Anoscopy and Rigid Sigmoidoscopy

Ana DeRoo, MD

John C. Byrn, MD

The routine use of colonoscopy or flexible sigmoidoscopy to examine the rectum and distal colon has not alleviated the need for physicians to become proficient in the use of the anoscope and the rigid sigmoidoscope. The anoscope allows diagnosis and evaluation of conditions such as fistula in ano, perirectal abscess, anal fissure, anal cancer, or perianal Crohn disease and treatment of lesions in the anal canal and distal rectum.¹ Rigid sigmoidoscopy is useful for evaluation of and therapeutic maneuvers in the distal colon and rectum that cannot be performed with the flexible instrument, such as the topical application of formalin in radiation proctopathy and the removal of foreign bodies. In addition, rigid sigmoidoscopy can be performed anywhere there is an electrical outlet, with highly portable equipment that does not require expertise for cleaning or maintenance, as many components are disposable, and without the need for specially trained ancillary personnel. Therefore, rigid sigmoidoscopy is an expedient option in the intensive care unit, emergency department, or other situations requiring rapid use. This section will cover the techniques of anoscopy and rigid sigmoidoscopy.

INDICATIONS

1. Evaluation of symptoms referable to the colon, rectum, or anus: bleeding, discharge, protrusions or swellings, abdominal or anorectal pain, diarrhea, constipation or a change in bowel habits, severe itching
2. Surveillance of colorectal disease including anal and rectal neoplasms
3. Collection of specimen for histologic study (e.g., biopsies for anal intraepithelial neoplasia (AIN)) or stool and/or exudate for bacteriologic or parasitologic study
4. Removal of foreign bodies
5. Application of topical therapy such as formalin in cases of radiation proctopathy or trichloroacetic acid for AIN²,³
6. Injection of medications such as botulinum toxin injection into the anal sphincter for treatment of anal fissures
7. Basic rectal cancer screening examination in areas where flexible sigmoidoscopy or colonoscopy are not available

PREPARATION

1. Obtain informed consent.
2. Have chaperone in room.
3. Antibiotic prophylaxis is no longer recommended for patients undergoing GI endoscopy, unless a high-risk patient (e.g., prosthetic valve, previous infective endocarditis) has an established GI tract infection, at which point prophylactic antibiotics may be considered.⁴
4. Most patients can be examined with no prior bowel preparation.
5. If stool precludes an adequate examination, a bisacodyl suppository, tap water enema, or Fleet (or other proprietary small volume hypertonic phosphate) enema can be given and the examination carried out following evacuation. Outpatients may take the enema at home 1 to 2 hours prior to procedure.
6. Very rarely, an oral preparation with polyethylene glycol electrolyte solution or phospho-soda will be required the day prior to the procedure.
7. Premedication (sedation) is rarely necessary, although intravenous fentanyl and/or midazolam can be useful in unusual circumstances. Institutional sedation guidelines must be followed in such cases. Severely painful conditions may require scheduling examination with sedation or under anesthesia.

EQUIPMENT

Minimal Equipment

1. Anoscope and rigid sigmoidoscope: A variety of sizes are available if the institution uses reusable anoscopes. The disposable plastic anoscope allows for 360° visualization of the anal canal through the transparent plastic. Metal endoscopes frequently have angled tips, providing preferential viewing in one direction as well as end viewing of the anal canal on withdrawal of the instrument.⁵ An adult rigid sigmoidoscope is adequate for all sizes of patient but the infant.
2. Light source: Anoscopes are available with and without an integrated light source.
3. Cotton swab sticks
4. Examination table or bed
5. Sheet to cover the patient
6. Gloves, 4 × 4-in. gauze pads, lubricant (2% topical lidocaine may be useful as a lubricant in painful anorectal disease)