perianal fistula crohn
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The Evaluation and Treatment of Crohn Perianal Fistulae: EUA, EUS, MRI, and Other Imaging ModalitiesPaul E. Wise, MDa, David A. Schwartz, MDb,*
KEYWORDS Crohn disease EUS Examination under anesthesia (EUA) Imaging MRI Perianal stulae Setons
Perianal stula, dened as an abnormal communication between the anal canal or lower rectum and the perianal or perineal skin, is among the more morbid manifestations of Crohn disease (CD). The development of a perianal stula is usually accompanied by pain, fever, and purulent drainage, and may even be associated with fecal incontinence. The exact etiology of perianal stulae in CD remains unclear,1 but it signies a more aggressive and refractory disease phenotype.2 As a result, patients with stulizing CD generally experience a lower quality of life than CD patients without perianal involvement.3,4 Nearly one quarter of all patients with CD develop a perianal stula, with stulae being more common in patients with involvement of the rectum.57 Before the introduction of biologic agents, most stulae required some surgical intervention, with more than one third of patients developing recurrent stulae.5 The introduction of antitumor necrosis factor (TNF)- antibodies has given clinicians the most efcacious medication to date for treating perianal stulae. Induction studies using iniximab at weeks 0, 2, and 6 for active CD perianal stulae resulted in cessation of drainage of all the stulae present in 55% of patients who were randomized to the 5 mg/kg dose compared with only 13% of those who received placebo (P .001).8 However, stulae usually start to drain again if the antiTNFmedication is discontinued.9 Studies looking at maintaining cessation of stulaa Department of Surgery, Section of Surgical Sciences, Vanderbilt University Medical Center, 1211 21st Avenue South, Nashville, TN 37232-0252, USA b Inammatory Bowel Disease Clinic, Division of Gastroenterology, Hepatology and Nutrition, Department of Medicine, Vanderbilt University Medical Center, Suite 220, 1211 21st Avenue South, Nashville, TN 37232-0252, USA * Corresponding address. E-mail address: David.A.Schwartz@Vanderbilt.Edu
Gastroenterol Clin N Am 41 (2012) 379 391 doi:10.1016/j.gtc.2012.01.009 gastro.theclinics.com 0889-8553/12/$ see front matter 2012 Elsevier Inc. All rights reserved.
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drainage utilizing the 3 antiTNF- agents currently available (iniximab, adalimumab, and certolizumab) for CD have yielded similar results with about 36% to 39% of patients able to maintain cessation of drainage over a 26- to 54-week study.9 11 Several factors likely contribute to the low maintenance rates of stula healing. Perhaps the 3 most signicant factors contributing to the high stula recurrence rates after initiating antiTNF- medications are (1) not utilizing surgical intervention to maximize the effect of the medications, (2) failure to initially identify all of the stulae or abscesses present and thus the lack of control of stula healing when using antiTNF- agents, and (3) the premature removal of setons before a stula is completely healed. The bodys natural tendency is to try to close the external cutaneous opening of the stula. This process is accelerated when utilizing antiTNF- agents. When this occurs, an abscess and/or secondary or tertiary stula branch can develop. Indeed, the Present and ACCENT 2 studies with iniximab showed that the rate of abscess formation was high with use of the antiTNF- agents (11% and 15%, respectively).8,9 Two retrospective studies showed that the durable stula healing rate could be improved by establishing drainage and controlling stula healing before beginning medical treatment. In the study by Regueiro and colleagues,12 patients in whom an examination under anesthesia (EUA) with seton placement and abscess drainage was performed were signicantly less likely to have a recurrence of their stula compared with those who never had surgical drainage established (44% vs. 79%).12 Similarly, in the series reported by Topstad and co-authors,13 the authors demonstrated a 69% complete stula healing rate in a small number of patients treated with combination surgical and medical therapy. Correctly identifying all of the stulae or abscesses present can be problematic with digital rectal examination or even during EUA in these patients because of the induration and scarring that can be present in association with the perianal disease. In 1 study, the accuracy of digital rectal examination in dening stula anatomy when done by an experienced surgeon was estimated to be only 62%.14 Similarly, around 10% of stulae are misclassied by EUA alone, resulting in the need for repeat surgical intervention in those patients in whom the stula was incorrectly assessed.1 Last, although the stulae usually stop draining within 6 to 12 weeks of initiating antiTNF- therapy, inammatory activity persists for weeks to months within the middle portion of the stula tract. Relying on physical examination alone to determine stula activity inaccurately assesses the patients progress, resulting in premature removal of setons or inappropriate changes in medical therapy. Studies using both ultrasonography and magnetic resonance imaging (MRI) have demonstrated persistent stula activity in nearly all patients even after the third dose in the iniximab induction sequence.1517 Studies have demonstrated that missing occult tracts can result in recurrent stulae, abscesses, and/or convert a simple stula into a complex stulizing process.18,19 If the stulizing process becomes complex, the chance for healing is greatly reduced.12,18,20 To prevent development of a complex stula and increase the chance of closure, it is important to optimize the tools available to assess the perianal pathology. Therefore, treatment should begin with correctly assessing disease activity and perianal anatomy as well as establishing drainage and providing control of the stula, even before starting medical treatment. Ideally this can be accomplished through the use of imaging and by working closely with surgical colleagues (Fig. 1). The purpose of this article is to review the different imaging modalities available for the assessment of perianal CD as well as the various operative techniques and treatment that can be utilized in these patients. In the future, larger (and thus more
Evaluation and Treatment of Crohn Perianal Fistulae
Fig. 1. Algorithm for the treatment of a patient with perianal Crohn stulae. EUA, examination under anesthesia; EUS, endorectal ultrasonography; MRI, magnetic resonance imaging. *Assumes patient has undergone complete history and physical examination and colonoscopy with or without CT enterography. See text for details of surgical options.
adequately powered), multicenter trials are needed to help guide the optimal management strategies of these complex patients.IMAGING MODALITIES FOR INITIAL EVALUATION Fistulography
Fistulography involves inserting a small catheter into the external stula opening and injecting a small amount of radiopaque contrast material into the tract and imaging the stula using uoroscopy. There are several major limitations to this modality. First and most important, stulograms are not able to directly visualize the sphincter complex; thus, one has to infer the stulas anatomy in relation to the pelvic musculature. In addition, stula tracts can be missed owing to the inability of contrast to ll extensions from the primary track, either from inadequate lling or from debris within the track. Fistulography can also be very uncomfortable for the patient and can be difcult technically for the radiologist to even access the tracts at times. Studies assessing the use of stulography have found its accuracy to range from 16% to 50%.21,22 In 1 representative study, the results from stulography were compared with operative ndings in 25 patients.22 Accuracy was 16%, with a false-positive rate of 12%. This study also showed the false-positive results resulted in unnecessary complications in some patients.
Wise & Schwartz
Fig. 2. Rectal EUS showing large trans-sphincteric stula anteriorly (arrow).
Because of these factors, stulography is not widely used in assessment of CD perianal stulae, with the exception of times when a connection to the bladder or vagina is suspected. In these clinical scenarios, extravasation of contrast into the other organs may be more easily demonstrated using stulography.Axial Computed Tomography
Computed tomography (CT) has been widely used for the evaluation of perianal stulae. The main factor limiting CTs accuracy for perianal stulae is its poor spatial resolution in the pelvis, although it is better than that of stulography. In addition, because the tissue characteristics are very similar, it can be difcult to differentiate between a stula tract and inammation using CT imaging. In a small, prospective study of 25 patients, CT was compared with rectal endosonography using a 5-MHz radial probe. The gold standard in this study was either operative ndings or clinical course. They found endosonography to be more accurate than CT (82% vs. 24%).23 CT is primarily used for the assessment of abscesses, uid collections, or other pathology higher in the pelvis or abdomen than for assessment of the perianal tracts themselves.Endoscopic Ultrasonography
Rectal endoscopic ultrasonography (EUS) involves inserting either a rigid or exible radial probe into the distal rectum and anal canal while the patient lies in the left lateral position. Using this modality, stulae appear as hypoechoic round or oval structures, but can be internally hyperechoic if there is air or gas in the stula (Fig. 2). An abscess usually appears as an anechoic or hypoechoic mass in the perianal tissues. Some clinicians also inject hydrogen peroxide into the cutaneous stula openi