An Overview of Rectal Surgery

By Jacob A. Greenberg, M.D., Ed.M., and Ronald Bleday, M.D.

I. Introduction

When a person hears about rectal surgery, they often react with fear. Since the rectum is often a source of both benign and malignant disease, it is frequently treated with medications or surgery. But when hearing of the need for surgery, patients often worry about the need for an ostomy or “bag.” The goal of this Knol is to give you a brief overview of the types of surgery performed on the rectum. While it may be somewhat technical, our goal is to be comprehensive and accurate so that you can discuss with your surgeon the major issues involved with any rectal operation. We will start with a discussion of surgery for rectal cancer and then discuss surgery for benign (non-cancer) conditions.

II. Surgery for Rectal Cancer

Each year in the United States, approximately 42,000 patients are diagnosed with rectal cancer¹, and 8,500 patients will die of this disease. While the treatment of rectal cancer frequently involves chemotherapy and radiation, surgical resection (removal by surgery) is essential for cure. The five-year survival rates following potentially curative surgical resections vary based on the stage of the disease, and generally range from 80-90% for patients with stage I disease down to 30-40% for patients with stage III disease.
The surgical management of rectal cancers depends on a number of factors, including stage, tumor size, location within the rectum, depth of invasion into the wall of the rectum, and involvement of the sphincter complex (the muscles responsible for the voluntary control of defecation). Select patients with small, superficial tumors with no evidence of spread to the lymph nodes may be candidates for limited surgery via a local excision. However, the majority of patients will require more extensive procedures such as low anterior resection (LAR) or abdominoperineal resection (APR) for management of their rectal cancer. This last operation is the procedure that leads a patient to having a permanent ostomy or “bag.” It is only recommended as a last resort, however, many patients live productive and active lives with the ostomy.

a. Anatomy of the Rectum

            The rectum comprises roughly the last 20 centimeters of the large bowel. While it is similar to the rest of the colon in that it contains the same layers of tissue, there are some distinct anatomic considerations that make rectal surgery different from colon surgery. The upper rectum begins within the abdominal cavity and can be identified at the point where three longitudinal strips of muscle (the tenia coli) converge. From there, the middle rectum descends within the bony pelvis and runs between the sacrum and the bladder/prostate in males and the sacrum and uterus/vagina in females before terminating at the anus. Several nerves, including those responsible for proper sexual function in both sexes, run in close proximity to the rectum, and care must be taken to preserve the nerves during any operation.
            The blood supply to the rectum comes from several different sources. The superior rectal artery arises as the end branch of the inferior mesenteric artery. The middle rectal arteries are branches off of the internal iliac arteries, and the inferior rectal arteries come from the pudendal arteries. The venous drainage follows these three different arteries and therefore can either go to the liver, or bypass the liver through the internal iliac veins into the inferior vena cava. This is important, as it can allow metastases (cancer growth away from primary tumor) to travel not only to the liver, but also to other distant sites like the lungs and brain without traveling to the liver first.
            In the lower rectum, there are a number of muscles referred to as the sphincter complex that are responsible for the voluntary control of bowel movements. These muscles are left intact whenever possible in order to prevent incontinence postoperatively. However, in certain situations, it becomes necessary to sacrifice the sphincter complex and leave patients with a permanent ostomy. This will be discussed in greater detail below.

b. Resection Margins

            The term margin refers to the distance between the edge of the surgically resected specimen and the edge of the tumor. Gross margins are calculated based on the edge of the tumor as it can be seen with the naked eye, while pathologic margins are determined using the microscopic edge of the tumor. In surgery for rectal cancer, there are three margins of interest: the proximal margin, the distal margin, and the radial margin.
            The proximal margin refers to the distance between the proximal cut edge (the edge of the specimen that is closer to the mouth) and the beginning of the tumor. It is currently recommended that this margin be at least 5 centimeters in length². While the proximal margin is certainly important, the distal margin and radial margin are more critical for preventing local recurrence of rectal cancer.
            The distal margin, which refers to the distance between the end of the tumor and the cut end of the specimen that is closer to the anus, has been a subject of great debate. The traditional belief was that a 5-centimeter margin was necessary for an adequate surgical resection. However, more recent studies have shown that there were no statistically significant differences in rates of local recurrence or survival between patients with <2cm, 2 to 2.9cm, and >3cm margins³. Therefore, the current recommendations are for a distal margin of at least 2cm whenever possible², however, a shorter margin is sometimes accepted if this means that the patient will be spared a permanent colostomy. Radial margins refer to the circumferential amount of normal tissue between the edge of the tumor and the edge of the resected tissue. The importance of adequate radial margins in the prevention of local recurrence has only recently been appreciated, but appears to be beneficial both in terms of decreased local recurrence as well as improved overall survival. The importance of negative radial margins has led to the acceptance of the Total Mesorectal Excision (TME), which will be discussed in further detail later in this chapter.

c. Bowel Preparations

             The goal of mechanical bowel preparation (cleansing of the bowel) is to reduce the amount of feces in the colon. This in turn makes the bowel easier to handle during the operation and reduces the chance of fecal spillage, which can lead to contamination of both the abdominal cavity and the wound. Most surgeons prefer preparation of the bowel prior to surgery with a mechanical bowel preparation, as well as a combination of oral and intravenous antibiotics. The addition of oral and intravenous antibiotics reduces the bacterial count of the colon and helps prevent infection should fecal contamination occur.
            Most bowel preparations will require that you eat no solid foods the day before surgery. Instead, you will likely be instructed to have only clear liquids on the day prior to surgery and then nothing from midnight on.  A number of products are currently used for mechanical bowel preparation, and the choice of bowel prep depends on your other medical illnesses as well as surgeon preference.
            Polyethylene Glycol (PEG), which is used in products like GoLYTELY and NuLYTELY (http://www.nulytely.com/), is administered as a 4-liter solution that is drank the day prior to surgery. Patients are instructed to drink roughly 8 ounces every 15 minutes over 4 to 6 hours or until their bowel movements are clear of particulate matter. This regimen is not associated with severe electrolyte imbalances and therefore is ideal for patients with kidney disease. However, the large volume of salty-tasting liquid that must be drank can lead to nausea, bloating, and vomiting and should not be used in patients with disorders of gastric motility such as diabetes.
            Sodium phosphate solutions, such as Fleets Phospho-soda(http://www.phosphosoda.com/), are an alternative to PEG preparations. It is usually given as two separate doses of 45mL of medication, each diluted in a glass of water. It does not require the ingestion of large volumes of fluid used for the PEG preps, but has been associated with some severe electrolyte disorders and should be avoided in patients with renal failure, cirrhosis, ascites (a collection of fluid in the abdomen), and a number of other medical conditions. Enemas can also be given on the morning of surgery to further wash out any particulate matter that may remain following either of these preparations.
            The oral antibiotics administered as part of some bowel preparations are either minimally absorbed or not absorbed at all, and therefore help decrease bacterial counts in the colon. Most surgeons use a combination of neomycin and erythromycin, but some have started using a combination of ciprofloxacin and metronidazole to avoid the cramping associated with erythromycin. Intravenous antibiotics are given before incision, so that they reach maximal tissue levels at the time of operation. The use of intravenous antibiotics decreases a variety of postoperative infectious complications and is well supported in the literature.

d. Standard Resections

            Two different standard resections are employed in the treatment of rectal cancer: the low anterior resection and the abdominoperineal resection. Both of these operations involve the removal of portions of the rectum through similar operative techniques. However, there are some important differences, which will be discussed in the following sections.

Low Anterior Resection

            Low Anterior Resection (LAR) involves the removal of a portion of the rectum including the tumor, while maintaining continence by preserving the sphincter complex. LAR is the treatment of choice for upper and middle rectal lesions as well as some lower rectal lesions where there is enough distance between the end of the tumor and sphincter complex to ensure a 2cm distal margin. Therefore, during an LAR, the sphincter complex is preserved and the patient should have normal or near-normal bowel control as long as they do not require a temporary diverting ileostomy, which will be discussed later.
            The LAR begins with an incision in the middle of the abdomen that usually starts beneath the belly button and extends downwards towards the pubic bones. The fatty and muscular tissue beneath the skin is also divided in the midline until the abdominal cavity is entered. After placing a variety of retractors (surgical instruments used to hold tissue or organs out the way) that help to obtain an isolated view of the colon and rectum, the rectum is dissected (separated) free of its surrounding attachments and care is made to divide large blood vessels with minimal blood loss. The rectum is divided proximally and the dissection is carried down in the pelvis making sure to excise the rectum as well as its surrounding fatty tissue, referred to as the mesorectum. Care is also taken to identify and preserve the ureters, which are the tubes that drain urine from the kidneys into the bladder, and the nerves, which are responsible for sexual function. The dissection is carried down below the level of the tumor and the rectum is stapled off distally. At this point the surgeon can choose a variety of techniques to reconstruct the bowel. Frequently, a stapling device is used to reconnect the two ends (see Figure 1), and other times the surgeons will sew the two ends together by hand. In the majority of cases, the operation ends at this point and the abdomen is closed. In certain situations, such as a very low anastomosis, previous radiation to the pelvis, or any concern about the anastomosis (reconnection of the two ends of the bowel), the surgeon may choose to create a temporary ileostomy (an ostomy created out of the small intestine) to divert the stream of feces and provide the anastomosis with the adequate environment for healing.

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