Determinants of optimal bowel function in ileal pouch-anal anastomosis - physiological differences contributing to pouch function

Background: Variability in functional outcome after ileal-pouch anal anastomosis (IPAA) is to a large extent unexplained. The aim of this study was to perform multiple physiological and biochemical tests including an endoscopic examination with histology on IPAA patients with well and poorly functioning pouches to determine factors, or combinations thereof, contributing to functional outcome.Methods: All patients with ulcerative colitis undergoing restorative proctocolectomy between 2000 and 2013 (N=108) were interviewed using a pouch functioning score. The best and worst functioning quartiles were invited to undergo examination with a barostat measuring pouch volume at preset variable distension pressures, and a pouch endoscopy.Results: Forty five of 58 eligible patients agreed to participate. The most significant physiological parameter differing between the well and poorly functioning pouches was pouch volume at first sensation, urge and discomfort (p value <.001). Urge volumes were 213 (CI 171-256) ml for poorly and 352 (CI 305-401) ml for well functioning pouches. Pouchitis episodes were negatively correlated to function. The poorly functioning patients had a higher prevalence of histological signs of inflammation and hand-sewn anastomosis, and a longer remaining rectal cuff, however, nonsignificant. The pouch pressure at sensation thresholds did not differ between the groups.Conclusions: Pouch volume is the most dominant predictor of pouch function in this study. The present comprehensive study of a multitude of different factors that possibly could be contributing to functional outcome, failed to shed much further light on the functional variability among pouch patients. The pouch physiology remains to a large extent unexplained.