肠系膜下动脉系的解剖变异对直肠癌根治术具有重要的临床意义。左结肠动脉、结肠边缘动脉弓的解剖变异要求我们在处理肠系膜下动脉时，在彻底清扫肠系膜下动脉根部至左结肠动脉根部的中央组淋巴结的同时，保留左结肠动脉主干，这样既达到了根治的目的，又有利于控制手术风险，促进手术后恢复，减少吻合口瘘等术后并发症。对乙状结肠动脉、肠系膜下静脉的解剖变异的认识提示我们在术中时刻谨慎操作，防范意外出血等并发症。

The anatomic variation of the inferior mesenteric artery system has important clinical significance in rectal cancer radical operation.The variation required a thorough lymph nodes cleaning from the inferior mesenteric artery to the root of the left colic artery root of central group of lymph node and preservation of the left colonic artery at the same time when dealing with the inferior mesenteric artery.It will not only reach the target of radical left colic artery, but also control the risk of operation, promote recovery after operation, and reduce the postoperative complications such as anastomotic fistula et al.The understanding of the anatomic variation of the sigmoid colon and inferior mesenteric vein suggests the cautiousness in operation and prevent the complications such as accidental bleeding et al.