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Original Research |
1 Department of Radiology, Hospital of the University of Pennsylvania, 3400
Spruce St., Philadelphia, PA 19104.
2 Department of Surgery, Hospital of the University of Pennsylvania,
Philadelphia, PA 19104.
Received October 17, 2006;
accepted after revision January 26, 2007.
M. S. Levine and S. E. Rubesin are consultants for E-Z-EM, Inc.
Abstract
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MATERIALS AND METHODS. Our radiology database revealed 42 patients with contrast enemas after total proctocolectomy and ileal pouch–anal anastomosis who fulfilled our exclusion criteria. The initial postoperative contrast enemas were reviewed blindly to determine the diameter of the ileoanal anastomosis. The diagnosis of a stricture was made only if the patient had signs of intestinal obstruction after ileostomy closure with confirmation on follow-up contrast enema or sigmoidoscopy and clinical improvement after anastomotic dilatation. The data were then correlated to determine if there was a critical anastomotic caliber at or below which such strictures were likely to develop. Using this threshold value, the sensitivity and specificity of routine contrast enemas for detecting clinically relevant anastomotic strictures were then determined.
RESULTS. Six (14%) of the 42 patients who underwent total proctocolectomy and ileal pouch–anal anastomosis had strictures at the ileoanal anastomosis on contrast enemas. The mean diameter of the anastomosis was 5.8 mm in the six patients with anastomotic strictures versus 15 mm in the 36 patients without strictures (p = 0.0002). If an anastomotic diameter of 8 mm is defined as the critical caliber at or below which clinically relevant strictures are present, the sensitivity of contrast enemas for detecting strictures at the ileoanal anastomosis was 100% (six of six patients) and the specificity was 92% (33 of 36 patients).
CONCLUSION. Routine contrast enema after total proctocolectomy and ileal pouch–anal anastomosis is a sensitive test for detecting clinically relevant strictures at the ileoanal anastomosis when an anastomotic diameter of 8 mm or less is used as the threshold value for diagnosing these strictures. Such patients may need dilatation procedures to decrease the risk of anastomotic obstruction after ileostomy closure.
Keywords: abdomen • anastomotic strictures • barium enema • fluoroscopy • gastrointestinal radiology • ileal pouch–anal anastomosis • proctocolectomy • small bowel
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Total proctocolectomy and ileal pouch–anal anastomosis may be associated with a variety of early and late complications, including anastomotic leaks, pelvic abscesses, fistulas, pouchitis, strictures, and small-bowel obstruction [4–7]. Previous studies have shown that contrast enema examinations are useful for detecting many of these complications before takedown of the diverting ileostomy, particularly asymptomatic leaks from the ileal pouch or ileoanal anastomosis [8–12]. These contrast enemas are more readily performed as retrograde studies via the anus than as antegrade studies via the distal limb of the diverting loop ileostomy [13, 14].
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The remaining 42 patients composed our study group. The mean age of the patients was 44 years (age range, 20–68 years). Twenty patients (48%) were men and 22 (52%) were women. Thirty-eight patients (90%) underwent surgery for ulcerative colitis and four (10%) for familial adenomatous polyposis syndrome.
Contrast Enema Examinations
The 42 patients in our study group had a total of 51 contrast enema
examinations (nine patients also had examinations after ileostomy closure).
The studies were performed by retrograde administration of a water-soluble
contrast agent (Gastroview [diatrizoate meglumine and diatrizoate sodium],
Mallinckrodt; Hypaque [diatrizoate sodium], Nycomed) via a 22-French Foley
catheter inserted through the anus into the anal canal, ileal pouch, or both
at various times during the examination (depending on the preferences of the
examiner). Using digital fluoroscopic equipment (Diagnost 76, Philips Medical
Systems; Sireskop SD, Siemens Medical Solutions), spot images of the anal
canal, ileoanal anastomosis, and ileal pouch were routinely obtained with the
patient in lateral, frontal, and oblique positions (Figs.
1A,
1B, and
1C). All of the studies were
performed by residents, fellows, or one of three attending gastrointestinal
radiologists, and all were interpreted by one of the attending
radiologists.
Study Design
Medical and surgical records from these 42 patients were reviewed to
determine whether the patients had clinical signs or symptoms of intestinal
obstruction (including constipation, small-caliber stools, nausea or vomiting,
tenesmus, and pelvic pain) after takedown of the diverting ileostomy, whether
the patients with obstructive symptoms after ileostomy closure underwent
sigmoidoscopic examinations that revealed narrowing at the ileoanal
anastomosis, and whether subsequent digital or endoscopic balloon dilatation
of the anastomosis resulted in clinical improvement.
The initial postoperative contrast enema examinations in these 42 patients were reviewed in consensus by two of the authors (both experienced gastrointestinal radiologists) who were blinded to clinical presentation, treatment, and patient course. The studies were evaluated to determine the diameter and length of the ileoanal anastomosis (magnification was accounted for on the radiographs by using the known diameter of the 22-French Foley catheter as a reference standard on the images). Nine repeat contrast enema examinations after ileostomy closure were also reviewed for radiographic signs of obstruction at the ileoanal anastomosis, including pouch dilatation, delayed emptying of the pouch (this one parameter was assessed by reviewing the original radiology reports), excessive debris in the pouch, and small-bowel dilatation proximal to the pouch.
The diagnosis of a clinically relevant stricture at the ileoanal anastomosis was made only if the patient had signs or symptoms of intestinal obstruction after ileostomy closure, with confirmation of the stricture either on a repeat contrast enema examination showing radiographic signs of anastomotic obstruction (as previously discussed) or on follow-up sigmoidoscopy showing narrowing at the ileoanal anastomosis and subsequent clinical improvement after digital or endoscopic balloon dilatation of the anastomosis.
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The mean diameter of the ileoanal anastomosis was 5.8 mm (range, 4–8 mm) in the six patients with clinically relevant anastomotic strictures versus a mean diameter of 15 mm (range, 5–30 mm) in the 36 patients without strictures. The mean anastomotic diameter in the six patients with strictures was significantly smaller than that in the 36 patients without strictures (p = 0.0002). If an anastomotic diameter of 8 mm is defined as the critical caliber at or below which clinically relevant strictures are thought to be present, the sensitivity of routine contrast enema examinations for detecting such strictures at the ileoanal anastomosis before ileostomy closure was 100% (six of six patients) (Figs. 2A, 2B, 3A, and 3B) and the specificity was 92% (33 of 36 patients), with three false-positive studies for strictures (Figs. 4A and 4B).
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The contrast enema examinations were performed with the catheter tip in the anal canal in five (83%) of the six patients with strictures at the ileoanal anastomosis and in both the anal canal and ileal pouch in one (17%). Thus, no patients with anastomotic strictures had examinations performed with the catheter tip solely in the ileal pouch. In contrast, the contrast enema examinations were performed with the catheter tip in the anal canal in 18 (50%) of the 36 patients without anastomotic strictures, in the ileal pouch in 16 (44%), and in both the anal canal and ileal pouch in two (6%).
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In our study, the prevalence of strictures at the ileoanal anastomosis after total proctocolectomy and ileal pouch–anal anastomosis was 14%. In other studies, the prevalence of strictures has ranged from 8% to 14% [5–7, 15, 16]. To our knowledge, however, no previous studies have shown the utility of routine contrast enema examinations for detecting clinically relevant anastomotic strictures before ileostomy closure. In our study, the mean diameter of the ileoanal anastomosis in the six patients with strictures was 5.8 mm versus a mean diameter of 15 mm in the 36 patients without strictures. In one previous study, the mean anastomotic diameter in patients without clinical signs of strictures after ileal pouch–anal anastomosis also was 15 mm [10]. Unlike the earlier study, however, the mean diameter of the ileoanal anastomosis in our six patients with anastomotic strictures was significantly smaller than that in the 36 patients without strictures (p = 0.0002).
More important, when an anastomotic diameter of 8 mm was used as the critical caliber at or below which anastomotic obstruction was likely to develop after ileostomy closure, our sensitivity for detecting clinically relevant strictures at the ileoanal anastomosis was 100% (six of six patients) (Figs. 2A, 2B, 3A, and 3B) and our specificity was 92% (33 of 36 patients). Although our threshold value of 8 mm resulted in three false-positive examinations for strictures (Figs. 4A and 4B), there were no false-negatives because all symptomatic patients with strictures had anastomotic diameters of 8 mm or less.
Endoscopic balloon dilatation procedures for strictures at the ileoanal anastomosis are generally safe, effective, and well tolerated [17], whereas anastomotic obstruction after ileostomy closure is associated with substantial patient morbidity. Our ability to detect clinically relevant strictures at the ileoanal anastomosis with high sensitivity therefore has important implications for patient management because it could decrease the risk of intestinal obstruction after takedown of the diverting ileostomy by identifying those patients who are more likely to benefit from a dilatation procedure at or before ileostomy closure.
Some authors advocate digital rectal examination rather than contrast enema for detecting anastomotic strictures before ileostomy closure because of the accessibility of the anastomosis to the examiner's finger and the ease of performing this examination [14, 15]. Digital rectal examination is a relatively subjective test of stricture formation, however, and depending on the size of the examiner's finger, the critical anastomotic caliber below which obstruction is considered likely after ileostomy closure may vary. In contrast, our experience suggests that the contrast enema examination is a more objective and reliable test for detecting strictures at the ileoanal anastomosis when a fixed threshold diameter is used.
All six patients with anastomotic strictures on contrast enema examinations had their studies performed with the catheter tip in the anal canal (one patient had the catheter tip in the anal canal and ileal pouch at various times during the procedure), whereas 16 (44%) of the 36 patients without strictures had their studies performed with the catheter tip in the ileal pouch. It therefore is tempting to suggest that strictures are more likely to be detected at the ileoanal anastomosis when the catheter is positioned with its tip in the anal canal at or near the site of anastomotic narrowing. On the other hand, these findings may reflect a bias for performing the examination with the catheter tip in the anal canal in patients with anastomotic strictures in whom it is more difficult to advance the catheter into the ileal pouch. A controlled prospective study is needed to determine optimal placement of the catheter tip for these examinations.
Our investigation has the inherent limitations of a retrospective study, including selection bias and interpretation bias. Our analysis is also limited by the need to define clinically relevant strictures at the ileoanal anastomosis on the basis of subjective signs and symptoms of anastomotic obstruction after takedown of the diverting ileostomy because there is no uniform gold standard for the diagnosis of such strictures. The lack of repeat contrast enema examinations after ileostomy closure in many patients is another weakness of our study.
In conclusion, our experience suggests that routine contrast enema examination after total proctocolectomy and ileal pouch–anal anastomosis is a sensitive test for detecting clinically relevant strictures at the ileoanal anastomosis when an anastomotic diameter of 8 mm or less is used as the threshold value for diagnosing these strictures. Such patients may need dilatation procedures to widen the anastomosis and decrease the risk of anastomotic obstruction after ileostomy closure.
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