38–40]. Cervical funneling is also associated with an increased risk of preterm labor. Funneling occurs when the internal os is open proximally and gradually narrows, ap-proximating the appearance of a cone. If funneling is pres-ent, the cervical length is almost always shortened. How-ever, the presence of funneling in a patient with a normal cervical length does not increase the risk of preterm birth.

Uterine RuptureUterine rupture is a rare, catastrophic event that often

presents with severe abdominal pain. Predisposing factors include previous uterine surgery, including cesarean deliver-ies and myomectomy, and congenital uterine malforma-tions. Uterine rupture can occur during labor or before de-livery such as in cases of interstitial ectopic pregnancies that rupture [41]. Only a very short time interval for suc-cessful intervention exists once uterine rupture has oc-curred, so imaging in this setting may consume valuable

Fig. 3—Placental abruption in woman 20 weeks’ pregnant who presented with abdominal pain and vaginal bleeding. Gray-scale transabdominal ultrasound image shows isoechoic collection in retroplacental location (arrows), representing acute retroplacental hematoma secondary to placental abruption. Normal placenta (arrowheads) is seen.

Woodfield et al.

WS18 AJR:194, June 2010

time. If imaging is performed, ultrasound, CT, or MRI may show herniation of the gestational sac contents (Fig. 4). The choice of imaging technique will depend on patient sta-bility and technique availability at a given institution.

Gynecologic CausesCommon gynecologic causes of pain during pregnancy

include complications related to adnexal masses, ovarian torsion, and leiomyomas. Adnexal masses are often first de-tected at the time of a routine first trimester dating or sec-ond trimester anatomic survey ultrasound examination [2]. Ovarian torsion and leiomyoma degeneration both have a higher incidence during pregnancy [42–44].

Adnexal MassesAdnexal masses occur in approximately 2% of all pregnan-

cies [3]. Adnexal masses are not a usual cause of pain, with 65% of these masses being asymptomatic and discovered inci-dentally on physical examination or sonography [2]. The size of the mass also does not necessarily dictate whether it will cause pain [2, 3]. However, if an adnexal mass is compressed, if it compresses an adjacent organ or organs, as is more likely to occur during pregnancy in association with an enlarging gravid uterus, or if it becomes complicated by torsion, hemor-rhage, or rupture, the adnexal mass may present with pain. Imaging evaluation of the adnexa should be performed, start-ing with ultrasound, in all pregnant women presenting with pain [42, 45]. Ultrasound provides the ability to distinguish adnexal masses that are small, uncomplicated, and likely to spontaneously resolve from those that appear larger and more complex with a higher likelihood of malignancy, torsion, or persistent pain from mass effect during pregnancy.

The most common adnexal masses during pregnancy are corpus luteum or other functional ovarian cysts. The dif-ferential diagnosis for a complex-appearing adnexal mass

includes hemorrhagic corpus luteum cyst, ovarian cystade-noma, and ovarian teratoma. However, approximately 1–8% of adnexal masses found during pregnancy are ma-lignant [42]. Therefore, when the sonographic appearance of an adnexal mass is not specific, MRI can be used for fur-ther characterization to help determine patient manage-ment during pregnancy [45, 46] (Fig. 5). Complex adnexal masses, particularly if they are already a source of pain, may warrant surgical removal during pregnancy because of an increased risk of torsion, rupture, and malignancy [47].

Ovarian TorsionThe incidence of ovarian torsion is increased during preg-

nancy, complicating 1 in 800 pregnancies. This increased in-cidence is most likely related to an increased incidence of adnexal masses. Up to 7% of adnexal masses reportedly re-sult in ovarian torsion during pregnancy [42, 43]. However, torsion can also occur in an otherwise normal ovary, usually the right ovary [2, 3]. During pregnancy, ovarian torsion most commonly occurs between 6 and 14 weeks’ gestation when uterine enlargement is most rapid [3, 45]. However, in at least one study, up to 45% of cases of ovarian torsion pre-sented during the second and third trimesters [48].

Sonography is the preferred imaging technique for the diag-nosis of ovarian torsion, with the diagnosis made by a combi-nation of gray-scale and color Doppler findings. The most con-sistent finding is an enlarged ovary [43, 49]. Additional findings include a twisted vascular pedicle, pelvic free fluid, and a coex-istent ovarian mass. The color Doppler findings are often vari-able. The most frequent finding on Doppler evaluation of the ovary is either reduced or absent arterial flow. However, ovari-an arterial waveforms may be detectible in the setting of tor-sion. This is theorized to be either due to venous thrombosis alone eliciting symptoms or due to the dual blood supply of the ovary [49, 50]. If the ultrasound findings are indetermi-

A

Fig. 4—Uterine rupture in woman 15 weeks’ pregnant who presented with severe abdominal pain. A and B, Gray-scale sagittal ultrasound images show fetus (arrow, A) superior to uterine fundus (arrowheads, A) and distension of endometrium with heterogeneous hypoechoic material (arrowheads, B) due to hemorrhage after uterine rupture. Abdominal pregnancy resulting from rupture of interstitial ectopic pregnancy was diagnosed at surgery and pathology.

B

AJR:194, June 2010 WS19


nate for torsion, MRI may better show ovarian edema result-ing from early or intermittent ovarian torsion [45] (Fig. 6).

LeiomyomasUterine leiomyomas are commonly encountered during

pregnancy, with 1 in 500 pregnant women hospitalized for a leiomyoma-related complication [44]. Approximately half of all leiomyomas grow during pregnancy, mainly in the first

trimester because of rising estrogen levels [51]. Abdominal pain and uterine contractions can result from necrosis and degeneration of leiomyomas secondary to rapid growth. “Red degeneration” is the most common type of degenera-tion during pregnancy and occurs when a leiomyoma out-grows its blood supply with resulting hemorrhage. Such leio-myomas can appear on ultrasound as circumscribed masses with cystic spaces or heterogeneous echogenicity [51, 52]

A

Fig. 6—Degenerated fibroid in woman 17 weeks’ pregnant who presented with right-sided abdominal pain. A and B, Transverse (A) and sagittal (B) transabdominal ultrasound images show exophytic fibroid (straight arrows) extending from right lateral aspect of uterus. Inner hypoechoic region with low-level echoes (arrowheads) represents cystic degeneration secondary to necrosis. Intrauterine fetal head (curved arrow, A) is seen.

B

A

Fig. 5—Ovarian torsion in woman 11 weeks’ pregnant who presented with 2 days of lower abdominal and pelvic pain. A, Transverse gray-scale transabdominal ultrasound image through pelvis shows cystic and solid midline mass (arrows). Separate normal right ovary was seen transvaginally (not shown). Separate left ovary was not seen on transabdominal or transvaginal ultrasound. MRI was performed for further evaluation 1 hour later. B, Coronal T2-weighted fast spin-echo MR shows enlarged, partially necrotic left ovary (black arrows) and cystic mass arising from left ovary (white arrow) with few septations in inferior aspect of mass (arrowhead). Left ovary and mass were surgically removed later that day. Pathology results were torsed, necrotic left ovary with mucinous cystadenocarcinoma of left ovary serving as lead point mass.

B

Woodfield et al.

WS20 AJR:194, June 2010

(Fig. 7). Ultrasound can further confirm a degenerating leio-myoma as the source of pain if the patient experiences pain when the probe is directly placed over the leiomyoma [44]. On MRI, red degeneration of a leiomyoma manifests as pe-ripheral or diffuse high signal intensity on T1-weighted im-ages and corresponding variable signal intensity with or without a low-signal-intensity rim on T2-weighted images [48]. Leiomyomas are also the most common solid adnexal masses in pregnancy [45]. Exophytic leiomyomas have the potential to torse during pregnancy, causing pain due to loss of blood supply and rapid necrosis.

Gastrointestinal CausesGastrointestinal causes of pain during pregnancy include

appendicitis and other inflammatory, infectious, and obstruc-tive processes of the bowel. These diseases are neither unique to nor more common in pregnancy but can be more difficult to diagnose during pregnancy. The approach to imaging the bowel of a pregnant patient also differs from that of a non-pregnant patient because ultrasound and MRI are typically preferred over techniques that impart ionizing radiation such as radiography and CT.

AppendicitisAppendicitis is the most common nonobstetric reason for

emergency surgery during pregnancy, occurring in approxi-

mately 1 in 1,500 deliveries [53]. Early diagnosis is important because a 66% increased incidence of appendiceal perfora-tion during pregnancy—with a resulting increased rate of fetal loss and maternal mortality—has been reported with surgical delays greater than 24 hours from the time of symp-tom onset [53]. Clinically diagnosing appendicitis during

Fig. 8—Acute appendicitis in 25-year-old pregnant woman who presented with right lower quadrant pain. Sagittal gray-scale ultrasound image shows blind-ending, dilated, tubular structure (arrows) in right lower quadrant containing ovoid echogenic structure (arrowhead) with posterior acoustic shadowing. Acute appendicitis with appendicolith was diagnosed at surgery.

A

Fig. 7—Ovarian edema in woman 13 weeks’ pregnant who presented with right lower quadrant pain. A, Transvaginal ultrasound image with spectral Doppler shows mildly enlarged right ovary (volume = 16.1 cm3) with arterial flow. B, Axial T2-weighted single-shot fast spin-echo image from MR examination performed same day as ultrasound (A) shows increased signal intensity of central ovarian stroma (black arrow) and peripheral displacement of subcentimeter physiologic ovarian follicles (white arrows); these findings are consistent with ovarian edema. Surgery confirmed right ovarian edema due to compression of right adnexal vessels between enlarging uterus and anterior pelvic wall.

B

AJR:194, June 2010 WS21


pregnancy is difficult because of multiple factors including, first, the variable appendiceal position (the appendix is grad-ually displaced upward during pregnancy); second, limited physical examination of the gravid abdomen; and, third, the nonspecificity of symptoms such as nausea, vomiting, guard-ing, and leukocytosis during pregnancy [2, 3, 54].

The primary options for imaging pregnant patients with suspected appendicitis are ultrasound, MRI, and CT. Ultra-sound is usually the first imaging technique of choice because of its availability, lack of ionizing radiation, and lack of need for IV contrast material. The sonographic criteria for diag-nosing appendicitis in pregnant patients are the same as in nonpregnant patients: visualization of a dilated (> 6–7 mm in diameter), aperistaltic, noncompressible, and blind-ending tubular structure arising from the cecum. The outer diame-ters of both a normal appendix and an inflamed appendix are known to vary on ultrasound, with reported normal ap-pendix diameters ranging from 2 to 13 mm and inflamed ap-pendix diameters from 6 to 30 mm [55]. Therefore, an appen-dix with a diameter of between 6 and 7 mm without additional features of acute inflammation may be considered indeterminate for appendicitis [56]. Associated findings, such as appendiceal wall thickening (> 2 mm), appendicoliths, and surrounding hyperechoic inflamed fat, or hypoechoic fluid may also be seen sonographically (Fig. 8). However, ultra-sound of the appendix is a highly operator-dependent ex-amination that can be further limited by the pregnant body habitus. Sensitivities ranging from 50% to 100%, specifici-ties ranging from 33% to 92%, accuracies ranging from 73%

to 93%, and negative predictive values ranging from 64% to 88% have been reported for the sonographic diagnosis of ap-pendicitis in the general adult population [57–62]. In addi-tion, an elevated or retrocecal appendix may be difficult to find sonographically and a ruptured appendix may have non-specific findings on ultrasound. Therefore, a negative ultra-sound examination does not exclude the possibility of ap-pendicitis and if there remains high clinical suspicion for appendicitis (persistent right lower quadrant pain of uncer-tain cause), additional imaging should be considered [63].

When available, MRI is the next preferred examination for evaluating the appendix in pregnancy also because of its lack of ionizing radiation. Recent studies have shown that MRI can reliably diagnose acute appendicitis during preg-nancy with 100% sensitivity and 94% specificity [7, 64]. MR examinations for appendicitis in pregnancy at our in-stitution include an oral contrast preparation (300 mL of barium sulfate [Readi-CAT 2, E-Z-EM] and 300 mL of fer-umoxsil [GastroMARK, AMAG Pharmaceuticals]) started 2 hours before the examination. These agents are used be-cause they are the oral contrast preparations already avail-able in our department for other CT (barium sulfate) and MR (ferumoxsil) examinations, and this specific negative oral contrast preparation has been previously described in the literature as a means of limiting bowel susceptibility artifact and confirming appendiceal patency [7].

The MR examination then consists of the following se-quences: axial, sagittal, and coronal T2-weighted single-shot fast spin echo (SSFSE), axial T1-weighted dual gradient-echo,

A

Fig. 9—Acute appendicitis in 30-year-old pregnant woman who presented with right lower quadrant pain. Ultrasound findings were normal. A and B, Axial (A) and sagittal (B) T2-weighted single-shot fast spin-echo MR images reveal dilated (1.2 cm) appendix with high-T2-signal-intensity luminal contents (straight arrows) due to fluid and adjacent periappendiceal fat stranding and fluid (arrowheads); these findings are indicative of periappendiceal inflammation. Low-signal-intensity oral contrast material fills cecum (curved arrow, B). Acute appendicitis without perforation was diagnosed at surgery.

B

Woodfield et al.

WS22 AJR:194, June 2010

axial true fast imaging with steady-state precession (FISP), and axial STIR. The multiplanar T2-weighted SSFSE images allow imaging of the bowel in a relatively motionless state and help to confirm the location of the appendix in more than one plane. The axial T1-weighted gradient-echo images are ob-tained to help confirm appendiceal patency by showing bloom-ing artifact from air or oral contrast material in the appendix lumen from out-of-phase to in-phase imaging. The axial true FISP images also help differentiate high-signal-intensity ad-nexal vessels from the lower signal intensity of a normal ap-pendix, and the axial STIR sequence is used to highlight any periappendiceal edema or fluid associated with appendicitis.

The largest study to date of MRI for appendicitis in preg-nant patients has described the following criteria for diag-nosing acute appendicitis in this population: an appendix diameter of > 7 mm with high-T2-signal-intensity luminal contents, appendiceal wall thickening (> 2 mm), or periap-pendiceal fat stranding and fluid [7] (Fig. 9). An appendix with high-T2-signal-intensity luminal contents and a diam-eter of between 6 and 7 mm on MRI without associated wall thickening or periappendiceal inflammatory changes may be considered indeterminate for appendicitis and war-rants close clinical follow-up [7, 65].

Appendicitis can also be readily diagnosed on CT using the same criteria in pregnant patients as in nonpregnant patients [12]. CT is generally performed if MRI is unavailable or if the patient has contraindications to MRI to prevent a delay in the diagnosis and treatment of a possible appendicitis. Sensitivities ranging from 72% to 100%, specificities ranging from 83% to 99%, accuracies ranging from 78% to 98%, and

negative predictive values ranging from 64% to 99% have been reported for the CT diagnosis of appendicitis in the gen-eral adult population [58, 59, 61, 62, 66].

Infectious Diseases and Inflammatory Bowel DiseaseInfection and inflammation of the bowel are additional po-

tential causes of acute abdominal pain during pregnancy. In-flammatory bowel disease has a peak incidence in women of

Fig. 11—Hepatic rupture in 28-year-old recently postpartum woman with HELLP (hemolysis, elevated liver enzymes, low platelet count) syndrome and abdominal pain. Axial enhanced CT image reveals high-attenuation (52-HU) perihepatic material (arrows) diagnostic of hemoperitoneum, which was secondary to hepatic rupture. Note lower-attenuation (8-HU) small bilateral pleural effusions (arrowheads).

A

Fig. 10—Small-bowel obstruction in 31-year-old pregnant woman who presented with abdominal pain and distention. Patient has history of gastric bypass surgery. A, Transverse gray-scale ultrasound image of left abdomen shows dilated loop of bowel (arrows). B, Subsequent axial enhanced CT image through abdomen reveals multiple dilated loops of small bowel with air–fluid levels (arrows) and superior mesenteric vein thrombus (arrowhead). Small-bowel obstruction due to internal hernia was diagnosed at surgery. Hypercoagulability due to pregnancy was implicated as cause of superior mesenteric vein thrombus.

B

AJR:194, June 2010 WS23


reproductive age. Disease activity is largely independent of pregnancy; however, activity during pregnancy is associated with increased fetal loss rate and fetal growth retardation [3]. Ultrasound is often the first imaging study chosen for evaluat-ing localized or generalized abdominal pain during pregnancy and may reveal a thick-walled segment of bowel in the setting of active infection or inflammation [67]. However, cross-sec-tional imaging is commonly required to evaluate the entire extent of disease as well as any associated complications such as bowel obstruction, fistulas, or abscess formation.

Both MRI and CT can show the presence, extent, and complications of infectious and inflammatory bowel diseases. MR examinations without or with an oral preparation (MR enterography) using T2-weighted SSFSE images can readily depict thick-walled segments of small and large bowel and associated complications in pregnant patients and nonpreg-nant patients [65, 68]. Similar to CT, findings of Crohn’s dis-ease on MRI include segmental bowel wall thickening and small-bowel involvement. Additional findings such as bowel stenosis with prestenotic dilatation, fibrofatty proliferation, increased vascularity of the vasa recta, and mesenteric ade-nopathy may also be readily depicted on both CT and MRI

[69]. The role of MRI in evaluating ulcerative colitis is less established, but MRI can reportedly show the continuous co-lonic wall thickening and loss of haustral folds characteristic of ulcerative colitis [70].

Bowel ObstructionBowel obstruction is a third gastrointestinal emergency

that can arise during pregnancy with an incidence of 1 in 2,500 deliveries. Maternal mortality associated with bowel obstruction is as high as 6% and is most commonly second-ary to adhesions [71]. Pregnant patients more commonly present with bowel obstruction in the third trimester perhaps because of increased mass effect of the enlarging gravid uter-us on the large and small bowel with resulting bowel displace-ment [72]. Clinically diagnosing bowel obstruction in a preg-nant patient can be difficult because the gravid uterus limits physical examination and because some of the symptoms of bowel obstruction (abdominal pain, nausea, vomiting) are also common symptoms of pregnancy. However, the onset of such symptoms after the first trimester should raise the pos-sibility of other gastrointestinal abnormalities or diseases such as intestinal obstruction [2].

A

C

Fig. 12—Gallstone pancreatitis in 27-year-old pregnant woman who presented with right upper quadrant and epigastric pain. Patient had undergone laparoscopic cholecystectomy 2 years earlier. A, Coronal thick-slab MR cholangiopancreatography image illustrates mild dilatation of intrahepatic bile ducts (arrowheads) and moderate dilation of common bile duct (arrow). B and C, Axial T2-weighted single-shot fast spin-echo MR images through level of distal common bile duct (B) and pancreas (C) reveal dependent filling defect in distal common bile duct (arrowhead, B) and small amount of retroperitoneal and peripancreatic fluid (arrows, C). This fluid was believed to be secondary to gallstone-related pancreatitis because patient had elevated serum amylase (1,321 U/L) and lipase (1,015 U/L) levels. Subsequent ERCP with stone extraction resulted in resolution of patient’s abdominal pain and normalization of serum amylase and lipase levels. Common duct stone is not visible on coronal thick-slab MR cholangiopancreatography image because of volume averaging with high-signal-intensity bile.

B

Woodfield et al.

WS24 AJR:194, June 2010

Ultrasound is again often the first imaging study of choice for evaluating generalized abdominal pain in preg-nancy and may show dilated loops of bowel with fluid levels and aperistalsis with long-standing or high-grade obstruc-tion, but ultrasound does not reliably depict the point or cause of bowel obstruction. Therefore, cross-sectional im-aging with MRI or CT is again often required for further characterization (Fig. 10). Similar to imaging bowel inflam-mation or infection, MR studies for bowel obstruction can be performed with the use of multiplanar T2-weighted SSFSE imaging and may be performed with or without oral contrast preparation [73]. If MRI cannot be performed ex-peditiously or expertise in MR interpretation is not readily available, CT may be performed because the risk of delayed diagnosis and treatment of a potential bowel obstruction may pose a greater risk to the fetus than radiation exposure from a diagnostic examination.

Hepatobiliary CausesTwo hepatic complications unique to pregnancy that can

present with acute abdominal pain are HELLP (hemolysis, elevated liver enzymes, low platelet count) syndrome and acute fatty liver of pregnancy (AFLP). Although pancrea-titis is not unique to pregnancy, the approach to imaging pregnant patients with pancreatitis differs from that of the nonpregnant patient.

HELLP SyndromeHELLP syndrome is a rare but serious condition that

most commonly presents in the late third trimester or early postpartum period in association with severe preeclampsia or eclampsia. It is estimated that up to 10–28% of pre-eclampsia pregnancies are associated with some degree of HELLP syndrome [3]. Patients with HELLP syndrome variably present with hemolytic anemia, thrombocytope-nia (< 100,000/mm3), and liver function test abnormalities (elevated lactate dehydrogenase level, > 600 U/L; elevated bilirubin level, > 1.2 mg/dL; or elevated aspartate amino-transferase level, > 70 U/L) [2]. The deposition of intravas-cular fibrin deposits in the liver with HELLP syndrome re-sults in various hepatic manifestations ranging from hepatic congestion and edema to hepatic necrosis, hemor-rhage, and rupture, which can require emergent cesarean delivery, exploratory laparotomy, or hepatic embolization [74]. The clinical presentation of HELLP syndrome is vari-able and nonspecific. Patients most commonly present with abdominal pain and nausea. Patients with severe complica-tions of hepatic rupture and hemorrhage may present with abdominal pain that radiates to the right upper quadrant or right shoulder and with hypovolemic shock [3].

The main role of imaging in patients with clinically diag-nosed HELLP syndrome is to identify the hepatic compli-cations. Ultrasound, CT, or MRI can be used to assess the presence and extent of hepatic injury. The selected imaging

technique will depend on availability, patient stability, and whether the patient is postpartum. Ultrasound can show intra- and extrahepatic hematomas and fluid collections. CT and MR examinations can further reveal the extent of hepatic damage and can help distinguish among hepatic edema, necrosis, and hemorrhage [74] (Fig. 11).

Acute Fatty Liver of Pregnancy AFLP is also a rare but serious hepatic complication unique

to pregnancy that can be fatal. It is characterized by micro-vascular fatty infiltration of the liver and can result in both hepatic and renal failure. Patients also typically present in the late third trimester or early postpartum period with symp-toms of abdominal pain, vomiting, and jaundice. Similar to HELLP syndrome, management of AFLP centers on prompt delivery and supportive care [3]. AFLP can be difficult to dif-ferentiate from HELLP syndrome and preeclampsia or ec-lampsia clinically. However, histologically HELLP syndrome and AFLP can be readily differentiated because HELLP syn-drome is characterized by periportal hemorrhage, sinusoidal fibrin deposition, and occasional periportal necrosis, whereas AFLP is characterized by microvesicular fatty infiltration with occasional necrosis and inflammation [2].

Imaging with ultrasound, CT, or MRI may also help distin-guish between HELLP syndrome and AFLP as well as depict the extent of hepatic complications. However, in the early stages of AFLP the liver may appear normal [75]. The imag-ing of patients with suspected AFLP will depend on technique availability, patient stability, and pregnancy status. Ultra-sound is often the first technique of choice for pregnant and unstable patients and can reveal diffuse increased heterogene-ity and echogenicity of the hepatic echotexture. If the patient is postpartum, CT is often the first imaging study of choice and may reveal diffuse decreased hepatic attenuation. The role of MRI for diagnosing AFLP has not been determined, but MR examinations performed with T1-weighted dual gra-dient-echo in-phase and out-of-phase sequences can readily depict hepatic steatosis by showing loss of hepatic signal in-tensity from in-phase to out-of-phase images.

PancreatitisPancreatitis is a rare cause of abdominal pain during preg-

nancy, occurring in 0.1–1% of pregnancies and occurring most commonly in the third trimester [3]. In pregnancy, gallstones are the most common cause of pancreatitis because pregnancy promotes the formation of sludge and stones within the gall-bladder due to increased cholesterol synthesis, bile stasis, and decreased gallbladder contraction. In addition, higher levels of maternal estrogen in the third trimester can increase triglycer-ide synthesis and, in some cases, can induce pancreatitis sec-ondary to hypertriglyceridemia. Increased intraabdominal pressure on the bile ducts in the third trimester has also been proposed as a potential reason for the reported increased inci-dence of pancreatitis in the third trimester [4, 76].

AJR:194, June 2010 WS25


In the nonpregnant population, contrast-enhanced CT is usually the study of choice for evaluating complications of pancreatitis. However, during pregnancy ultrasound can first be used to search for the cause and complications of pancreatitis including choledocholithiasis and pseudocyst formation. If ultrasound is normal or indeterminate, MRI with multiplanar T2-weighted SSFSE and axial T1-weight-ed sequences and MR cholangiopancreatography (MRCP) with heavily T2-weighted sequences can be performed to confirm the diagnosis of pancreatitis and to search for causes and complications of pancreatitis (Fig. 12). Screen-

ing the biliary tree for possible stones with MRCP can also help avoid or guide a more invasive ERCP procedure, thus minimizing maternal and fetal risk and exposure to ionizing radiation [13].

Genitourinary CausesUrinary tract causes of pain during pregnancy include

physiologic and obstructive hydronephrosis and infectious causes such as cystitis and pyelonephritis, which do not usually require imaging for diagnosis and treatment. The incidence of urolithiasis is not increased during pregnancy. However, the

A

C

Fig. 13—Obstructive hydronephrosis in 23-year-old pregnant woman who presented with left flank pain. A, Sagittal gray-scale ultrasound image of left kidney shows mild hydronephrosis (arrow). B, Transverse color Doppler ultrasound image through bladder shows right ureteral jet (arrow) but absence of left ureteral jet. Neither left ureteral calculus nor dilatation of left ureter was seen sonographically.C, Subsequent unenhanced CT image reveals 2-mm calculus (arrow) at left ureterovesical junction.

B

Woodfield et al.

WS26 AJR:194, June 2010

approach to imaging urolithiasis and the need to differentiate between physiologic and obstructive hydronephrosis differs between pregnant and nonpregnant patients.

HydronephrosisObstructive hydronephrosis typically presents in the sec-

ond or third trimester and is most commonly caused by uri-nary tract calculi [13]. Urolithiasis is reportedly detected in 1 in 90 to 1 in 3,800 pregnancies and occurs more commonly in multipara pregnancies with equal involvement of the right and left sides [2]. Hospitalization for pain manage-ment is often required for pregnant patients with symptom-atic urolithiasis, although 70–80% of all obstructive calculi will spontaneously pass with conservative management [2].

Potential complications of urolithiasis include pyelonephri-tis and premature labor induced by renal colic with or with-out concomitant infection.

Physiologic dilatation of the collecting system, which oc-curs in up to 90% of pregnant patients, can mimic obstructive hydronephrosis clinically and can delay accurate diagnosis [2]. Physiologic hydronephrosis is usually asymptomatic, but it can present with abdominal pain and functional ureteral obstruction [77]. Physiologic dilatation of the renal pelvis and ureter, the major pitfall in the assessment of urolithiasis in pregnant patients, is due to the combination of hormone-related relaxation of the ureters during pregnancy and ex-trinsic compression of the ureters by the growing uterus and engorged ovarian veins against the iliopsoas muscle [2]. It is

A

C

Fig. 14—Obstructive hydronephrosis in 31-year-old pregnant woman who presented with right flank pain. A, Sagittal gray-scale ultrasound image of right kidney shows mild hydronephrosis (arrow). No right-sided perinephric fluid, calculus, ureteral dilatation, or ureteral jet is seen. Subsequent MR examination of abdomen and pelvis was performed 1 day later to further differentiate between obstructive versus physiologic right hydronephrosis. B and C, Coronal T2-weighted single-shot fast spin-echo MR images through abdomen illustrate moderate right perinephric fluid (arrows, B) and mild right hydroureteronephrosis (arrows, C) with abrupt termination of dilated right ureter at level of pelvic rim (arrowhead, C); these findings are suggestive of obstructive right hydroureteronephrosis. Ureteral calculus was not visible on MR examination. Patient subsequently passed 3-mm calculus.

B

AJR:194, June 2010 WS27


more commonly seen on the right ureter because of relative protection of the left ureter by the sigmoid colon.

Ultrasound is usually the first imaging technique of choice for evaluating hydronephrosis and urolithiasis dur-ing pregnancy with reported sensitivities for renal and ure-teral calculi ranging between 34% and 95% [78, 79]. Ultra-sound may directly show calculi or reveal secondary findings of acute obstruction such as hydronephrosis with peri-nephric fluid or an absent ureteral jet. The absence of the ureteral jet on the suspected side of obstruction is reported to have a sensitivity of 100% and a specificity of 91% for the diagnosis of obstructive hydronephrosis and indicates complete obstruction [80] (Fig. 13). However, an absent ureteral jet has also been reported in approximately 15% of asymptomatic pregnant women [81]. To decrease false-pos-itive results of absent ureteral jets, patients can be imaged in the contralateral decubitus position (i.e., left posterior oblique to visualize the right ureteral jet) to decrease gravid uterus mass effect on the bladder and ureter. Transvaginal ultrasound and transverse images through the bladder can also facilitate detection of distal ureteral calculi.

Using Doppler ultrasound, the intrarenal resistive index (RI) can be calculated. This value may aid in differentiating between physiologic hydronephrosis and pathologic hydro-nephrosis because normal pregnancy does not usually affect the intrarenal RI; an elevated RI (> 0.70) should be consid-ered abnormal. The elevation in the RI usually occurs within 6 hours after acute obstruction of the collecting system. The RI as a test for diagnosing obstructive hydronephrosis in pregnancy has a reported sensitivity, specificity, and accura-cy of 45%, 91%, and 87%, respectively. However, a differ-ence of 0.40 or greater between the RIs of the normal kidney and the abnormal kidney (ΔRI) is reportedly a better indica-tion of obstruction in the kidney with the higher RI [82]. The sensitivity, specificity, and accuracy of ΔRI for diagnos-ing acute unilateral ureteral obstruction in pregnant women are reported to be 95%, 100%, and 99%, respectively [82].

Ultrasound has the advantages of being portable and noninvasive and not exposing the pregnant patient to ion-izing radiation or IV contrast material. However, maternal body wall acoustics, the gravid uterus, and overlying bowel gas often limit visualization of the ureter. Therefore, a nor-mal or indeterminate renal ultrasound examination may require additional imaging if there is strong clinical suspi-cion for urolithiasis.

Further imaging options may depend on the stage of ges-tation. To limit radiation exposure to the developing fetus, some authors have suggested a limited IV urography ex-amination consisting of a scout film, 10-minute film, and minimal number of additional films if the patient is less than 24 weeks’ gestation and a low-dose CT examination using a low-dose renal calculus protocol if the patient is greater than 24 weeks’ gestation [83]. The high sensitivity (> 95%) and specificity (> 98%) of CT for detecting urinary

tract calculi as small as 1–2 mm make CT typically the first imaging technique of choice in nonpregnant patients and the second imaging technique of choice in pregnant pa-tients for diagnosing urolithiasis [13].

MR urography (MRU) with T2-weighted imaging has also been reported to have a high sensitivity for the detection of urinary tract dilatation and for the identification of the site of obstruction. MRU can also help differentiate between physiologic hydronephrosis and obstructive hydronephrosis [84]. Features of obstructive hydronephrosis with MRI in-clude renal enlargement, perinephric fluid, and an abrupt change in the caliber of the ureter above or below the uterus (Fig. 14). In contrast, physiologic hydronephrosis on MRU is characterized by gradual, smooth tapering of the mid ureter due to extrinsic compression between the gravid uterus and iliopsoas muscle [84] (Fig. 15). MRI is also particularly help-ful in revealing complications of pyelonephritis. However, it remains a useful second-line examination largely because of its limited ability in detecting small calculi and characteriz-ing the exact size and shape of calculi.

Vascular CausesVascular causes of abdominal pain that have a higher inci-

dence in pregnancy include venous thromboembolic disease, gonadal vein dilatation, and splenic artery aneurysm rupture.

Venous Thromboembolic DiseaseBoth venous stasis and hypercoagulability place preg-

nant patients at increased risk for venous thrombosis. Ve-nous stasis begins in the first trimester and peaks around 36 weeks of gestation and is likely due to a combination of progesterone-induced venodilation, pelvic venous compres-sion by the gravid uterus, and pulsatile compression of the left iliac vein by the right iliac artery [85]. The hypercoagu-lable state of pregnancy results from the fact that the he-mostatic system is progressively activated to prepare the patient for the hemostatic challenge of delivery.

Most venous thromboembolic events occur in the lower extremities. However, pregnant patients are also at in-creased risk for pelvic, hepatic (Budd-Chiari syndrome), mesenteric, and gonadal venous thrombi. Mesenteric ve-nous thrombosis is particularly ominous because it can re-sult in bowel infarction and because it is difficult to diag-nose given that patients typically present with insidious onset of poorly localized abdominal pain and nonspecific findings on physical examination [3]. Color Doppler ultra-sound can diagnose hepatic thrombosis or occlusion, but the role of ultrasound for the diagnosis of pelvic, mesen-teric, and gonadal venous thrombosis is limited. MRI or contrast-enhanced CT can diagnose abdominal and pelvic venous thrombosis (Fig. 10B). In the pregnant patient, de-pending on institution experience and MR availability, MR venography (MRV) may be the preferred imaging test be-cause MRV avoids the use of radiation and can be per-

Woodfield et al.

WS28 AJR:194, June 2010

formed without the use of IV contrast material. Both time-of-flight and true FISP MR sequences can detect flow and depict thrombus in abdominal and pelvic vessels. However, unenhanced sequences can be limited by flow signal arti-facts [86]. Treatment of thromboembolic disease during pregnancy requires systemic anticoagulation therapy.

Gonadal Vein SyndromeEnlargement of the right gonadal vein in the late second

and third trimesters of pregnancy has also been reported as a potential cause of abdominal pain [65]. Dilatation of the gonadal vein itself or the resulting extrinsic compression of the ureter by the enlarged gonadal vein has been referred to as “right ovarian vein syndrome” [65]. Rarely, subsequent rupture of the dilated right ovarian vein during pregnancy has been described [87]. Right ovarian vein dilatation is like-ly a diagnosis of exclusion when it is the only finding on ul-trasound, MRI, or CT to account for a pregnant patient’s right-sided pain (Fig. 16).

Splenic Artery AneurysmPregnancy is a major risk factor for the rupture of a splenic

artery aneurysm, particularly in the third trimester or during labor. It has been theorized that hormonal changes during pregnancy alter the elastic properties of the arterial wall [88]. Splenic artery aneurysms are usually asymptomatic but can occasionally present as vague epigastric or left upper quadrant pain. If a splenic artery aneurysm ruptures, it can be a cata-strophic event associated with both maternal and fetal mor-tality. Therefore, if a splenic artery aneurysm is detected inci-dentally in a woman of child-bearing age, elective treatment with splenectomy, artery resection, aneurysm exclusion, or aneurysm embolization is recommended even if the patient is asymptomatic [3, 89]. Splenic artery aneurysms can be de-tected on abdominal ultrasound, CT, or MRI.

References 1. Firstenberg MS, Malangoni MA. Gastrointestinal surgery during pregnancy.

Gastroenterol Clin North Am 1998; 27:73–88

2. Mayer IE, Hussain H. Abdominal pain in pregnancy. Gastroenterol Clin North

Fig. 15—Physiologic hydronephrosis in 22-year-old pregnant woman who presented with persistent right flank pain radiating inferiorly. Sagittal T2-weighted single-shot fast spin-echo MR image through abdomen and pelvis shows mild dilatation of right ureter with gradual, smooth tapering of distal ureter (arrow) between posterior gravid uterus and iliopsoas muscle. These findings are consistent with physiologic hydronephrosis, which is normal finding of pregnancy that can cause abdominal pain and can be confused with obstructive hydronephrosis.

Fig. 16—Gonadal vein syndrome in 27-year-old pregnant woman who presented with right-sided abdominal pain. Axial time-of-flight MR image shows patent but dilated gonadal veins, with dilatation of right (long arrow) being greater than left (short arrow) vein. Given that no other reason for abdominal pain was evident on MR examination or clinically, patient’s pain was attributed to dilatation of right gonadal vein. Also note patency but compression of inferior vena cava (arrowhead) by gravid uterus.

AJR:194, June 2010 WS29


Am 1998; 27:1–36

3. Cappell MS, Friedel D. Abdominal pain during pregnancy. Gastroenterol Clin North Am 2003; 32:1–58

4. Sharp HT. The acute abdomen during pregnancy. Clin Obstet Gynecol 2002; 45:405–413

5. Melnick DM, Wahl WL, Dalton VK. Management of general surgical prob-lems in the pregnant patient. Am J Surg 2004; 187:170–180

6. Oto A, Ernst RD, Shah R, et al. Right lower quadrant pain and suspected ap-pendicitis in pregnant women: evaluation with MR imaging: initial experience. Radiology 2005; 234:445–451

7. Pedrosa I, Levine D, Eyvazzadeh AD, Siewert B, Ngo L, Rofsky NM. MR imaging of acute appendicitis in pregnancy. Radiology 2006; 238:891–899

8. Birchard KR, Brown MA, Hyslop WB, Firat Z, Semelka RC. MRI of acute abdominal and pelvic pain in pregnant patients. AJR 2005; 184:452–458

9. Kanal E, Barkovich AJ, Bell C, et al.; ACR Blue Ribbon Panel on MR Safety. ACR guidance document for safe MR practices: 2007. AJR 2007; 188:1447–1474

10. American College of Radiology Website. ACR practice guideline for imaging pregnant or potentially pregnant adolescents and women with ionizing radia-tion. www.acr.org/SecondaryMainMenuCategories/quality_safety/guidelines/dx/Pregnancy.aspx. Published 2008. Accessed on February 21, 2010

11. Sudah M, Vanninen RL, Partanen K, et al. Patients with acute flank pain: com-parison of MR urography with unenhanced helical CT. Radiology 2002; 223:98–105

12. Lazarus E, Mayo-Smith WW, Mainiero MB, Spencer PK. CT in the evaluation of nontraumatic abdominal pain in pregnant women. Radiology 2007; 244:784–790

13. Patel SJ, Reede DL, Katz DS, Subramaniam R, Amorosa JK. Imaging the preg-nant patient for nonobstetric conditions: algorithms and radiation dose consid-erations. RadioGraphics 2007; 27:1705–1722

14. Rodesch F, Camus M, Ermans AM, Dodion J, Delange F. Adverse effect of amniofetography on fetal thyroid function. Am J Obstet Gynecol 1976; 126:723–726

15. Atwell TD, Lteif AN, Brown DL, et al. Neonatal thyroid function after admin-istration of IV iodinated contrast agent to 21 pregnant patients. AJR 2008; 191:268–271

16. American College of Radiology Website. Manual on contrast media. www.acr.org/SecondaryMainMenuCategories/qualitysafety/contrast_manual.aspx. Pub-lished 2008. Accessed February 22, 2010

17. Wilcox AJ, Weinberg CR, O’Conner JF, et al. Incidence of early loss of preg-nancy. N Engl J Med 1988; 319:189–194

18. Laing FC, Frates MC, Benson CB. Ultrasound evaluation during the first tri-mester of pregnancy. In: Callen PW, ed. Ultrasonography in obstetrics and gynecology, 5th ed. Philadelphia, PA: Saunders, 2008:181–224

19. Rowling SE, Langer JE, Coleman BG, et al. Sonography during early preg-nancy: dependence of threshold and discriminatory values on transvaginal transducer frequency. AJR 1999; 172:983–988

20. Levi CS, Lyons EA, Lindsay DJ. Early diagnosis of nonviable pregnancy with endovaginal US. Radiology 1988; 167:383–385

21. Rowling SE, Coleman BG, Langer JE, et al. First-trimester US parameters of failed pregnancy. Radiology 1997; 203:211–217

22. Nyberg DA, Laing FC, Filly RA. Threatened abortion: sonographic distinction of normal and abnormal gestation sacs. Radiology 1986; 158:397–400

23. Doubilet PM, Benson CB. Embryonic heart rate in the early first trimester: what rate is normal? J Ultrasound Med 1995; 14:431–434

24. Bree RL, Edwards M, Böhm-Veléz M, Beyler S, Roberts J, Mendelson EB. Transvaginal sonography in the evaluation of normal early pregnancy: correla-tion with HCG level. AJR 1989; 153:75

25. Centers for Disease Control and Prevention (CDC). Current Trends Ectopic Pregnancy: United States, 1990–1992. MMWR 1995; 44:46–48

26. Maymon R, Shulman A. Controversies and problems in the current manage-ment of tubal pregnancy. Hum Reprod Update 1996; 2:541–551

27. Clayton HB, Schieve LA, Peterson HB, et al. Ectopic pregnancy risk with as-sisted reproductive technology procedures. Obstet Gynecol 2006; 107:595–604

28. Fernandez H, Gervaise A. Ectopic pregnancies after infertility treatment: mod-ern diagnosis and therapeutic strategy. Hum Reprod Update 2004; 10:503–513

29. Goldman GA, Fisch B, Ovadia J, Tadir Y. Heterotopic pregnancy after assisted reproductive technologies. Obstet Gynecol Surv 1992; 47:217–221

30. Brown DL, Doubilet PM. Transvaginal sonography for diagnosing ectopic pregnancy: positivity criteria and performance characteristics. J Ultrasound Med 1994; 13:259–266

31. Nyberg DA, Mack LA, Jeffrey RB Jr, Laing FC. Endovaginal sonographic evalu-ation of ectopic pregnancy: a prospective study. AJR 1987; 149:1181–1186

32. Cacciatore B. Can the status of tubal pregnancy be predicted with transvaginal sonography? A prospective comparison of sonographic, surgical, and serum hCG findings. Radiology 1990; 177:481–484

33. Nyberg DA, Hughes MP, Mack LA, Wang KY. Extrauterine findings of ectopic pregnancy at transvaginal US: importance of echogenic fluid. Radiology 1991; 178:823–826

34. Jung SE, Byun JY, Lee JM, et al. MR imaging of maternal diseases in preg-nancy. AJR 2001; 177:1293–1300

35. Nyberg DA, Mach LA, Benedetti TJ, Cyr DR, Schuman WP. Placental abrup-tion and placental hemorrhage: correlation of sonographic findings with fetal outcome. Radiology 1987; 164:357–361

36. Nyberg DA, Cyr DR, Mack LA, Wilson DA, Shuman WP. Sonographic spec-trum of placental abruption. AJR 1987; 148:161–164

37. Trop I, Levine D. Hemorrhage during pregnancy: sonography and MR imag-ing. AJR 2001; 176:607–615

38. Iams JD, Goldenberg RL, Meis PJ, et al. The length of the cervix and the risk of spontaneous premature delivery: National Institute of Child Health and Hu-man Development Maternal Fetal Medicine Unit Network. N Engl J Med 1996; 334:567–572

39. Hibbard JU, Tart M, Moawad AH. Cervical length at 16–22 weeks gestation and risk for preterm delivery. Obstet Gynecol 2000; 96:972–978

40. Murakawa H, Utumi T, Hasegawa I, Tanaka K, Fuzimori R. Evaluation of threatened preterm delivery by transvaginal ultrasonographic measurement of cervical length. Obstet Gynecol 1993; 82:829–832

41. Rooholamini SA, Au AH, Hansen GC, et al. Imaging of pregnancy-related complications. RadioGraphics 1993; 13:753–770

42. Schmeler KM, Mayo-Smith WW, Peipert JF, et al. Adnexal masses in pregnancy: surgery compared with observation. Obstet Gynecol 2005; 105:1098–1103

43. Chang HC, Bhatt S, Dogra VS. Pearls and pitfalls in diagnosis of ovarian tor-sion. RadioGraphics 2008; 28:1355–1368

44. Eyvazzadeh AD, Levine D. Imaging of pelvic pain in the first trimester of preg-nancy. Radiol Clin North Am 2006; 44:863–877

45. Chiang G, Levine D. Imaging of adnexal masses in pregnancy. J Ultrasound Med 2004; 23:805–819

46. Bromley B, Benaccerraf B. Adnexal masses during pregnancy: accuracy of sonographic diagnosis and outcome. J Ultrasound Med 1997; 16:447–452

47. Ribic-Pucelj M, Kobal B, Peternelj-Marinsek S. Surgical treatment of adnexal masses in pregnancy: indications, surgical approach and pregnancy outcome. J Reprod Med 2007; 52:273–279

48. Smorgick N, Pansky M, Feingold M, et al. The clinical characteristics and sonographic findings of maternal ovarian torsion in pregnancy. Fertil Steril 2009; 92:1983–1987; Epub Nov. 5, 2008

49. Stark JE, Siegel MJ. Ovarian torsion in prepubertal and pubertal girls: sono-graphic findings. AJR 1994; 163:1479–1482

50. Rosado WM Jr, Trambert MA, Gosink BB, Pretorius DH. Adnexal torsion: diagnosis by using Doppler sonography. AJR 1992; 159:1251–1253

51. Lev-Toaff AS, Coleman BG, Arger PH, et al. Leiomyomas in pregnancy: sono-graphic study. Radiology 1987; 164:375–380

52. Kawakami S, Togashi K, Konishi I, et al. Red degeneration of uterine leiomy-oma: MR appearance. J Comput Assist Tomogr 1994; 18:925–928

53. Tamir IL, Bongard FS, Klein SR. Acute appendicitis in the pregnant patient. Am J Surg 1990; 160:571–576

54. Oto A, Srinivasan PN, Ernst RD, et al. Revisiting MRI for appendix location during pregnancy. AJR 2006; 186:883–887

55. Rettenbacher T, Hollerweger A, Macheiner P, et al. Outer diameter of the ver-miform appendix as a sign of acute appendicitis: evaluation at US. Radiology 2001; 218:757–762

56. Jeffrey RB, Jain KA, Nghiem HV. Sonographic diagnosis of acute appendicitis:

Woodfield et al.

WS30 AJR:194, June 2010

interpretive pitfalls. AJR 1994; 162:55–59

57. Lim HK, Bae SH, Seo GS. Diagnosis of acute appendicitis in pregnant women: value of sonography. AJR 1992; 159:539–542

58. Wise SW, Labuski MR, Kasales CJ, et al. Comparative assessment of CT and sonographic techniques for appendiceal imaging. AJR 2001; 176:933–941

59. Johansson EP, Rydh A, Riklund KA. Ultrasound, computed tomography, and labo-ratory findings in the diagnosis of appendicitis. Acta Radiol 2007; 48:267–273

60. Israel GM, Malguria N, McCarthy S, Copel J, Weinreb J. MRI vs ultrasound for suspected appendicitis during pregnancy. J Magn Reson Imaging 2008; 28:428–433

61. Poortman P, Lohle PN, Schoemaker CM, et al. Comparison of CT and sonog-raphy in the diagnosis of acute appendicitis: a blinded prospective study. AJR 2003; 181:1355–1359

62. Gaitini D, Beck-Razi N, Mor-Yosef D, et al. Diagnosing acute appendicitis in adults: accuracy of color Doppler sonography and MDCT compared with sur-gery and clinical follow-up. AJR 2008; 190:1300–1306

63. Mourad J, Elliott JP, Erickson L, Lisboa L. Appendicitis in pregnancy: new information that contradicts long-held clinical beliefs. Am J Obstet Gynecol 2000; 182:1027–1029

64. Cobben LP, Groot I, Haans L, Blickman JG, Puylaert J. MRI for clinically suspected appendicitis during pregnancy. AJR 2004; 183:671–675

65. Pedrosa I, Zeikus EA, Levine D, et al. MR imaging of acute right lower quad-rant pain in pregnant patients and nonpregnant patients. RadioGraphics 2007; 27:721–753

66. Raman SS, Lu DS, Kadell BM, Vodopich DJ, Sayre J, Cryer H. Accuracy of nonfocused helical CT for the diagnosis of acute appendicitis: a 5-year review. AJR 2002; 178:1319–1325

67. Worlicek H, Lutz H, Heyder N, Matek W. Ultrasound findings in Crohn’s disease and ulcerative colitis: a prospective study. J Clin Ultrasound 1987; 15:153–163

68. Haggett PJ, Moore NR, Shearman JD, Travis SP, Jewell DP, Mortensen NJ. Pelvic and perineal complications of Crohn’s disease: assessment using mag-netic resonance imaging. Gut 1995; 36:407–410

69. Furukawa A, Saotome T, Yamasaki M, et al. Cross-sectional imaging in Crohn disease. RadioGraphics 2004; 24:689–702

70. Maccioni F, Colaiacomo MC, Parlanti S. Ulcerative colitis: value of MR imag-ing. Abdom Imaging 2005; 30:584–592

71. Perdue PW, Johnson HW Jr, Stafford PW. Intestinal obstruction complicating pregnancy. Am J Surg 1992; 164:384–388

72. Davis MR, Bohon CJ. Intestinal obstruction in pregnancy. Clin Obstet Gynecol

1983; 26:832–842

73. Regan F, Beall DP, Bohlman ME, Khazan R, Sufi A, Schaefer DC. Fast MR im-aging and the detection of small-bowel obstruction. AJR 1998; 170:1465–1469

74. Nunes JO, Turner MA, Fulcher AS. Abdominal imaging features of HELLP syndrome: a 10-year retrospective review. AJR 2005; 185:1205–1210

75. Castro MA, Ouzounian JG, Colletti PM, Shaw KJ, Stein SM, Goodwin TM. Radiologic studies in acute fatty liver of pregnancy: a review of the literature and 19 new cases. J Reprod Med 1996; 41:839–843

76. Bzowej NH. Gastrointestinal complications of pregnancy. In: Grendell JH, Friedman SL, McQuaid KR, eds. Current diagnosis & treatment in gastroen-terology. New York, NY: McGraw-Hill, 2003:183–185

77. Puskar D, Balagovic I, Filipovic A, et al. Symptomatic physiologic hydronephrosis in pregnancy: incidence, complications and treatment. Eur Urol 2001; 39:260–263

78. Parulkar BG, Hopkins TB, Wollin MR, Howard PJ, Lal A. Renal colic during pregnancy: a case for conservative treatment. J Urol 1998; 159:365–368

79. Stothers L, Lee LM. Renal colic in pregnancy. J Urol 1992; 148:1383–1387

80. Deyoe LA, Cronan JJ, Breslaw BH, Ridlen MS. New techniques of ultrasound and color Doppler in the prospective evaluation of acute renal obstruction: do they replace the intravenous urogram? Abdom Imaging 1995; 20:58–63

81. Wachsberg RH. Unilateral absence of ureteral jets in the third trimester of preg-nancy: pitfall in color Doppler US diagnosis of urinary obstruction. Radiology 1998; 209:279–281

82. Shokeir AA, Mahran MR, Abdulmaaboud M. Renal colic in pregnant women: role of renal resistive index. Urology 2000; 55:344–347

83. Fielding JR, Washburn D. Imaging the pregnant patient: a uniform approach. J Women’s Imaging 2005; 7:16–21

84. Spencer JA, Chahal R, Kelly A, Taylor K, Eardley I, Lloyd SN. Evaluation of painful hydronephrosis in pregnancy: magnetic resonance urographic patterns in physiologic dilatation versus calculus obstruction. J Urol 2004; 171:256–260

85. Greer IA. Thrombosis in pregnancy: maternal and fetal issues. Lancet 1999; 353:1258–1265

86. Nagayama M, Watanabe Y, Okumura A, Amoh Y, Nakashita S, Dodo Y. Fast MR imaging in obstetrics. RadioGraphics 2002; 22:563–580

87. Renuka T, Dhaliwal LK, Gupta I. Hemorrhage from ruptured utero-ovarian veins during pregnancy. Int J Gynaecol Obstet 1998; 60:167–168

88. Stanley JC, Fry WJ. Pathogenesis and clinical significance of splenic artery aneurysms. Surgery 1974; 76:898–909

89. Parangi S, Levine D, Henry A, Isakovich N, Pories S. Surgical gastrointestinal disorders during pregnancy. Am J Surg 2007; 193:223–232

F O R Y O U R I N F O R M A T I O N

The reader’s attention is directed to the Self-Assessment-Module for this article, which appears on page S42.

abdominal pain in pregnancy: diagnoses and imaging unique to

Documents