Merck Manual

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How To Do Anoscopy


Zubair Malik

, MD, Lewis Katz School of Medicine at Temple University

Reviewed/Revised Feb 2023
Topic Resources

Anoscopy involves insertion of an anoscope into the anus and examination of the anal canal.

Indications for Anoscopy

  • To evaluate anorectal symptoms such as anal pain, discharge, protrusions, or pruritus

  • To evaluate bright red bleeding and provide certain types of hemorrhoid therapy

  • To evaluate any suspected disorder of the anal canal

Contraindications to Anoscopy

Absolute contraindications

  • Shock

  • Acute myocardial infarction

  • Peritonitis

  • Acute bowel perforation

  • Fulminant colitis

  • Absence of an anus due to surgery or a congenital condition

Relative contraindications

  • Cardiac arrhythmias or recent myocardial ischemia (if procedure cannot be postponed, patients will need cardiac monitoring)

  • Recent anal surgery

  • Anal strictures

  • Poor patient cooperation

  • Severe anal pain (procedure would need to be done under anesthesia)

  • Suspected perirectal abscess (based on symptoms)

Complications of Anoscopy

Complications are rare, but the following can occur:

  • Perianal abrasion or mild tear

  • Minor bleeding

Equipment for Anoscopy

  • Gloves

  • 7-cm adult (typically 19-mm diameter) anoscope (slotted or nonslotted); smaller sizes (8- to 14-mm diameter) for children or those with pain or anal stenosis

  • Light source (sometimes built into disposable anoscopes)

  • Lubricating jelly (and topical anesthetic jelly if patient has severe anal pain)

  • Cotton swabs

  • Fecal occult blood test (if needed)

  • Culture tube and swab (if needed)

  • Biopsy forceps (if needed)

The nonslotted anoscope is used for 360° visualization, whereas the slotted anoscope is for visualization of only one portion at a time. The slotted anoscope should not be rotated; it is better for visualization and treatment of hemorrhoids.

Additional Considerations for Anoscopy

  • No bowel prep is needed for anoscopy.

  • The American Heart Association no longer recommends endocarditis prophylaxis for patients having routine gastrointestinal endoscopy.

Positioning for Anoscopy

  • Place the patient in the left lateral decubitus position with knees flexed toward the chest.

  • Other positions, such as lithotomy position, are acceptable if needed.

Relevant Anatomy for Anoscopy

  • The anal canal is about 3 to 5 cm long and connects the distal rectum to the outside.

  • The lower part of the anal canal, below the dentate line, is lined by stratified squamous epithelium. This epithelium has dense innervation by somatic nerve fibers and is quite sensitive.

Step-by-Step Description of Anoscopy

  • Pull the buttocks apart and visually inspect the external area.

  • Insert a lubricated gloved finger to do a routine digital rectal exam (use topical anesthetic jelly if patient has severe anal pain and does not have an allergy).

  • If using a topical anesthetic jelly, wait 1 to 2 minutes to give the anesthetic time to take effect.

  • If there is no gross blood, test any stool obtained for fecal occult blood, if indicated, and change glove on this hand.

  • Lubricate the anoscope and the central guide plug.

  • Slowly insert the anoscope, with the central guide plug in place.

  • After the anoscope is completely inserted, remove the central guide plug (keep the plug available because it may be needed again).

  • If using a nonslotted anoscope, slowly rotate it as you withdraw it and inspect the entire mucosa for masses, lesions, hemorrhoids, or fissures. Any fecal material or blood can be removed with a cotton swab to aid visualization.

  • Culture any abnormal discharge.

  • If indicated, biopsy any suspect mass but only if above the dentate line.

  • If indicated, hemorrhoid therapy can be done in the office.

How to do Anoscopy
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Aftercare for Anoscopy

  • Although no particular aftercare is needed, tell patients to contact their physician immediately if there is significant bleeding or pain after the procedure.

Warnings and Common Errors for Anoscopy

  • Do not biopsy a hemorrhoid or any vascular tissue.

  • Do not rotate a slotted anoscope because doing so can pinch tissue.

  • Do not reinsert the guide plug while the anoscope is inside the patient because doing so can pinch or tear tissue. Remove the anoscope completely, reinsert the guide plug, and then reinsert the anoscope.

Tips and Tricks of Anoscopy

  • Inspection of the external perianal area may be adequate to diagnose causes of severe anal pain such as a fissure, thrombosed external hemorrhoid, or some abscesses; in these cases, digital exam and anoscopy may not be indicated.

  • If prolapse is suspected, a Valsalva maneuver may reveal prolapsing hemorrhoids or mucosa.

  • Asking the patient to bear down while inserting a finger for digital exam or the anoscope may make the insertion easier.

  • Keep one finger pressed on the guide plug (usually your thumb) to prevent it from falling out during insertion until you are ready to remove it.

NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
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