Complex Procedures in Transanal Endoscopic Microsurgery: Intraperitoneal Entry, Ultra Large Rectal Tumors, High Lesions, and Resection in the Anal Canal.

Transanal endoscopic microsurgery (TEM) allows the local excision of rectal tumors and achieves lower morbidity and mortality rates than total mesorectal excision. TEM can treat lesions up to 18 to 20 cm from the anal verge, obtaining good oncological results in T1 stage cancers and preserving sphincter function. TEM is technically demanding. Large lesions (>5 cm), those with high risk of perforation into the peritoneal cavity, those in the upper rectum or the rectosigmoid junction, and those in the anal canal are specially challenging. Primary suture after peritoneal perforation during TEM is safe and it does not necessarily require the creation of a protective stoma. We recommend closing the wall defect in all cases to avoid the risk of inadvertent perforation. It is important to identify these complex lesions promptly to transfer them to reference centers. This article summarizes complex procedures in TEM.