Surgery for Rectal Carcinoma (page 1 of 4)
By David S. Medich, M.D.
Director, Division of Colon and Rectal Surgery

Colon and rectal carcinoma arise from the mucosa (the innermost layer) and typically grow into the deeper layers of the bowel wall in a somewhat predictable manner. Once the tumor has reached the submucosa, it comes in contact with lymphatic and blood vessels and is capable of spreading to the draining lymphatic bed located along the blood vessels and then spreading via liver circulation. This occurs with greater frequency as the tumor penetrates through the layers of the bowel wall from the submucosa to the serosa (outermost layer) or beyond. In keeping with this known pathophysiology, the goal of surgery for colon and rectal carcinoma is to remove the tumor-bearing portion of bowel in one block with its lymph nodes and blood supply, and then restore intestinal continuity and function.

Theoretically, local control of the tumor is accomplished and the surgery is considered “curative” when all surgical margins are clear and there is no measurable systemic tumor. Therefore, the degree to which the tumor is locally controlled is a measure of the effectiveness of surgical therapy. This is accomplished more readily when the tumor arises from the colon or the intraperitoneal portion of the rectum (proximal third) as the mesentery is accessible and all radial margins are soft tissue that can be exposed and more safely dissected. Colon cancer recurrence after curative surgery is nearly always a systemic problem, and only in unusual circumstances is local recurrence (LR) a clinical problem. Carcinoma arising from the mid/distal rectum presents a much more challenging surgical problem, as the mesentery is tightly compacted in space that is not easily accessible and radial margins are confined by the bony pelvis. Therefore, the recurrence pattern after curative surgery for rectal carcinoma has been both systemic as well as local. Furthermore, re-establishment of intestinal continuity and bowel function are similarly more challenging after surgery for rectal carcinoma as compared to colon carcinoma because safe anastomosis is not readily accomplished in the deep pelvis. The loss of a significant portion or the entire rectum causes bowel function alterations that require separate consideration. This portion of the newsletter will focus on examining the impact of several surgical procedures on local control of tumor and the functional consequences of such surgery.

The consequences of LR are profound disability, pain and suffering as a result of tumor-causing obstruction, fistula and direct invasion of pelvic structures, most notably the sacral nerves. While functional considerations considerations are no doubt very important, and will be discussed, we emphasize that the primary endpoint of any surgical approach for the treatment of rectal carcinoma is local control of the tumor.

Surgical Anatomy
The anatomy of the rectum can be confusing as surgeons and anatomists do not necessarily use the same terms to describe the same structures. The anatomist would state that the anus extends from the anal verge to the dentate line, while the surgeon refers to the anal canal, which includes the anatomic anus as well as the full length of the sphincter complex and includes the pelvic floor musculature. This would include mucosa between the dentate line and the top of the pelvic floor known as the anal transitional zone and includes elements of both squamous and columnar mucosa. These structures essentially are the organs of anorectal continence and are defined by a tonic state at rest (closed anus). The primary function of the rectum is to serve as a reservoir, and therefore the distance above the anal canal that defines the rectum as a functional unit, not the distance from the dentate line, is of importance. This functional definition of the rectum also defines the anatomic limit of anterior resection. While it is customary to describe the location of rectal carcinoma as distance from the anal verge, the tumor’s relationship to the top of the anal canal is of greater use when making decisions regarding tumor resectability and preservation of the anal canal. Typically, the anal canal is about one centimeter longer in men compared to women (3.5 versus 2.5 cm) and shortens with age. The rectum is about 10-12 cm in length, with the proximal third located within the peritoneal cavity. The lymphvascular pedicle is tightly compacted posterior to the rectum and together with the rectum is surrounded by thickened visceral peritoneum called the fascia propia.