PURPOSE Reconstruction following a total colectomy for ulcerative colitis (UC) offers patients the opportunity to avoid a permanent ileostomy. Ileal pouch-anal anastomosis (IPAA) is the gold standard, however ileorectal anastomosis (IRA) can be considered in select patients and may reduce infertility. The rates of IRA reconstruction and the outcomes following have not been reported in Australia. METHODOLOGY A retrospective data linkage study of the NSW population over a 19-year period. The primary outcome was IRA failure, defined as permanent ileostomy formation with or without proctectomy, or IPAA formation. The secondary outcome was the rate of malignant transformation in the retained rectum. Associations with patient demographic and hospital factors (including hospital IBD colectomy volume) were assessed. RESULTS IRA reconstruction was performed in 62/559 (11.1%) patients, and was more common in older, comorbid patients, for malignant indications, paediatric cohorts, in low colectomy volume, and outer regional hospitals (all P<0.05). Failure occurred in 25/62 after a mean follow up of 8.4 years(SD ±4.66), 5-year failure rate 39%(95%CI 25%-50%). Conversion to a pouch occurred in 25.8%(n=16), after a median 7.5 months(range 2.3-53.0). Two patients (3.2%) developed malignant transformation in the retained rectum requiring proctectomy after a mean of 9.9 years. CONCLUSION The rates of IRA failure (40.3%) and malignant rectal transformation (3.2%) in NSW are higher than what has been reported internationally, 20.4% and 2.4%, respectively. While IRA remains an option in select cohorts, patients need be counselled on the rates of failure, pouch conversion as well as the importance of ongoing endoscopic surveillance of the rectum.