Can you tell me about anoscopy?

Anoscopy: Clinical Overview and Applications

Anoscopy is a fundamental diagnostic procedure that uses a short, rigid tubular instrument to directly visualize the anal canal and distal rectum, and should be performed as part of the physical examination in all patients with anorectal symptoms whenever feasible and well tolerated. 1

What Anoscopy Visualizes and Detects

Anoscopy provides direct visualization of:

• Internal hemorrhoids and their grade/severity 1
• External hemorrhoids and thrombosed hemorrhoids 1, 2
• Anorectal varices (discrete, compressible, serpiginous submucosal veins that cross the dentate line) 1
• Anal fissures, particularly when combined with gentle eversion of the anal canal 1
• Perianal abscesses and fistulas 2
• Rectal mucosal prolapse and skin tags 1, 2
• Suspicious lesions requiring biopsy 3

Anoscopy demonstrates superior diagnostic accuracy compared to flexible endoscopy for anorectal pathology, with a 99% detection rate for anal lesions versus 78% for straight withdrawal flexible sigmoidoscopy and 54% for retroflexion. 4

Clinical Indications for Anoscopy

Primary indications include:

• Bright red rectal bleeding (most common hemorrhoid symptom) 1
• Palpable perianal lump or mass 1, 2
• Anal pain, particularly when associated with defecation 1, 2
• Anal itching or discharge 1, 2
• Suspected hemorrhoidal disease requiring grading 1
• Evaluation of anorectal varices in patients with portal hypertension 1
• Assessment before hemorrhoid banding or other office procedures 3

Technique and Procedural Considerations

The examination requires:

• Adequate lighting (modern disposable anoscopes often include integrated illumination) 3
• Patient positioning in left lateral decubitus or prone jackknife position 2
• Gentle insertion after external inspection and digital rectal examination 1, 2
• Systematic visualization during both insertion and withdrawal 4
• Application of 3% acetic acid for 2 minutes when evaluating for dysplastic lesions (high-resolution anoscopy) 5, 6

The procedure takes less than one minute to perform and is easily learned. 4

Critical Limitations and When Anoscopy Cannot Be Performed

Anoscopy may not be feasible in:

• Patients with thrombosed or strangulated hemorrhoids experiencing excruciating anal pain (requires proper sedation) 1
• Severe anal stenosis (reported in 3 of 14 patients in one study) 7
• Acute perianal abscess with severe tenderness 2

In these cases, examination under anesthesia may be required for adequate assessment. 1, 7

When Additional Evaluation Beyond Anoscopy Is Mandatory

Do not attribute rectal bleeding solely to hemorrhoids without further investigation when:

• Blood is dark red or mixed throughout the stool (suggests proximal source) 1
• Patient has positive fecal occult blood testing 1, 8
• Anemia is present (hemorrhoids alone cause anemia in only 0.5 per 100,000 population) 1, 8
• Patient age >50 years with new-onset bleeding 1
• Personal or family history of colorectal cancer or inflammatory bowel disease 1, 2, 8
• Atypical bleeding patterns (bleeding without defecation, maroon blood) 8

In these scenarios, proceed directly to colonoscopy within 2 weeks for higher-risk cases. 1, 8

Anoscopy vs. Flexible Sigmoidoscopy for Anorectal Pathology

While flexible sigmoidoscopy with retroflexion (J-maneuver) can identify hemorrhoidal disease and low rectal pathology, anoscopy remains superior for:

• Detecting anal canal lesions (99% vs. 54-78% detection rate) 4
• Facilitating therapeutic interventions like band ligation 3
• Providing faster, more cost-effective examination 4
• Enabling precise biopsy of suspicious anal lesions 3, 5

Both the American Society for Gastrointestinal Endoscopy and the Society for Surgery of the Alimentary Tract advocate a minimum of anoscopy and flexible sigmoidoscopy for bright-red rectal bleeding. 1

Therapeutic Applications

Anoscopy enables office-based procedures including:

• Rubber band ligation of internal hemorrhoids (facilitated by fenestrated anoscope designs) 3
• Sclerotherapy injection 1
• Biopsy of suspicious lesions for histopathological diagnosis 3, 5
• Marking of pathology with tattoo injection for surgical planning 1

High-Resolution Anoscopy (HRA) for Dysplasia Screening

HRA uses colposcopic magnification with 3% acetic acid application to detect anal intraepithelial neoplasia in high-risk populations:

• HIV-positive patients (39.1% prevalence of anal squamous intraepithelial lesions) 5
• Men who have sex with men 6
• Patients with history of receptive anal intercourse 5
• Human papillomavirus (HPV) infection (79% prevalence in HIV-positive cohorts) 5

HRA demonstrates 90% sensitivity but only 19% specificity for detecting anal squamous intraepithelial lesions, requiring histopathological confirmation. 5

Common Pitfalls to Avoid

Critical errors include:

• Assuming all anorectal bleeding is from hemorrhoids without performing anoscopy 1
• Failing to perform colonoscopy when red-flag features are present 1, 8
• Overlooking concomitant pathology such as fissures, abscesses, or malignancy 2
• Attempting anoscopy in patients with severe pain without adequate anesthesia 1
• Attributing positive fecal occult blood to hemorrhoids without colonic evaluation 1

Every training program should include instruction in anoscopy technique, as it is essential for complete anorectal evaluation. 4