The success of laparoscopic cholecystectomy has stimulated interest in other general surgical procedures, namely Nissen fundoplication, inguinal hernia repair, splenectomy, adrenalectomy, and colon resection. Indeed, there has been an explosion of clinical and basic science research in this regard. The surgery is labeled minimally invasive surgery, but this term is actually a misnomer because surgery by any means is invasive and the techniques used are generally extensions of their open counterparts. Instead, these procedures should be looked upon as being “minimal-access operations” owing to the fact that they are performed through smaller, much more limited portals of entry. Transanal endoscopic microsurgery (TEM) is also a minimal-access procedure, and it follows the same principles and indications as conventional transanal surgery, but the similarity ends there. TEM extends the boundaries of transanal surgery by providing access to lesions that were previously inaccessible by pre-existing means and does so with improved instrumentation and visibility. The net result is an operative approach to rectal pathology that might have otherwise required a transsacral dissection or laparotomy and low anterior resection; morbidity, length of stay, and discomfort are therefore potentially lessened.

TEM distinguishes itself from other endoscopic and minimal-access procedures in several ways. First, the visual image is obtained through a binocular stereoscopic eyepiece, which provides a depth of field quite different from that obtained with monocular instruments or video cameras. Second, the instruments are inserted and manipulated in parallel planes, in contrast to laparoscopic surgery, where opposing portals are used to achieve the traction and countertraction needed to expose the plane of dissection. As a result, exposure can be difficult to obtain, and for the novice, this can be a frustrating endeavor. Lastly, the conditions treated with TEM—adenomas, selected cancers, and prolapse— are encountered far less frequently than those treated laparoscopically. Consequently, as a result of this infrequency, combined with the considerable skill required and the high cost of the equipment, TEM will become the domain of only a few surgeons.