Rohini N. Nadgir 1 Jorge A. Soto 1 Klea Dendrinos 2 Brian C. Lucey 1 James M. Becker 3 Francis A. Farraye 2

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1 Nadgir et al. MRI of Complicated Pouchitis Gastrointestinal Imaging Clinical Observations A C M E D E N T U R I C A L I M A G I N G AJR 2006; 187:W386 W X/06/1874 W386 American Roentgen Ray Society Y O Rohini N. Nadgir 1 Jorge A. Soto 1 Klea Dendrinos 2 Brian C. Lucey 1 James M. Becker 3 Francis A. Farraye 2 F Nadgir RN, Soto JA, Dendrinos K, Lucey BC, Becker JM, Farraye FA Keywords: gastrointestinal radiology, inflammatory bowel disease, MRI, pelvic imaging DOI: /AJR Received June 14, 2005; accepted after revision August 30, Department of Radiology, Boston University Medical Center, 88 E Newton St., 2nd Floor, Boston, MA Address correspondence to J. A. Soto (jorge.soto@bmc.org). 2 Department of Gastroenterology, Boston University Medical Center, Boston, MA Department of Surgery, Boston University Medical Center, Boston, MA WEB This is a Web exclusive article. OBJECTIVE. The purpose of this study is to assess the ability of MRI to identify the presence of inflammation related to the pouch reservoir in symptomatic patients with an ileal pouch anal anastomosis who present with clinically suspected complicated pouchitis. CONCLUSION. Initial results suggest that MRI should be considered in patients who have undergone ileal pouch anal anastomosis and present a clinical impression of complicated pouchitis. MRI showed abnormalities consistent with complicated pouchitis in seven of nine examinations, with findings including pouch wall thickening, abnormal wall enhancement, peripouch fluid collection, sinus and fistula tract formation, lymphadenopathy, and peripouch stranding and fatty proliferation. MRI findings of complicated pouchitis should raise the suspicion of Crohn s disease and should prompt further investigation. ouchitis is the most common complication of ileal pouch anal P anastomosis, a surgical procedure performed for patients with ulcerative colitis. The procedure involves total colectomy and rectal mucosectomy followed by creation of a blind ending ileoanal reservoir with anastomosis to the distal ileum. Pouchitis occurs at least once in nearly half of all ileal pouch anal anastomosis patients. Its cause is uncertain but thought to be related to disequilibrium of the bowel flora within the pouch. Patients typically present with frequent watery or bloody stools, abdominal pain, malaise, and fever. The diagnosis is suspected clinically based on symptoms and confirmed with endoscopic and histopathologic findings. The majority of patients improve with medical management alone, including antibiotics and other chemotherapeutic agents [1]. Occasionally, pouchitis can be refractory to medical management or complicated by fistula or abscess formation and require more aggressive therapy. Endoscopic and histologic findings in these more complex cases are not always entirely consistent with the initial clinical impression of ulcerative colitis. Sometimes, because of the activity and behavior of pouch inflammation, a final diagnosis of Crohn s disease is made in these patients. In cases of suspected complicated pouchitis, both CT and fluoroscopic studies are typically used to assess the integrity of the pouch [2, 3]. Barium studies show mucosal detail, whereas CT defines mural involvement, extent of extramucosal disease, and complications of pouchitis. Both examinations, however, involve ionizing radiation. Given the increased risk of radiation exposure in these often young patients who may have frequent relapses, the role of MRI in assessing disease activity in patients with suspected or known inflammatory bowel disease (IBD) is growing [4 8]. Although MRI has been shown to be a reliable technique for identifying disease activity in patients with IBD, there is limited literature to date on MRI evaluation of the postsurgical complicated pouch, specifically in symptomatic patients with an ileal pouch anal anastomosis [9]. The purpose of this study is to assess the ability of MRI to identify the presence of inflammation related to the pouch reservoir in symptomatic patients with an ileal pouch anal anastomosis who present with suspected complicated pouchitis. Materials and Methods In this retrospective study, we included nine MRI examinations of the pelvis performed between November 2001 and November 2004 on nine patients (four men and five women) ranging in age from 30 to 59 years (mean age, 42 years) who had previously undergone ileal pouch anal anastomo- W386 AJR:187, October 2006

TABLE 1: Typical Imaging Parameters for Evaluation of the Ileal Pouch Axial T2 Parameter Axial T2 Coronal T2 Sagittal T2 Axial T1 Axial T1 Sagittal T1 TR (ms) 4,250 4,700 5,700 3,310 730 590 520 280

2 TABLE 1: Typical Imaging Parameters for Evaluation of the Ileal Pouch Axial T2 Parameter Axial T2 Coronal T2 Sagittal T2 Axial T1 Axial T1 Sagittal T1 TR (ms) 4,250 4,700 5,700 3, TE (ms) FOV (cm) Matrix RFOV (%) Slice thickness (mm) Interslice gap (mm) ETL NA NA NA NA 3 2 NSA sis and who presented with clinical suspicion of complicated pouchitis. MRI examinations were performed between 2 and 14 years (mean, 9 years) after the ileal pouch anal anastomosis procedure. Our institution s investigation review board approved this retrospective study and waived the need for consent signature by the patients enrolled. All MRI examinations of the pelvis were performed on a 1.5-T clinical MR scanner (Intera, Philips Medical Systems), equipped with fast imaging subsystems (maximum gradient of 23 mt/m and a maximum slew rate of 105 mt/ms). Quadrature body coils were used for both excitation and signal reception. Patients were imaged in the supine position without specific bowel preparation. Typical imaging parameters for the pouch examination are detailed in Table 1. Gadopentetate dimeglumine (Magnevist, Berlex) was administered at a dose of 0.1 mmol/kg by power injector at a rate of 2 ml/s. IV contrast material was not administered in two examinations because of lack of venous access. All MRI studies were reviewed by two radiologists who specialize in abdominal imaging, and any discrepancies of opinion were resolved by consensus. Images were examined for the following findings as evidence of pouch inflammation: pouch wall thickening (2 mm or greater thickness of pouch wall), abnormal wall enhancement after administration of IV contrast material (enhancement perceived by the reviewer as greater than that of adjacent normal bowel loops), peripouch stranding (T1 dark linear signal surrounding the pouch), peripouch fluid collection, sinus or fistula tract formation (T1 dark, T2 bright linear or tubular structure related to the pouch that enhanced after gadolinium administration), stricture (focal narrowing with proximal dilatation), lymphadenopathy (one lymph node greater than 1 cm in its greatest dimension or three or more peripouch lymph nodes), and peripouch fatty proliferation (excessive fatty tissue surrounding the pouch producing mass effect on adjacent bowel loops). Imaging findings were then compared with endoscopy performed in closest temporal proximity to the MRI examination; all endoscopic evaluations were performed within 3 weeks of the MRI study. Specifically, four MRI studies were performed on the same day as endoscopy; one 16 days before; and one each 2, 6, 12, and 21 days after endoscopy. Active inflammation was endoscopically manifested as one or more of the following: mucosal erythema, friability, and ulceration within the pouch. Sagittal T1 Gradient-Recalled Echo Dynamic Contrast- Enhanced Sagittal T1 Contrast- Enhanced Note = spectral inversion recovery, FOV = field of view, RFOV = rectangular field of view, ETL = echo-train length, NSA = number of signal averages, NA = not applicable. Fig year-old man with pouch. T2 coronal image shows abnormal thickening of pouch wall. Axial T1 Contrast- Enhanced Further correlation was made with biopsy results from specimens obtained at endoscopy if samples were taken. Biopsies were obtained in eight of the nine cases, and pathologic results were tabulated and correlated with the findings of the MRI examination. The following histologic findings were considered to be indicative of active inflammation: architectural distortion, ulceration, and presence of acute inflammatory cells within the epithelium or crypts or both. For this study, the pathologic result was considered the standard of reference for comparison for mucosal disease activity. In the one case in which biopsy was not performed, the endoscopic impression was considered the standard of reference for comparison for mucosal disease. The patients final diagnoses of ulcerative colitis or Crohn s disease were also recorded. Results MRI showed mucosal disease (pouch wall thickening and enhancement) in five of the nine patients and was confirmed by both endoscopic and pathologic impressions in all five cases. MRI showed findings of extramucosal disease (peripouch fat stranding, fluid collection, fistula or sinus tract formation, lymphadenopathy, fatty proliferation) in seven of the nine patients. Thus, two patients with normal pouch mucosa by endoscopic and pathologic evaluations had evidence of extramucosal disease on MRI. Of these two, one patient had a large pelvic peripouch abscess, and the other had a small ischiorectal abscess, both of which were drained under CT guidance. The two remaining patients showed normal results according to MRI, endoscopic, and histopathologic criteria. Of the nine patients imaged, seven have a final diagnosis of Crohn s dis- AJR:187, October 2006 W387

Nadgir et al. Fig. 2 36-year-old woman with pouch.

(arrow). ease, while the remaining two continue to have a diagnosis of ulcerative colitis.

3 47-year-old man with pouch. Endoscopic image shows erythematous, friable, ulcerated pouch mucosa. Fig.

A, Gadolinium-enhanced T1 (spectral inversion recovery) axial image shows large, multiloculated collection (arrow)

3 Nadgir et al. Fig year-old woman with pouch. Gadolinium-enhanced T1 (spectral inversion recovery) axial image shows marked abnormal enhancement of pouch wall (arrow). ease, while the remaining two continue to have a diagnosis of ulcerative colitis. The final diagnosis of Crohn s disease was made by the patients gastroenterologist and surgeon using Fig year-old man with pouch. Endoscopic image shows erythematous, friable, ulcerated pouch mucosa. Fig year-old woman with pouch and pelvic pain. A, Gadolinium-enhanced T1 (spectral inversion recovery) axial image shows large, multiloculated collection (arrow) posterior to pouch. B, T2 sagittal image shows same large collection (arrow) posterior to pouch (arrowhead). Pouch wall itself was normal radiographically and endoscopically. A histologic and endoscopic criteria along with laboratory results and clinical course. B W388 AJR:187, October 2006

Fig. 5 36-year-old woman with pouch. Gadoliniumenhanced T1 (spectral inversion recovery) axial image shows marked peripheral rim enhancement around perineal fluid collection.

1) and abnormal enhancement in four patients (Fig. 2); in the fifth case, enhancement could not be assessed because IV contrast material was not administered.

Histologic examination in these patients also showed findings indicative of active inflammation including architectural distortion, ulceration, and active epitheliitis and cryptitis.

4 Fig year-old woman with pouch. Gadoliniumenhanced T1 (spectral inversion recovery) axial image shows marked peripheral rim enhancement around perineal fluid collection. A In the five patients shown to have abnormal pouch mucosa by endoscopy and histopathology, MRI examinations showed mural thickening in all five patients (Fig. 1) and abnormal enhancement in four patients (Fig. 2); in the fifth case, enhancement could not be assessed because IV contrast material was not administered. In these patients, thickening and enhancement by MRI correlated with erythematous, friable, and ulcerated mucosa at endoscopy (Fig. 3). Histologic examination in these patients also showed findings indicative of active inflammation including architectural distortion, ulceration, and active epitheliitis and cryptitis. Extramucosal disease activity was shown in all seven abnormal MRI examinations. Peripouch fluid collections were identified as T1 dark and T2 intermediate to bright collections with peripheral rim enhancement after contrast administration (Fig. 4). Fluid collections near the pouch or at the perineum were shown in five examinations (Fig. 5). These fluid collections ranged in size from 6 mm to 9 cm in the greatest dimension. Fig. 6 Sinus and fistula tracts in two patients. A, 30-year-old man with pouch. T1 axial image shows dark, curvilinear sinus tract (arrow) between pouch (white arrowhead) and peripouch fluid collection (black arrowhead). Fig. 7 B, 47-year-old man with pouch. Gadolinium-enhanced T1 (spectral inversion recovery) axial image shows marked enhancement of right perineal fistula (arrowhead), which extended to skin surface. B AJR:187, October 2006 W389

Nadgir et al. Fig. 8 36-year-old woman with pouch.

Fistulas and sinus tracts were identified on MRI in three studies in multiple imaging planes (Fig. 6).

T2 axial image shows extensive fatty proliferation around abnormal, thickened pouch wall.

5 Nadgir et al. Fig year-old woman with pouch. T2 axial image shows multiple peripouch lymph nodes (white arrow) adjacent to small fluid collection (arrowhead) posterior to abnormally thickened pouch (black arrow). Fistulas and sinus tracts were identified on MRI in three studies in multiple imaging planes (Fig. 6). All of these tracts originated at or near the pouch and were intimately associated with fluid collections. Fig year-old man with pouch. T2 axial image shows extensive fatty proliferation around abnormal, thickened pouch wall. No definitive criteria for peripouch lymphadenopathy in humans are described in the English-language literature. For the purposes of this investigation, we characterized lymphadenopathy as one lymph node greater than Fig year-old man with pouch. T1 axial image shows marked peripouch fat stranding (arrow) near abnormally thickened pouch (arrowhead). 1 cm in the greatest dimension or three or more peripouch lymph nodes. This was shown in all seven abnormal cases. The adenopathy was more pronounced in the more severe cases of pouchitis, with larger and more numerous peripouch lymph nodes (Fig. 7). The peripouch fat was evaluated for stranding and proliferation. Peripouch fat stranding was seen in all seven abnormal studies. As with adenopathy, the more severe cases of complicated pouchitis showed greater degrees of peripouch fat infiltration than the milder ones (Fig. 8). Fatty proliferation was shown by MRI in four examinations (Fig. 9). Strictures within or near the pouch were not definitely seen in any of the MRI examinations, whereas ileoileal stricturing was seen endoscopically in three patients, specifically at the site of anastomosis between the distal ileum and the ileal pouch. Discussion Pouchitis is a common problem seen in patients with ulcerative colitis who have undergone ileal pouch anal anastomosis. In a large published series [10], 40% of patients had a single episode of pouchitis, whereas 15% and 5% experienced intermittent episodes and chronic pouchitis, respectively. Although mild cases can be managed medically, the W390 AJR:187, October 2006

6 complicated cases require more aggressive treatment, closer surveillance, and numerous follow-up imaging examinations. IBD commonly presents at a young age, and patients with complicated courses often require repeated imaging studies such as barium examinations of the upper and lower alimentary tract or CT. Excessive exposure of patients to ionizing radiation is becoming a growing concern among radiologists and clinicians, especially for these young patients who tend to require multiple examinations. For these reasons, MRI is becoming an increasingly used imaging technique for patients with IBD, particularly for those with protracted or complicated courses. Although MRI has been shown to be highly useful in monitoring disease activity in patients with Crohn s disease and ulcerative colitis, little has been reported regarding the utility of MRI in postoperative evaluation of the pouch. In this study, we investigated the value of MRI in assessing the presence of mucosal and extramucosal disease activity within and around the pouch in symptomatic patients with clinically suspected complicated pouchitis who had undergone an ileal pouch anal anastomosis procedure for treatment of ulcerative colitis. In our series, MRI showed mural abnormalities in all of the symptomatic patients in whom mucosal disease was eventually confirmed with endoscopic and pathologic evaluation. Mucosal disease was manifested on MRI as pouch mural thickening (2 mm or greater thickness of pouch wall) and abnormal enhancement (enhancement greater than that of adjacent normal bowel loops). These findings correlated visually with pouch erythema, ulceration, and friability and histopathologically with active inflammation. MRI was particularly useful for identifying the extent and severity of extramural disease, such as peripouch fatty infiltration and proliferation, lymphadenopathy, peripouch fat stranding, associated fluid collections, and sinus tract and fistula formation. This additional information provided by MRI cannot always be obtained by endoscopy or barium examinations and may prove to be useful for patient management decisions. Another potentially important observation in this series is that the two pouches shown to be normal by MRI were also determined to be unremarkable on endoscopic and pathologic evaluation. This suggests that a negative MRI examination can potentially be a good negative predictor of pouch disease. However, this remains to be proven with a larger series of patients. Our MRI examinations did not show anastomotic stricturing, which was seen endoscopically in three patients. The abrupt caliber change because of anastomotic ileoileal stricture would likely be visible on MRI if the patients had received either oral or anal bowel preparation. In this series, none of the patients received a specific bowel preparation. However, because all patients with suspected pouchitis still undergo endoscopic evaluation and because strictures can be well visualized on endoscopy, this was not considered to be a severe limitation of the MRI examination. Limitations of our investigation include our small sample size of nine patients and the retrospective design. Although the MRI examinations correlated well with endoscopic and pathologic findings, a larger prospective series is necessary to more fully evaluate the utility of MRI in diagnosing complicated pouchitis. Gadolinium enhancement proved valuable in identifying mucosal disease, fistulas, and sinus tracts and in delineating abscesses. Unfortunately, two examinations were performed without contrast material. Ideally, all MRI examinations performed for suspected pouchitis should be performed with contrast material. Seven of the nine patients included in this series now have a final diagnosis of Crohn s disease. Although our sample size is small, this finding supports the notion that patients with clinically complicated pouchitis may ultimately be found to have Crohn s disease. Findings of fistulas, sinus tracts, and fatty proliferation are certainly more characteristic of Crohn s disease than of ulcerative colitis. In the setting of chronic or complicated pouchitis after ileal pouch anal anastomosis, these findings should raise the suspicion of possible misdiagnosis. The patients may need to undergo additional evaluation for Crohn s disease. Our initial results suggest that MRI should be considered in patients who present with complicated pouchitis and have undergone ileal pouch anal anastomosis. MRI offers the ability to show mural and extramural abnormalities, multiplanar capability, and reduced radiation exposure. Those advantages make MRI a comparable and possibly preferable imaging technique compared with CT or barium examinations. MRI can add to the endoscopic impression by showing findings of extramural disease activity, including peripouch stranding and fluid collections, fistulas and sinus tracts, and lymphadenopathy. MRI findings of complicated pouchitis should raise the suspicion of Crohn s disease and prompt further clinical investigation. References 1. Mahadevan U, Sandborn WJ. Diagnosis and management of pouchitis. Gastroenterology 2003; 124: Thoeni RF, Fell SC, Engelstad B, Schrock TB. Ileoanal pouches: comparison of CT, scintigraphy, and contrast enemas for diagnosing postsurgical complications. AJR 1990; 154: Alfisher MM, Scholz FJ, Roberts PL. Radiology of ileal pouch-anal anastomosis: normal findings, examination pitfalls, and complications. Radio- Graphics 1997; 17: Low RN, Francis IR, Politoske D, Bennet M. Crohn s disease evaluation: comparison of contrast-enhanced MR imaging and single-phase helical CT scanning. J Magn Reson Imaging 2000; 11: Low RN, Sebrechts CP, Politoske DA, Bennet MT, Flores S, Snyder RJ. Crohn disease with endoscopic correlation: single-shot fast spin-echo and gadolinium-enhanced fat-suppressed spoiled gradientecho MR imaging. Radiology 2002; 222: Koh DM, Miao Y, Chinn RJ, et al. MR imaging evaluation of the activity of Crohn s disease. AJR 2001; 177: Giovagnoni A, Misericordia M, Terilli F, Brunelli E, Contucci S, Bearzi I. MR imaging of ulcerative colitis. Abdom Imaging 1993; 18: Shoenut JP, Semelka RC, Magro CM, Silverman R, Yaffe CS, Micflikier AB. Comparison of magnetic resonance imaging and endoscopy in distinguishing type and severity of inflammatory bowel disease. J Clin Gastroenterol 1994; 19: Libicher M, Scharf J, Wunxch A, Stern J, Dux M, Kauffmann GW. MRI of pouch-related fistulas in ulcerative colitis after restorative proctocolectomy. J Comput Assist Tomogr 1998; 22: Sandborn J. Pouchitis following ileal pouch-anal anastomosis: definition, pathogenesis, and treatment. Gastroenterology 1994; 107: AJR:187, October 2006 W391

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