Rectal tumors are common in gastrointestinal surgery. Smaller benign tumors can be removed during fiberoptic enteroscopy. Larger, broad-based benign tumors and early malignant tumors require surgical intervention. Transabdominal, transsacral and transanal approaches are usually used. Either procedure, including the recent development of laparoscopic surgery, has systemic implications and is associated with higher treatment costs and complications. Local resection is attractive to patients and physicians because of the advantages of less surgical trauma, lower risk, and fewer postoperative complications. However, due to the special anatomical location of the rectum, local excision of rectal masses is technically difficult, and the indications for local excision, whether trans-sacral or transanal, are limited and the operation is difficult, traumatic, and has many complications. The emergence of transanal minimally invasive surgery (TEM) has largely compensated for the shortcomings of these procedures. Due to its microscopic magnification and long operating distance, it can perform local surgical operations in all parts of the rectum and even the lower sigmoid colon, and obtain the results of less trauma, faster recovery and precise operation. What is TEM? The so-called TEM (Transanal Endoscopic Microsurgery) is a minimally invasive anus-preserving surgical method to remove tumors through the anus. The procedure is performed with a special surgical system. This procedure was developed by German doctors Buess and Mentges from 1980 to 1983 and was first used in clinical practice in 1983. The system consists of a special proctoscope, special surgical instruments and a visualization system. Proctoscope diameter of 4cm, axis length of 12cm and 20cm, to adapt to different parts of the lesion, fixed to the operating table through the fixed device, proctoscope panel with four with a special rubber cuff closed operation hole, a variety of special endoscopic equipment, including tissue grasping forceps, scissors, straight and curved needle tip electrocoagulator, etc., through the operation hole for surgical operations, another channel for stereoscopic use and There is another channel for stereoscopic use and can be connected to the image monitoring system, low-pressure (15mmHg) CO2 continuous inflation dilates the rectum, so that the rectum and lesions are fully exposed to facilitate surgery. TEM is suitable for the treatment of adenomas, recurrent adenomas, low-risk rectal cancer (moderately differentiated to well-differentiated stage T1 lesions without lymphatic or neurological infiltration), fistulas and post-anastomotic rectal strictures with a wide base 4-20 cm from the anal verge or without a tip. It is also an appropriate treatment for certain stage T2 and T3 rectal cancers with specific indications, such as palliative surgery for elderly or high-risk patients who are unwilling or unable to tolerate transabdominal radical surgery and local control for patients with extensive metastases. Other benign tumors of the rectum (lipomas, smooth muscle tumors, etc.) or perirectal benign tumors and the diagnosis or biopsy of rectal bleeding are also indications. Lesions too close to the anal verge (2-4 cm) are not suitable for TEM because they are not conducive to instrument placement and prone to air leakage, and lesions should not be too high, otherwise they are difficult to reach and difficult to expose, generally within 20 cm from the anus. The maximum diameter of the lesion should be less than 1/3 to 1/2 of the rectal circumference to avoid excessive tension after suturing causing wound dehiscence or postoperative rectal stenosis. For larger polyps and adenocarcinomas that require total rectal wall resection, only lesions in obvious extraperitoneal parts of the rectum should be selected to avoid penetration into the abdominal cavity. For tumors in the middle and upper rectum and extraperitoneal parts of the rectum, only mucosal resection should be performed. The location of rectal peritoneum is 20 cm from the anal verge in the posterior wall of rectum, 15 cm from the anal verge in the lateral wall, and 12 cm from the anal verge in the anterior wall, so adenocarcinoma in the anterior wall of rectum, higher than 12 cm, cannot be performed TEM. for posterior wall tumor, part of posterior rectal fat can be resected together. For anterior wall and lateral wall tumors, we should be careful not to damage the vagina and ureter.