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Resection principles: The mesenteric clearance technique dictates the extent of resection and is determined by the nature of the primary pathology, the intent of resection, the location of the lesion, and the condition of the mesentery.
Function after resection: Bowel function is often compromised after colorectal resection, especially after low anterior resection. For this reason, it is important to obtain a history of prior anorectal trauma and/or incontinence before considering a low anastomosis.
Ostomies: Preoperative marking for a planned stoma is critical for a patient’s quality of life. Ideally, a stoma should be located within the rectus muscle, in a location where the patient can easily see and manipulate the appliance, and away from previous scars, bony prominences, or abdominal creases.
Inflammatory bowel disease: Both Crohn’s disease and ulcerative colitis are associated with an increased risk of colorectal carcinoma. Risk depends on the amount of colon involved and the duration of disease.
Pathogenesis of colorectal cancer: A variety of mutations have been identified in colorectal cancer. Mutations may cause activation of oncogenes (K-ras) and/or inactivation of tumor suppressor genes (adenomatous polyposis coli [APC], deleted in colorectal carcinoma [DCC], p53).
Minimally invasive resection: Laparoscopy and HAL have been shown to be both safe and efficacious for colorectal resection.
Anal epidermoid carcinoma: Unlike rectal adenocarcinoma, anal epidermoid carcinoma is treated primarily with chemoradiation. Surgery is reserved for patients with persistent or recurrent disease.
Rectal prolapse: Rectal prolapse occurs most commonly in elderly women. Transabdominal repair (rectopexy with or without resection) offers more durability than perineal proctosigmoidectomy, but carries greater operative risk.
Hemorrhoids: Hemorrhoids are cushions of submucosal tissue containing venules, arterioles, and smooth muscle fiber. They are thought to play a role in maintaining continence. Resection is only indicated for refractory symptoms.
Fistula in ano: Treatment of fistula in ano depends on the location of the fistula, amount of anal sphincter involved in the fistula, and the underlying disease process.
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EMBRYOLOGY AND ANATOMY
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The embryonic gastrointestinal tract begins developing during the fourth week of gestation. The primitive gut is derived from the endoderm and divided into three segments: foregut, midgut, and hindgut. Both midgut and hindgut contribute to the colon, rectum, and anus.
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The midgut develops into the small intestine, ascending colon, and proximal transverse colon, and receives blood supply from the superior mesenteric artery. During the sixth week of gestation, the midgut herniates out of the abdominal cavity, and then rotates 270° counterclockwise around the superior mesenteric artery to return to its final position inside the abdominal cavity during the tenth week of gestation. The hindgut develops into the distal transverse colon, descending colon, rectum, and proximal anus, all of which receive their blood supply from the inferior mesenteric artery. During the sixth week of gestation, the distal-most end of the hindgut, the cloaca, is divided by ...