Transanal endoscopic microsurgery: current indications and techniques.

Transanal endoscopic microsurgery (TEM) was introduced in 1984 as a direct-imaging alternative to traditional treatments of rectal cancer. Traditional treatments have ranged from the low-morbidity (but difficult) transanal excision to the permanent morbidity of an abdominal perineal resection. The ability to perform full-thickness excisions with magnification, good illumination, and the increased exposure afforded by insufflation and long instruments has dramatically increased the indications for and efficacy of transanal excisions of malignant and premalignant lesions. T h e ins t rument set includes a 4 cm diameter operating rectoscope with either a 12 or 22 cm long barrel. Ins t rumenta t ion replicates the tools of the advanced laparoscopic surgeon and includes graspers, cautery, scissors, needle holders, and a suction device. Highreso lu t ion imaging is obtained ei ther with the originally described stereoscopic optics, which suffer from requiring the ergonomic disaster of an immobile, bent-over position, or by the use of an adaptor that permits a standard 25-degree laparoscope and camera system to be used. This permits a heads-up view of the projected image on video screens, which are accessible to the entire operating room team. T h e primary advantage of T E M is the ability to accurately determine margins and execute wide, full-thickness excisions under high magnification. Equally important is the ability to execute formal, non-nar rowing, transverse closures of a fullthickness defect. Closure of the full-thickness excision site is even more technically demanding than standard laparoscopic suturing, but does allow accurate repair of even large defects including those after in t raper i toneal full-thickness excision. T E M has permitted some investigators to perform primary reanastomosis fol lowing endoscopical ly per formed sleeve resections. Current indications for T E M include the following: • Adenomatous and villous polyps, which are unresectable endoscopically • Stage I and II cancers (with adjuvant therapy) • Simple prolapse • Rectal ulcers and other benign lesions that require wide excision Operative success is high with these excisions and conversions to open procedures are rare, in most series less than 1%. Cumulative experience in the literature now totals more than 1000 procedures and documents an average length of stay of less than 48 hours and an average perioperative complication rate of 5 %. Postoperative pain is uncommon and the main complications reported are infection (2.5%), dehiscence of the incisions (0% to 5%), and bleeding (5% to 10%). Recurrence rates following benign tumor excision are between 1% and 8%, which is much lower than the rates reported for standard transanal excisions. The role of T E M in the treatment of rectal cancer is not fully defined. Advocates cite the improved ability of imaging studies to accurately stage rectal cancers and the efficacy of modern chemoradiation protocols to justify this less invasive surgical approach. The reported actuarial 5-year cure rate for T1 cancers after T E M is 90%, which is comparable to more radical excisions. The local/regional recurrence rate for T3 lesions, however, approaches 65%, which underscores the importance of accurate staging of these patients to allow selection of those who will uady benefit. Cur ren t protocols rely on C T scans and endorectal ultrasound to determine the stage. Therefore T E M for cancer is subject to the accuracy limitations of these tests. Future developments such as positron emission tomographic scanning and radioimmunoguided imaging may allow selection of rectal cancer patients who would achieve optimal results from image-guided full-thickness T E M resection.