Background Anastomotic leakage is a major complication after anterior resection for rectal cancer. The double-stapling technique (DST) is the main method for creating a colorectal anastomosis. However, the rate of anastomotic leakage after DST remains high, and the technical risk factors have not been well established. Materials and methods Five methods of colorectal anastomosis were performed on the porcine rectum and colon: single-stapled double-purse-string (SSDP), DST, side-to-side with a linear stapler (SS-L), side-to-side with a circular stapler (SS-C), and SS-C with hand-sewn reinforcement (n = 6 for each method). In each group, burst pressures were tested, paying special attention to the locations of the first disruptions. The anastomosis line, including staples, was embedded in polyester resin, and polished sections were examined histologically. Results Burst pressures were significantly higher in the SS-L and SS-C than those in the SSDP and DST groups (P < 0.001) and were higher in the SS-C with hand-sewn reinforcement than those in the SS-L and SS-C groups (P < 0.001). Remarkably, in the SSDP, DST, and SS-C groups, the first disruptions occurred on the staple line created by the circular stapler. Conclusions The experimentally strongest colorectal anastomosis created with instruments currently in use was a SS-C. This anastomosis does not overlap staple lines and does not require a purse-string suture. Hand-sewn reinforcement was effective in increasing the anastomotic strength.
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