LAUSR

Idiopathic pouchitis is the most common complication of ileal pouch–anal anastomosis, affecting up to 50–60% of ulcerative colitis pouch patients and 15–22% of familial adenomatous polyposis pouch patients 10 years after stoma closure [1,2]. Pouchitis can be clinically classified into three phenotypes: acute antibiotic-responsive (<4 episodes a year), chronic antibiotic-dependent ( � 4 antibiotic-responsive episodes or need for ongoing antibiotics), and chronic antibiotic-refractory pouchitis (CARP)[3]. Secondary causes of pouchitis include infections (Cytomegalovirus [CMV] and Clostridioides difficile), ischemia (asymmetric pouchitis), and nonsteroidal antiinflammatory drugs (NSAIDs)-associated pouchitis. Second, in patients who have never had a normal pouch function, idiopathic pouchitis needs to be distinguished from a chronic leak or sinus. Thirdly, other inflammatory complications of the pouch such as cuffitis and prepouch ileitis, non-inflammatory complications of the pouch, such as irritable pouch syndrome, can present similarly and need to be ruled out. While most acute episodes of pouchitis respond readily to a finite course of a single antibiotic, up to 20% can be refractory and more challenging to treat. A useful stepwise approach in such patients includes three steps: (i) ensuring this is an episode of acute idiopathic pouchitis, (ii) following an evidence-base selection of alternative or combination antibiotics, and (iii) accurate subtyping of antibiotic refractory pouchitis to allow for a targeted and personalized approach. Pouch symptoms of increased frequency, urgency and abdominal cramps are not specific to idiopathic pouchitis and can be seen in secondary pouchitis and noninflammatory pouch complications. Therefore, objective evaluation with pouchoscopy is needed. This is particularly crucial when managing a first episode of pouch dysfunction or when an empiric course of antibiotic fails. In fact, pouchoscopy is considered more cost-effective than an empiric trial of antibiotics for episodes of acute pouchitis [4]. It will help diagnose isolated cuffitis, prepouch ileitis and ischemic pouchitis (asymmetric sharply demarcated inflammation within the pouch body). Furthermore, the degree of pouch body inflammation on pouchoscopy can help distinguish pouchitis from irritable pouch syndrome. Using the Pouchitis Disease Activity Index (PDAI), which consists of symptom (0–6 points), endoscopy (0–6 points), and histology (0–6 points) sub-scores, a PDAI score of ≥7 points is diagnostic for pouchitis [5]. Second, while the PDAI allows diagnosis of pouchitis, it does not distinguish idiopathic pouchitis from secondary causes of pouchitis or other causes of diarrhea such as celiac disease. Hence, this approach should be coupled with a fecal sample tested for C. difficile toxin, a review of NSAID intake and celiac serology. Importantly, special attention should be made to the onset of pouch symptoms in relation to stoma closure. Those whose symptoms started immediately after stoma closure should be suspected of and investigated for a pouch leak or sinus. Third, and particularly in patients with antibiotic refractory pouchitis, Crohn’s-like disease of the pouch (CLDP) needs to be ruled out. In the absence of defining Crohn’s-like features, such as complex peri-pouch fistulas or proximal small bowel strictures, the distinction may be difficult. This is particularly true since granulomas are only seen in 12–13% of CLDP cases. A diagnosis of CLDP is suggested by the presence of deep ulcerations in the pouch body combined with risk factors for CD such as a preoperative diagnosis of indeterminate colitis, active smoking, and positive anti-Saccharomyces cerevisiae antibodies (ASCA).