Correlation between serum serotonin and endoscopy inflammation scores in patients with ileal pouches.

Background: Inflammatory and functional complications are common in patients with inflammatory bowel disease (IBD) after restorative proctocolectomy with ileal pouch-anal anastomosis (IPAA). The pathogenesis of these complications remains poorly understood, and there is discrepancy between the clinical symptoms and objective endoscopic inflammation scores in these patients. While serum serotonin level has been reported to be associated with symptoms of irritable bowel syndrome, its association with ileal pouch disorders has not been studied.

Aim: To investigate the association between serum serotonin level and symptoms and endoscopic inflammation in patients with IPAA.

Methods: A total of 185 consecutive eligible IPAA patients who presented to a specialized Pouchitis Clinic from Jan 2009 to May 2009 were prospectively recruited. Patients were divided into 4 groups: normal pouch, irritable pouch syndrome (IPS), inflammatory pouch disorders (Crohn's disease, acute and chronic pouchitis, and cuffitis), and surgical complications. Serum serotonin level was measured and analyzed for correlation with clinical and endoscopic inflammation scores.

Results: Demographic and clinical variables were evaluated, including age, gender, smoking history, duration of UC, duration of the pouch, and disease category of the pouch. The median fasting serum serotonin level was comparable among the 4 groups: 94.0 ng/ml (interquartile range [IQR], 70.0, 128.1), 89.2 ng/ml (IQR 54.2, 155.9), 90.3 ng/ml (IQR 49.7, 164.1), 77.9 ng/ml (IQR 54.7, 129.0), for normal pouch, irritable pouch, inflammatory pouch disorders, and surgical complication groups, respectively (p=0.91). A significant association between serum serotonin level and the Pouchitis Disease Activity Index (PDAI) endoscopy subscore of the pouch (odds ratio [OR]=1.9, 95% confidence interval [CI]: 1.2, 2.9, p<0.05) and total PDAI endoscopy score (OR=1.8; 95% CI: 1.2, 2.8, p<0.05) in the inflammatory complication group were noted.

Conclusions: Serum serotonin level appears to correlate with the PDAI endoscopy subscores and total PDAI score in patients with inflammatory complications suggesting that the hormone may be involved in mechanisms of mucosal inflammation. These findings may promote future treatment strategies for patients with pouch inflammation.