Background: The gold standard of the management of rectal cancer in the middle and lower parts is low anterior resection with coloanal anastomosis. About 50% of the patients undergoing this procedure might experience some complications because of the low capacity of the neorectum. The aim of this study was to evaluate ileal J-pouch interposition as a neorectum between the anal canal and the remaining colon in comparison to coloanal anastomosis and transverse coloplasty. Methods: Twelve dogs, weighing 23-27 kg, were divided into three groups. After laparotomy, the volume of the primary rectum was measured so that it could be compared with that of the neorectum at the end of the study. After rectal resection in Group A, the colon was directly anastomosed to the anus. In Group B, a 5-cm longitudinal incision was made 2 cm proximal to the anastomosis and was sutured transversely (coloplasty). In Group C, a 5-cm ileal J-pouch was interposed between the colon and anus. After 8 weeks, the neorectum was evaluated for volume, radiology, and pathology.Results: All the samples were alive until the end of the study. The healing of the anastomotic lines was acceptable (pathologically) in all. The mean volume expansion was 20.9% in Group A, 21.7% in Group B, and 118.2% in Group C, with the latter being significantly higher than that of the other groups (P=0.03). Colon J-pouch and coloplasty after proctectomy in some situations have not been performable. This study evaluated the performance of ileal J-pouch interposition. Conclusion: This study showed that ileal J-pouch interposition might produce an acceptable reservoir function and that it seems feasible and safe in selected cases.