Rectal Surgery for Rectal Cancer
What is Rectal Cancer?
The rectum is defined as the last 8-9 inches of the colon ending at the anus. It is responsible for storing and evacuating stool. The lining of the rectum is identical to that of the colon and thus the most common rectal cancer is an adenocarcinoma or a cancer which arises in the glands which line the rectum and make mucus. Rectal cancers may be detected by the examining finger, rigid proctoscopy, flexible sigmoidoscopy or a colonoscopy. As with any other cancer a biopsy with examination under a microscope is required to confirm the diagnosis.
How is Rectal Cancer Evaluated?
Additional work-up is similar to that of colon cancer (CT scan of the abdomen and pelvis, chest x-ray, CEA blood test, and chest x-ray with or without a PET scan). Rectal cancers are also often evaluated by a technique called endorectal ultrasound. This typically involves the use of a colonscope with an ultrasound probe on the end which is placed in the rectum and allows the examiner to determine with 70% accuracy the depth of invasion of the tumor and with 50-60% accuracy whether or not it has spread to surrounding lymph nodes.
With the ultrasound result the depth of tumor penetration can be gauged. “T1” means a tumor is only in the lining of the rectum. “T2” means the tumor is into, but not through the muscular wall of the rectum and thus would have an approximately a 22% chance of spreading to lymph nodes based purely on the depth of penetration. “T3” means the tumor has grown all the way through the rectal wall and into the perirectal fat and would have a greater than 50% likelihood of at least microscopic spread to local lymph nodes. “T3” tumors that are in the lower two-thirds of the rectum should receive radiation treatment to minimize the risk of cancer recurring in the pelvis by 50%. If this radiation is given preoperatively, approximately 15-20% less radiation is required to achieve the same therapeutic effect than if it is given after surgery. Thus, a surgeon will likely recommend preoperative radiation therapy for ultrasound stage T3 tumors in the lower two-thirds of the rectum.
Since tumors in the upper reaches of the rectum behave very much like colon cancer, radiation is rarely required either before or after surgery. In addition, most “T1” tumors and some “T2” tumors may be amenable for a technique known as transanal excision where using very specialized equipment under general anesthesia, a special retractor is placed in the anus and instruments are used to reach through the anal opening into the rectum and remove the tumor with a margin of normal tissue and then close the incision internally with dissolvable sutures. Patients amenable to transanal excision normally require only an overnight stay in the hospital.
Preparing for Rectal Cancer Surgery
Rectal cancer surgery preparation is usually identical to that for colon surgery. Postoperative care instructions are similar to those following colon cancer surgeries with the exception of patients undergoing transanal endoscopic microsurgery(TEM). TEM was pioneered in Germany approximately 25 years ago. Less than 130 centers in the United States practice this technique.
Doctor Bishop trained in Germany in 2006 under Dr. Gerhardt Buess, the originator of the technique. He has by far the most experience in the state of Alabama with this technique and has performed approximately 100 rectal lesion resections using the transanal endoscopic microsurgery equipment at Trinity Medical Center.
Rectal surgery not amenable to transanal excision can many times be resected laparoscopically. For rectal cancers very close to the anus sometimes open surgery with removal of most of the rectum, but sparing the sphincters, can be done resulting in what is known as a coloanal anastomosis. Rarely the cancer is large enough and low enough that the entire rectum and anus must be removed (abdominoperincal resection) necessitating a permanent end sigmoid colostomy.