An anoscopy is a quick, in-office exam that lets a doctor look inside the anal canal and the lowest part of the rectum. It uses a small, rigid tube called an anoscope, typically about 9 centimeters (roughly 3.5 inches) long and less than an inch in diameter, with a built-in light. The whole thing takes just a few minutes, requires no sedation, and in most cases needs no special preparation beforehand.
Why Doctors Order an Anoscopy
The most common reason is rectal bleeding. An anoscopy is better at detecting problems like internal hemorrhoids, inflammation, tears, ulcers, and small masses than even a flexible sigmoidoscopy, which examines a larger stretch of the bowel but can miss issues right at the anal opening. Because the anoscope holds the anal canal open and illuminates it directly, the doctor gets a clear, close-up view of tissue that’s otherwise difficult to examine.
Beyond bleeding, an anoscopy may be recommended for:
- Anal or rectal pain, such as from fissures or thrombosed hemorrhoids
- Perianal itching or discharge
- Warts (condylomata) inside the anal canal
- Screening for anal cancer or precancerous changes, especially in high-risk groups
- Evaluating trauma or a mass felt during a digital rectal exam
- Fecal impaction or foreign body retrieval
- Changes in bowel habits that suggest a problem near the rectum
How It Compares to Other Exams
An anoscopy examines only the anal canal and the very end of the rectum. A proctoscopy goes further, reaching into the rectum and sometimes part of the sigmoid colon. A colonoscopy covers the entire colon, from the rectum all the way to where the small intestine connects. These procedures serve different purposes. If the suspected problem is localized to the anus, an anoscopy is the most direct and sensitive tool. If the concern involves the broader colon, a colonoscopy is the appropriate choice.
What Happens During the Procedure
You’ll typically lie on your side with your knees drawn toward your chest. The doctor lubricates the anoscope and gently inserts it into the anal canal. You’ll feel pressure, similar to the sensation of a bowel movement, but the procedure is not typically painful. Because the anoscope is short and slim (about 18 to 23 millimeters in diameter), it doesn’t stretch the area significantly.
Once the anoscope is in place, the doctor slowly withdraws it while examining the lining of the canal under the light. If something looks abnormal, they can take a small tissue sample (biopsy) or a swab right then. The entire exam usually lasts only a few minutes.
Preparation and Risks
A standard anoscopy generally requires no bowel prep, no fasting, and no enema. This is one of its advantages over more involved procedures like colonoscopy. Some doctors may recommend a small enema beforehand if the exam is combined with a more extensive rectal procedure, but for a routine anoscopy this is uncommon.
Risks are minimal. The procedure is considered very safe. If a biopsy is taken, there’s a slight chance of minor bleeding and mild discomfort at the biopsy site, but serious complications are rare.
High-Resolution Anoscopy
High-resolution anoscopy, or HRA, is a specialized version of the standard exam. It pairs the anoscope with a magnifying device called a colposcope, which allows the doctor to spot tiny tissue changes invisible to the naked eye. During HRA, a dilute vinegar solution (acetic acid) is often applied to the anal lining. Abnormal cells absorb the solution differently, making precancerous patches easier to identify.
HRA is primarily used to screen for anal dysplasia, which are cellular changes that can eventually develop into anal cancer. It’s recommended as a follow-up when initial screening tests, like an anal Pap smear, come back abnormal. People at higher risk for anal cancer, particularly those living with HIV, benefit most from this type of targeted screening. Current guidelines recommend HRA during follow-up for anyone whose initial screening results are abnormal, though the exact threshold for referral varies between medical organizations.
What Results Can Show
If the anoscopy looks normal, you’ll typically hear that right away. If the doctor finds hemorrhoids, fissures, or inflammation, they can often discuss a treatment plan in the same visit. Some hemorrhoid treatments, like rubber band ligation, can even be performed through the anoscope during the same appointment.
If a biopsy was taken, results usually come back within a week or two. Biopsy findings might show benign inflammation, wart tissue, precancerous cells (dysplasia), or, less commonly, cancer. Your next steps depend entirely on what the tissue shows, and your doctor will walk you through options once the results are in.