Incidence of new-onset benign anal disorders after bariatric surgery.

New-onset benign anal disorders (NBADs) represent a potential complication following bariatric surgery, although their incidence in this population is not well studied. The preoperative characteristics, weight loss, bowel habits and NBADs data of 196 patients with bariatric surgery were collected by telephone interviews and medical records review and evaluated retrospectively. Ninety-nine patients had undergone gastric bypass (GBP) and 97 had a modified biliopancreatic diversion (MBPD). Fifty-nine patients were excluded. The mean follow-up of the remaining 137 patients was 87.8 months, and 51 of them (37.2%) developed NBADs. Haemorrhoids were the most common diagnosis and 27.5% of the patients that developed NBADs were treated surgically. Patients who developed NBADs had a longer follow-up time (92.5 vs. 85.1 months, P = 0.003), and those with an abnormal bowel habit (diarrhoea or constipation) had a higher percentage of NBADs (54.5 vs. 28.3%, P = 0.003). NBADs were more frequent after MBPD (52.9%) than after GBP (21.7%) (P < 0.001). Multivariate analysis found that only an abnormal bowel habit was associated with NBADs, with an odds ratio of 3.2 (95% CI: 1.5-6.9, P = 0.003). As NBADs are a common complication after bariatric surgery, further studies should be performed to find the reasons for these complications.