ENDOLUMINAL CONTRAST FOR ABDOMEN AND PELVIS MRI: WHEN, WHERE, AND HOW?Mohit Gupta, MD; Gaurav Khatri, MD; April Bailey, MD; Daniella F. Pinho, MD; and Ivan Pedrosa, MD

Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA

PURPOSE

ENDORECTAL CONTRAST

INTRAVESICAL CONTRAST

ENDOVAGINAL CONTRAST

CONCLUSION

REFERENCES

ORAL CONTRAST

• Describe the various endoluminal contrast agents available for magnetic resonance (MR) imaging in the abdomen and pelvis.

• Highlight specific clinical scenarios where endoluminal contrast agents may help delineate anatomy and identify pathology.

• Illustrate incorporation of endoluminal contrast agents into clinical protocols and workflow for MR imaging of the abdomen and pelvis.

ULTRASOUND GEL • Shown to improve performance of MR defecography. • Although controversial, may be valuable in rectal cancer patients with small tumors, polypoid tumors, and history of prior treatment. • May falsely decrease distance between rectal tumor and mesorectal fascia (circumferential resection margin) – not recommended for low tumors. • Technique – Patient is placed in left lateral decubitus position; 60-120 mL of warm ultrasound gel instilled via catheter-tip syringe.

GADOLINIUM ENEMA • Detection of intraluminal manifestations or small occult sinus tracts/fistulae in inflammatory conditions not apparent on traditional CT or MRI. • Technique – 1:100 concentration; 5 mL of gadolinium in 500 mL of saline via rubber Foley catheter which is placed to gravity.

GADOLINIUM (MR CYSTOGRAM)

• Bladder tumor detection.

• Complications of tumor, radiation, trauma such as leak, fistulae, or sinus tract formation.

• May be utilized in patients that have contraindication to CT examination or iodine.

• Technique – Precontrast imaging, followed by instillation of 1:100 concentration of gadolinium (5 mL in 500mL of saline) via rubber Foley catheter which is placed to gravity.

SALINE (MR CYSTOGRAM)

• For patients with contrast allergies. Good distention although saline cannot be distinguished from urine.

ULTRASOUND GEL • Provides stable expansion of the vagina. • Improves delineation of the vaginal fornices and cervix. • Potential applications:

■ Congenital anomalies – septate uterus and vaginal septum.

■ Pelvic malignancy – staging and recurrence. ■ Deep endometriosis – identify posterior implants difficult to otherwise diagnose due to tight anatomic space.

■ Fistula delineation – potential complication of pelvic radiation, trauma, infection and inflammation.

♦ Fistula may be too small to depict significant amount of signal intensity on T2-weighted imaging without luminal contrast.

• Technique – Instill approximately 30-60 mL of sterile ultrasound gel via a catheter-tip syringe into the vagina.

• Various options and opportunities for use of intraluminal contrast in MR imaging.

• In certain examinations (MR enterography, MR defecography), the use of intraluminal contrast is imperative.

• In other cases, may help with the detection of subtle pathology in the abdomen and pelvis.

• Proper use requires knowledge of appropriate indications, patient preparation, and selection of a proper imaging protocol.

1. Brant WE, Lambert DL. Gastrointestinal Tract, Peritoneal Cavity, and Spleen MR Imaging. In “Essentials of Body MRI”. Eds. Brant WE, de Lange E. Oxford University Press New York 2012.

2. Pannu HK, Scatarige JC, Eng J. Comparison of Supine Magnetic Resonance Imaging With and Without Rectal Contrast to Fluoroscopic Cystocolpoproctography for the Diagnosis of Pelvic Organ Prolapse. Journal of Computer Assisted Tomography. 2009;33:125-30.

3. Fiaschetti V, Crusco S, Meschini A, et al. Deeply infiltrating endometriosis: evaluation of retro-cervical space on MRI after vaginal opacification. European Journal of Radiology 2012. 81: 3638-3645

4. Kaur H, Choi H, You Y, et al. MR imaging for preoperative evaluation of primary rectal cancer: practical considerations. Radiographics 2012; 32: 389-409

5. Olpin J, Hellbrun M. Imaging of Mullerian duct anomalies. Clin Obstet Gynecol 2009; 52 (1): 40-56.

6. Romero M, Buxbaum J, and Palmer S. Magnetic resonance imaging of the gut: a primer for the luminal gastroenterologist. Am J Gastroenterol 2014; 109: 497-509.

POSITIVE ENTERIC AGENTS • Limited use due to artifact on T1-weighted images and poor identification of intraluminal pathology and subtle mucosal/wall enhancement.

NEGATIVE ENTERIC AGENTS • Limited use due to availability, cost, and patient tolerance. Oral ferumoxsil used to reduce the signal from surrounding bowel on MRCP (not currently available in the US).

BIPHASIC ENTERIC AGENTS • Most commonly used due to good delineation of both luminal and wall pathology.

■ Water, Polyethylene Glycol (PEG), low-concentration barium sulfate (Volumen®, E-Z-EM, Westbury, NY).

• Potential applications ■ Intraluminal and extraluminal manifestations of inflammatory bowel disease (wall thickening, mucosal abnormalities, strictures, fistulae, leaks).

■ Delineate bowel neoplasms and autoimmune diseases.

• Technique ■ Ingest 900cc of barium sulfate solution over 45minutes followed by 450cc of water prior to start of exam.

Table 1: Endoluminal Contrast Agents

Figure 1A and 1B. Coronal 2D thick slab heavily T2-weighted single shot fast spin echo (SSFSE) image obtained after oral administration of 900 mL of barium-based oral contrast (Volumen®) followed by 450 mL of water in a patient with active Crohn’s disease depicts luminal narrowing in the terminal ileum (blue arrows) due to severe wall thickening/inflammation, demonstrated in other sequences (not shown). Similar T2-weighted SSFE acquisition in a second patient with Crohn’s disease after ingestion of oral contrast preparation demonstrates an enterocolic fistula (red arrow) in the right lower quadrant.

Figure 4A and 4B. 26 year-old female with Peutz-Jegher’s Syndrome. Coronal bSSFP image performed after ingestion of 900 mL of barium-based oral contrast and 450 mL of water depicts polypoid filling defect in a lower abdominal bowel loop (A). Coronal post contrast fat suppressed T1-weighted 3D SPGR image after administration of 5 mL gadolinium confirms an enhancing 3cm polyp in the small bowel (B). 1 mg of glucagon was administered for anti-peristaltic effect prior to acquisition of these images.

Figure 5A-D. 62 year-old male with active colitis. Axial contrast enhanced CT (A) demonstrates moderate bowel wall thickening of the sigmoid colon with pericolonic inflammation. Axial T2-weighted (T2W) Fast Spine Echo (FSE) image (B) demonstrates similar findings to CT with wall thickening and heterogeneous signal intensity in the wall. Maximum intensity projection (MIP) reconstructions of T1-weighted 3D SPGR acquisitions after rectal administration of diluted gadolinium shows severe irregularity of the sigmoid (arrows in C) and a “double-track” sign due to intramural sinus tract formation (arrows in D) which was not readily apparent on CT exam or on the T2-weighted FSE image.

Figure 3. Contrast-enhanced axial CT (A) performed in a male with acute abdominal pain shows a possible nodular hyperdense area of wall thickening (red arrow in A) along the greater curvature of the stomach (not shown) surrounded by hyperdense fluid, consistent with hemoperitoneum (yellow arrows). Sagittal balanced steady-state free-precession (bSSFP) MRI performed a few weeks later using water as oral contrast agent provided adequate distension and increased intraluminal signal intensity to confirm the existence of a submucosal nodule (arrow in B) in the gastric wall. Gadolinium-enhanced sagittal fat suppressed T1-weighted 3D spoiled gradient echo (SPGR) image confirmed avid enhancement in the nodule (arrow in C). A gastrointestinal stromal tumor was confirmed at histopathology after surgery.

Figure 2. Coronal 2D thick slab heavily T2-weighted SSFSE image obtained after oral administration of 900 mL of barium-based oral contrast (Volumen®) followed by 450 mL of water depicts diffuse smooth bowel wall dilation and “stack of coin” appearance of the proximal bowel folds, consistent with the patient’s suspected diagnosis of scleroderma (i.e. patient had skin lesions consistent with this diagnosis).

Intraluminal And Extraluminal Manifestations of Crohn’s Disease

Peutz-Jegher’s Syndrome

Active Colitis With Intramural Sinus Tract Formation

Gastrointestinal Stromal Tumor (GIST)

Scleroderma

Type of Agent Examples Signal Intensity- T1W images

Signal Intensity -T2W images

Positive Enteric Dilute gadolinium, high-fat milk, ferric ammonium citrate, iron phytate, manganese chloride

Negative Enteric Superparamagnetic Iron Oxide (ferumoxsil), blueberry/pineapple juice

Biphasic Enteric Water, Polyethylene Glcycol (PEG), Barium sulfate, mannitol/sorbitol solutions

Endorectal Ultrasound Gel Gadolinium Enema

Endovaginal Ultrasound Gel

Intravesical Water Gadolinium

Pelvic Organ Prolapse

Deep Endometriosis Figure 7. Sagittal 2D T2-weighted FSE image obtained after endovaginal administration of 60 mL of ultrasound gel demonstrates thickening of the posterior vaginal fornix with hypointense signal intensity. In this patient with recurrent pelvic pain, findings are in keeping with deep pelvic endometriosis (red arrow). Additional endometriosis plaque is seen in the retrouterine space (yellow arrow).

Figure 12. Fat suppressed sagittal T1-weighted 3D SPGR image after instillation of diluted gadolinium (1:100 concentration) via a Foley catheter depicts a vesicovaginal fistula in a 68 year-old female with cervical cancer status-post radiation.

Figure 6A-C. 70 year-old female with suspected cystocele, enterocele, possible rectocele. bSSFP image in the mid-sagittal plane without rectal ultrasound gel during maximal strain (A) demonstrates a small enterocele (red arrow). After instillation of rectal ultrasound gel, bSSFP image in the mid-saggital plane during early defecation (B) demonstrates a moderate rectocele (black arrow). bSSFP image in the mid-sagittal plane during late defecation (C) demonstrates not only a large enterocele (long red arrow), but also rectal intussusception (green arrow) and a small cystocele (yellow arrow). Pubococcygeal line is shown for reference in all three images (blue line).

Complete Septate Uterus With Vaginal Septum

Transverse Vaginal Septum

Stage 1 Cervical Cancer W/O Extension Into Vaginal Fornices

Vesicovaginal Fistula Secondary to Pelvic Radiation for Cervical Cancer

Rectovaginal Fistula Secondary to Pelvic Radiation for Rectal Carcinoma

Figure 8A-F. Coronal (A-D) and axial (E and F) 2D T2-weighted FSE obtained after endoluminal vaginal administration of 60 mL of ultrasound gel in a 30 year-old female with a suspected septate uterus. MRI confirms the septate uterus configuration (A) and continuation of the septum through the external os of the cervix (B). A thick septum is also seen in the vagina (C, D) with a small anterior (E) and a larger posterior (F) component.

Figure 9A and 9B. 33 year-old female with transverse vaginal septum. Sagittal 2D T2-weighted FSE image (A) and coronal reconstruction of a sagittal 3D T2-weighted FSE acquisition (B) demonstrates focal stenosis of the vaginal lumen due to transverse vaginal septum without complete obstruction. Instilled contrast traverses the focal areas of stenosis via a tiny defect (arrows) confirming incomplete septum.

Figure 10. Cervical cancer in a 33-year old female. Sagittal 2D T2-weighted FSE image obtained after administration of 60 mL of endoluminal vaginal ultrasound. There is expansion of the vagina with good delineation of the vaginal fornices (yellow arrows). The cervical tumor (red arrow) does not extend into the fornices. Accurate assessment of degree of vaginal wall invasion without vaginal distention is very challenging in large cervical tumor.

Figure 11. Rectovaginal fistula in a 67-year old female with stage IV rectal carcinoma and history of pelvic radiation. Sagittal 2D T2-weighted FSE image after administration of 60 mL of endoluminal vaginal ultrasound gel depicts a 5 mm wide rectovaginal fistula (arrow) approximately 4.5 cm from the anal verge. Ultrasound gel instilled in the vagina is seen extending into the rectum.

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