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Center for Colon and Rectal Surgery
SIGMOIDOSCOPY AND THE OFFICE DIAGNOSIS OF COLORECTAL TUMORS (POLYPS AND CANCER)

Colorectal cancer can be diagnosed in the office if the lesion is within reach of a lower GI endoscope, usually a sigmoidoscope (rigid or flexible) or anoscope. The diagnosis of cancer is suspected on the basis of characteristic visual findings and is confirmed with a biopsy.

Many practitioners are familiar with using the flexible sigmoidoscope which will reach and diagnose about 60% of all colon and rectal cancers. Physicians should also learn to use the rigid sigmoidoscope and the anoscope which help in the diagnosis of low lying rectal and anal canal tumors.

SYMPTOMS
Patients with colorectal tumors may be asymptomatic or may present with complaints of rectal bleeding, mucous discharge, change in stool caliber or tenesmus. Bloating or abdominal cramps may also be noted. All too often, bleeding from a tumor is incorrectly attributed to hemorrhoids by the patient or even by the doctor. To avoid this problem, all patients presenting with rectal bleeding should have a sigmoidoscopy as part of their examination and workup.

PREPARATION
Dietary restriction prior to sigmoidoscopy or anoscopy is unnecessary. The patient should take one Fleet enema one to two hours before coming to the office. Antibiotics are not routinely given unless the patient is immunosuppressed, has a prosthesis (heart valve or artificial joint), or has a cardiac condition that warrants subacute bacterial endocarditis prophylaxis. Even so, antibiotics are not given for diagnostic sigmoidoscopy and are necessary only when a biopsy is performed.

Anticoagulants should be stopped at least 3 days prior to biopsy to normalize the PT and PTT. Aspirin should be stopped at least 1 week prior to biopsy.

TECHNIQUE
Reassurance prior to the examination is paramount. Lower endoscopy has gained an unfair amount of negative publicity. The endoscopic equipment should be discreetly draped over in the exam room rather than be loudly displayed as instruments of anticipated torture.

No sedation is needed if the examination is done gently and skillfully. The patient is placed in the left lateral position, with the hips flexed and legs brought up high to the chest. Any extension at the hips hinders an accurate exam. At first you should look for any anal pathology (masses, fissure, fistula, etc.). The patient should do a valsalva while you look for any prolapsing masses (hemorrhoids, rectal prolapse, or tumor). Then while the patient pushes downward a digital exam is done - the valsalva maneuver relaxes the anal sphincter. The digital exam assesses the sphincter competency and a search for palpable anal canal or lower rectal mass is done. If a mass is found, its exact level from the anal verge should be noted, as well as its size and whether it is fixed to the surrounding tissue (implies local invasion). The digital exam also serves to lubricate the canal for subsequent instrumentation. Anoscopy should be done before sigmoidoscopy or else the air used for insufflation will make anoscopy difficult.

After lubricating the shaft, scope insertion is facilitated if the patient is asked to bear down to relax and open up the anal verge. The scope is inserted pointing toward the patient's umbilicus (the direction of the anal canal). You will feel "give" once the tip is passes the sphincter (about 3 to 4 centimeters).

I prefer the one handed technique keeping my left hand on the control knobs and the right hand on the shaft of the scope to "drive" it upwards. This frees up your assistant to gather biopsies and comfort the patient. Learning to control and drive the scope with your right hand will improve your control of the scope and allow you to negotiate around bends and corners. The goal is to insert the scope as far as comfortably possible using minimal air insufflation. Once you reach the limit of insertion (the patient's limit may be considerably less than that of the 60 cm scope) a careful inspection of the mucosa is done as the scope is slowly withdrawn.

If a tumor (polyp or cancer) is seen, it should be accurately described: location from the anal verge, size, sessile or pedunculated, any white, indurated, ulcerated areas. Biopsy is usually done with an endoscopic cup biopsy forceps placed through one of the scope channels. Pale or white areas or ulcerated areas in a polyp will give the best yield for cancer. If the tumor looks like an obvious cancer, avoid biopsy of the central area of necrosis - the edge of the cancer is the best place to biopsy. At least 3 to 6 biopsies should be done. I do not recommend using electrocautery snare or hot biopsy through the sigmoidoscope as the patient has not had a complete bowel prep. In such a case gas explosion can occur and if unprepped bowel is perforated, the results are disastrous.

HANDLING THE SPECIMEN
The specimen should be placed immediately into a fixative solution (usually formalin) and should not be allowed to dry out. Communication with the pathologist is critical. The specimens should be labelled and may need orientation. Along with the biopsy should be a short history and a description of the lesion biopsied: was the lesion sessile or peduculated?, what was the location - anal canal, rectum?

PROBLEM AREAS
1. Should any biopsy be performed at all?
If the polyp is over 5mm, it is likely an adenoma and one can make the argument of forgoing a biopsy and go directly to colonoscopy after a formal complete bowel prep. Polyps under 5mm are likely hyperplastic and have no malignant potential. At the time of colonoscopy the entire polyp can be removed and a search for synchronous polyps (30%) in the rest of the colon can be done. If the lesion is in the high rectum (over 10 cm from the anal verge) or in the sigmoid colon and has the appearance of cancer, biopsy will not add to the management as formal resection is indicated. However, in such a case the remainder of the colon must still be examined with colonoscopy or barium enema X-ray because of the high incidence of synchronous lesions (30% polyps, 5% cancers). If a mass is suspicious for cancer in the low to mid rectum (4 to 10 cm) a biopsy is mandatory before embarking on surgery, as excision of lesions at this level may require an abdominoperineal resection. This radical surgery should rarely be done for benign lesions therefore the lesion must first be proven as malignant. Occasionally I have had to take such a patient to the operating room for a biopsy under anesthesia. Another reason to obtain a biopsy for low rectal lesions is that in rare cases what appears to be an adenocarcinoma may in fact be squamous cell carcinoma or lymphoma. The treatment for the latter two cancers is not primarily surgical and may require chemotherapy of radiation.

2. Large sessile polyp - where do you biopsy?
The goal of the biopsy is to obtain a representative sample. This may not be possible for large polyps and a small focus of cancer may be missed. Any lesion over 2 cm has a 50% chance of harboring a cancer. Again, the best approach is to biopsy any suspicious areas of the polyp (white, pale or ulcerated areas). If all the biopsies are benign and if the lesion is low, a transanal excision of the entire polyp is indicated. If the lesion is high, a bowel resection is indicated if the polyp can not be removed endoscopically.

If malignancy is noted on biopsy of a low rectal lesion, subsequent treatment depends on the level of invasion. Clinically, if the cancer is tethered to the muscle or there are palpable perirectal lymph nodes, this implies an advanced stage. Rectal ultrasound can also tell the level of invasion. If the invasion is only to the submucosa then local excision for cure is possible. If the underlying muscle is deeply invaded a radical excision is called for as incidence of lymph node metastases increases. If only superficial muscular invasion is demonstrated on rectal ultrasound and clinical examination, treatment options will have to be discussed with the patient.

3. Lesion looks like obvious cancer but repeated biopsies are negative.
The management of such a case depends on the level of the lesion. If the lesion is in the high rectum or sigmoid colon, more biopsies are not indicated and the patient should be prepared for radical surgery. Lesions in the low to mid rectum should have repeat biopsies done to look for cancer even if done under anesthesia before radical surgery.

4. How accurate are measurements done with the flexible sigmoidoscope?
Because the instrument is flexible, the measure of the level of the lesion is often inaccurate. For lesions in the rectum where there exists a possibility of an abdominoperineal resection and colostomy, rigid sigmoidoscopy should be done. This will give an accurate measure of the level of the lesion before surgery. Rigid sigmoidoscopy also permits the operator to use larger biopsy forceps to obtain larger tissue samples but this will also increase the risk of complications such as bleeding and perforation.

5. Role of anoscopy?
The anoscope allows the anal canal and low rectal mucosa to be seen. Lesions in these areas may be missed with the flexible sigmoidoscope. Fortunately these lesions should not escape detection by the examining finger but this does occur rarely. Because the area visualized by the anoscope may have some somatic innervation, biopsy without some sort of anesthetic may be impossible.

6. How do you manage a rectal submucosal mass?
On occasion a palpable or visible rectal mass is found covered by normal mucosa. A cup biopsy through the flexible sigmoidoscope may only yield mucosa and may not be diagnostic. A fine needle aspiration through the scope may yield enough cells to make a diagnosis. If more tissue is needed, a biopsy with an alligator forceps through the rigid sigmoidoscope or a transanal biopsy under anesthesia is indicated. Soft tissue tumors, lymphoma, and carcinoids can present as a rectal submucosal mass.

COMPLICATIONS OF BIOPSY
Bleeding is the most common complication and occurs in 1 to 2 % of the time. The bleeding can be obvious immediately or delayed for up to 2 weeks later. Bleeding almost always stops spontaneously. Immediate bleeding can be managed by pressing a long Q-tip soaked in epinephrine solution against the bleeding area through the rigid scope or injecting the area submucosally with epinephrine solution.

Perforation can occur due direct trauma by the sigmoidoscope or due to biopsy. It can be intraperitoneal (free air and peritonitis) or it can be extraperitoneal. The management depends on the patient's clinical presentation. Evidence of peritonitis and sepsis demands immediate surgery, while a stable patient may be treated with close observation and antibiotics.

Gas explosions can occur if electrocautery is used to biopsy or remove polyps in patients with unprepared bowel. Since most patients coming for sigmoidoscopy have not had a full bowel prep, electrocautery should never be used.

Barium enema perforation is prevented by avoiding this study immediately after a sigmoidoscopic biopsy.

Many of the problems associated with sigmoidoscopy can be avoided by using common sense and acquiring skills that come only with experience.

Copyright 2007 Center for Colon and Rectal Surgery, 864 Second Street, Santa Rosa, California 95404 U.S.A. All rights reserved.