The anorectum is the terminal portion of the gastrointestinal tract. It is embedded in the osseous pelvis and surrounded by urogenital organs as well as muscular, ligamentous, and connective tissue structures. It is the functional unit that maintains fecal continence by providing both a stopper-equipped reservoir and a controlled expulsion mechanism for feces. The rectum is the last and partially extraperitoneal segment of the large intestine. It starts at the rectosigmoid junction and continues through the pelvic floor into the anal canal. The nonmobilized rectum is characterized by three distinct endoluminal curves. The resulting folds that are seen on endoscopy are referred to as the valves of Houston. Definitions of where the sigmoid colon ends and the rectum begins include: (1) a distance of fifteen centimeters above the anal verge, (2) the position of the peritoneal reflection, and (3) the level of the sacral promontory. We maintain that the most useful landmark from a functional as well as surgical viewpoint is the confluence of the teniae coli at the rectosigmoid junction [
]. Because this anatomic reference point cannot be visualized endoscopically, the National Cancer Institute has recently defined the rectum as the last twelve centimeters above the anal verge for the purpose of uniformity in clinical trials [
- Stoss F.
Investigations of the muscular architecture of the rectosigmoid junction in humans.
Dis Colon Rectum. 1990; 33: 378-383
]. This definition is useful in preparing for a low anterior resection versus a sigmoid resection, particularly when measured with a rigid sigmoidoscope.
- Nelson H.
- Petrelli N.
- Carlin A.
- et al.
Guidelines 2000 for colon and rectal cancer surgery.
J Natl Cancer Inst. 2001; 93: 583-596
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