screening of healthy, asymptomatic adults for colorectal cancer1

evaluation of the patient with suspected lower gastrointestinal pathology in combination with a barium enema study (by itself, the barium radiographs may be insensitive in the distal colon)

management of lower gastrointestinal bleeding; in selected patients this procedure can detect bleeding polyps, fissures, etc

evaluation of the patient with suspected inflammatory disease of the colon, such as inflammatory bowel disease, infectious colitis, sigmoid diverticulitis, and others

More controversial indications include:

temporary decompression of sigmoid volvulus (recurrence of the volvulus is common without prompt surgery)

cancer surveillance in patients who have undergone surgical resection of a sigmoid colon neoplasia (to rule out recurrence at the anastomosis)

Contraindications Few absolute contraindications exist for this procedure. However, the procedure should best be avoided in the following high-risk situations:

severe diverticulitis

acute peritonitis

toxic megacolon

severe underlying cardiac or pulmonary disease

uncorrectable coagulopathy

acute intestinal perforation

massive GI bleeding

In addition, flexible sigmoidoscopy should not be performed in situations where colonoscopy is indicated (see Colonoscopy). This includes polypectomy which should be performed by colonoscopy.

Patient Preparation Details of the procedure are discussed with the patient, including goals, technique, and risks. Informed consent is obtained. A number of preparative bowel regimens have been proposed. One popular and effective regimen is administration of a single phosphosoda (FleetŪ) enema several minutes before sigmoidoscopy. This results in an adequate bowel prep in nearly 90% of patients. Other bowel regimens are: two phosphosoda enemas immediately prior to procedure, and oral laxative followed by a single enema. These alternative regimens are also effective. In the majority of cases, premedications such as sedatives, narcotics, or anesthetics are not necessary. (An occasional patient may benefit from a short-acting benzodiazepine.)

Aftercare In general, patients may resume their prior level of activity after sigmoidoscopy. Since sedatives are not administered in most cases, patients may drive home postprocedure.

Special Instructions Due to the risk of bacteremia during sigmoidoscopy, antibiotics may be useful for prevention of bacterial endocarditis in patients with high-risk heart disease. Patients who are at risk for endocarditis include those with prosthetic heart valves, rheumatic valvular disease, previous history of endocarditis, and others. Such patients may benefit from antibiotic prophylaxis, although the risk of endocarditis is low. According to the American Heart Association in 1990,² antibiotic prophylaxis is not recommended on a routine basis for patients without such heart lesions.

Complications Flexible sigmoidoscopy is a safe procedure in skilled hands. Complications that have been reported in the literature include: local pain, bleeding, bacteremia, cardiac arrhythmias, and bowel perforation. The incidence of perforation is quite low, estimated at 0.01% of cases.³

Technique The patient is placed in the left lateral decubitus position on an examination table. Digital rectal examination is performed first. Some physicians routinely perform anoscopy prior to flexible sigmoidoscopy, since the former allows superior visualization of the rectum and anal canal (see Anoscopy). Following this, the sigmoidoscope is lubricated and gently inserted into the rectum. The instrument is then advanced under direct visualization. The physician can direct the tip of the scope using handheld controls and guide the shaft of the instrument with torque. Only a minimal amount of insufflation of the bowel is necessary (unlike colonoscopy). The flexible sigmoidoscope is advanced to its full length, either 35 or 60 cm depending on the model. Areas of pathology are noted. Invasive procedures can be performed as needed, such as biopsy, fulguration, stool sampling, etc. As the instrument is withdrawn, all areas of the intestinal mucosa are inspected again. The rectum is well visualized during withdrawal by retroflexing the sigmoidoscope tip 180° in the final 10 cm.

Specimen All biopsy specimens and cytologic brushings are sent to the Pathology Laboratory promptly. Any tissue or stool samples for microbiological culture should be sent in sterile containers without fixative.

Turnaround Time Final report on biopsy specimens is usually given within 2-3 days. Microbiologic stains, when performed, are often available the same day but bacterial and viral cultures require more time.

Normal Findings Preliminary report on sigmoidoscopic findings is immediately completed by the physician and charted. Final report is given in several days. Important aspects of the examination often commented on include:

indications for procedure

type of instrument used

adequacy of bowel prep

depth of visualization (eg, 35 cm, 60 cm)

appearance of the mucosa

abnormalities such as polyps (size, appearance), pseudopolyps, fissures, neoplasms, ulcers, friable regions, blood, pus, diverticula, and others

therapeutic procedures performed

sites of biopsies

sites of cultures

complications

recommendations

Additional Information The flexible sigmoidoscope is now routinely used in the surveillance of neoplasia-polyps in the asymptomatic patient. The procedure is well-tolerated and safe. It is estimated that about 55% of colon cancers and adenomas are within the theoretic reach of the 60 cm instrument. In reality, most but not all such lesions are detected during sigmoidoscopy. The sensitivity of the 60 cm instrument is about 85% (within its 60 cm range). The 35 cm scope is more comfortable and less expensive than its larger counterpart. Of course, the yield of this instrument is somewhat less, with only 40% of malignant or premalignant colonic lesions within its theoretic range. Again, the sensitivity of this device within its range of 35 cm is about 85%. Recommendations on the use of sigmoidoscopy for cancer surveillance have not been agreed upon.¹ The American College of Physicians recommends screening all adults older than 50 years of age at 3- to 5-year intervals. The following groups also agree with this recommendation: American Cancer Society, National Cancer Institute, and American College of Obstetrics and Gynecology. However, the Canadian Task Force on the Periodic Health Examination refrained from making a specific recommendation on routine screening sigmoidoscopy (although it was considered). The U.S. Preventive Services Task Force also made no specific recommendations for this procedure in adults older than 40 years of age, but felt that sigmoidoscopy should be excluded from routine preventive care in healthy adults from 18-39 years of age. Thus, there is a certain amount of discretion involved on the part of individual physicians regarding the utilization of this procedure.

Footnotes

References