Ileal pouch and related complications: spectrum of imaging findings with emphasis on MRI.

Proctocolectomy with ileal pouch-anal anastomosis (IPAA) is the established surgical therapy for familial adenomatous polyposis (FAP) and refractory ulcerative colitis (UC). Despite general patient satisfaction with preserved fecal continence, this procedure is associated with a significant long-term morbidity approaching 70% after 10 years, and with a non-negligible rate of pouch failure leading to removal and permanent ileostomy. Following a concise description of the surgical technique, the normal imaging appearance of the ileal "pouch" reservoir at pelvic CT and MRI is explained. Since awareness of their imaging appearances is needed for a correct diagnosis, we discuss and illustrate common and unusual pouch-related complications, including pouchitis and irritable pouch disease; anastomotic leakages and pelvic abscess collections; fistulas involving the ano-perianal region, urinary bladder, vagina, perineal skin, and subcutaneous planes; anal stenosis and small-bowel obstruction. In our experience, pelvic contrast-enhanced MRI has proven invaluable for the diagnostic assessment of patients with suspected pouch-related complications, allowing differentiation of uncomplicated pouchitis from pelvic sepsis, the latter requiring aggressive therapy and possible even in patients with normal endoscopic findings.