BACKGROUND: In inflammatory bowel disease (IBD), many scenarios call for fecal diversion, leaving behind defunctionalized bowel. The theoretical risk of colorectal cancer (CRC) in this segment is frequently cited as a reason for resection. To date, no studies have characterized the incidence of neoplasia in the diverted colorectal segments of IBD patients. METHODS: A retrospective cohort analysis was conducted for IBD patients identified through a tertiary care center pathology database. Patients that had undergone colorectal diversion and were diverted for ≥ 1 year were included. Incidence of diverted dysplasia/CRC was calculated for Crohns disease (CD) and ulcerative colitis (UC) with respect to diverted patient-years (dpy) and patient-years of disease (pyd). RESULTS: In total, 154 patients comprising 754 dpy and 1984 pyd were analyzed. Only 2 cases of diverted colorectal dysplasia (CD 1, UC 1) and 1 case of diverted CRC (UC) were observed. In the UC cohort (n = 75), the rate of diversion-associated CRC was 4.5 cases/1000 dpy (95% CI 0.11-25/1000) or 1.5 cases/1000 pyd (95% CI 0.04-8.2/1000). In the CD cohort (n = 79), no patients developed CRC, although a dysplasia rate of 1.9 cases/1000 dpy (95% CI 0.05-11/1000) or 0.77 cases/1000 pyd (95% CI 0.02-4.3/1000) was observed. All patients developing neoplasia had disease duration > 10 years and microscopic inflammation. CONCLUSIONS: Diverted dysplasia occurred infrequently with rates overlapping those reported in registries for IBD-based rectal cancers. Neoplasia was undetected in patients with < 10 pyd, regardless of diversion duration, suggesting low yield for endoscopic surveillance before this time.