PURPOSE: The uncut Roux operation prevents the Roux stasis syndrome by preserving neuromuscular continuity between the proximal jejunum and the Roux limb, but this technique has an unacceptably high incidence of dehiscence of the staple lines with subsequent reflux gastritis or esophagitis. The authors designed a modified uncut procedure to avoid dehiscence of the staple lines. The aim of this study was to review whether this technique might be useful by examining the histologic change on animal study and the postoperative radiologic study of patients with modified uncut reconstruction. METHODS: Between February 1997 and December 2000, the UGI study was reviewed in 213 patients undergoing the modified uncut Roux reconstruction at Soonchunhyang University Hospital, Chunan, Korea, at 2 and 8 weeks after operation, to evaluate the incidence of dehiscence and the leakage of staple lines. Animal study included ten pigs, 5 underwent conventional uncut Roux procedure with staple, while the other 5 received reinforcing whole layer suture with black silk on the staple lines. The animals then underwent a second operation at 15 days after operation to evaluate histologic change and dehiscence of staple lines. RESULTS: Dehiscence and leakage were not found in any of the 213 patients undergoing modified uncut Roux reconstruction. In the animal study, 2 of 5 cases (40%) receiving conventional uncut Roux reconstruction had dehiscence, whereas dehiscence was absent in all 5 cases receiving modified uncut Roux reconstruction and these 5 animals showed more marked infiltration of inflammatory cells, vascular formation and more severe fibrosis on histologic examination. CONCLUSION: The conventional uncut Roux procedure suffer dehiscence of the staple lines with subsequent reflux gastritis or esophagitis. Therefore, modified uncut Roux reconstruction might prevent a jejunal leakage in the case of staple line dehiscence and might prevent dehiscence of staple lines.