DOI:10.2214/AJR.05.1019
AJR 2006; 187:W386-W391
© American Roentgen Ray Society
MRI of Complicated Pouchitis
Rohini N. Nadgir1,
Jorge A. Soto1,
Klea Dendrinos2,
Brian C. Lucey1,
James M. Becker3 and
Francis A. Farraye2
1 Department of Radiology, Boston University Medical Center, 88 E Newton St.,
2nd Floor, Boston, MA 02118.
2 Department of Gastroenterology, Boston University Medical Center, Boston, MA
02118.
3 Department of Surgery, Boston University Medical Center, Boston, MA
02118.
Received June 14, 2005;
accepted after revision August 30, 2005.
Address correspondence to J. A. Soto
(jorge.soto{at}bmc.org).
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Abstract
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.
Keywords: gastrointestinal radiology • inflammatory bowel disease • MRI • pelvic imaging
Introduction
Pouchitis is the most common complication of ileal pouch-anal 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 anastomosis 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.
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 disease,
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 histologic and endoscopic criteria along
with laboratory results and clinical course.
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Fig. 4B —42-year-old woman with pouch and pelvic pain. T2 sagittal
image shows same large collection (arrow) posterior to pouch
(arrowhead). Pouch wall itself was normal radiographically and
endoscopically.
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Fig. 6A —Sinus and fistula tracts in two patients. 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).
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Fig. 7B —Sinus and fistula tracts in two patients. 47-year-old man
with pouch. Gadolinium-enhanced T1 SPIR (spectral inversion recovery) axial
image shows marked enhancement of right perineal fistula (arrowhead),
which extended to skin surface.
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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 (Figs.
4A and
4B). 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.
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Fig. 8 —36-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).
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Fistulas and sinus tracts were identified on MRI in three studies in
multiple imaging planes (Fig.
6A). All of these tracts originated at or near the pouch and were
intimately associated with fluid collections.
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
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 (Figs. 7A and
7B).
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 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.
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Abstract
Introduction
