Anoscopy: Purpose and Procedure
Anoscopy should be performed as part of the physical examination in all patients with suspected anorectal conditions whenever feasible and well tolerated, as it demonstrates superior accuracy (99% detection rate) compared to flexible endoscopy in identifying hemorrhoids, anal fissures, polyps, and other anorectal lesions. 1, 2
Primary Purpose
Anoscopy serves as the essential diagnostic tool for direct visualization of the anal canal and distal rectum, enabling detection of:
- Hemorrhoids (both internal and external) with 99% accuracy compared to 78% with fiberoptic instruments 2
- Anal fissures - visible tears in the anal mucosa 3, 4
- Anal polyps - benign tissue growths projecting from the anal canal mucosa 5
- Other anorectal masses including condylomas, abscesses, anorectal prolapse, or cancer 1
The Procedure
Equipment and Technique
- Uses an Ive's slotted anoscope with adequate light source for optimal visualization 3
- Takes less than one minute to perform and is easily learned 2
- Provides superior detection compared to straight withdrawal (78%) or retroflexion (54%) with flexible endoscopy 2
Clinical Context and Limitations
Critical caveat: Anoscopy cannot be performed adequately in patients with thrombosed or strangulated hemorrhoids due to excruciating anal pain in awake patients. 1
- Best suited for: Evaluation of painless anorectal bleeding 1
- Requires sedation: Application in hemorrhoidal crisis typically requires proper sedation 1
- Pain indicates: The presence of severe pain strongly suggests external hemorrhoids, fissures, or abscesses rather than polyps 5, 3
When to Proceed Beyond Anoscopy
Do not blindly attribute rectal bleeding to hemorrhoids - this is a critical pitfall that can delay diagnosis of serious conditions. 1, 6
Colonoscopy is indicated when:
- Concern for inflammatory bowel disease or cancer based on personal/family history 1
- Painless rectal bleeding with atypical features 6, 7
- Positive fecal occult blood test (never attribute to hemorrhoids without investigation) 6
- No source evident on anorectal examination despite symptoms 6
- Significant risk factors for colonic neoplasia present 6
Imaging (CT, MRI, endoanal ultrasound) only if:
- Suspicion of concomitant anorectal diseases including sepsis/abscess, inflammatory bowel disease, or neoplasm 1, 7
- Hemodynamic instability or severe bleeding requiring urgent intervention 7
Common Diagnostic Pitfalls
- Mistaking conditions: Multiple anorectal conditions present similarly - up to 20% of hemorrhoid patients have concomitant anal fissures 5, 6
- Inadequate examination: Attributing symptoms to hemorrhoids without proper anoscopic visualization 5
- Missing occult pathology: New-onset anal pain without visible source may indicate small intersphincteric abscess 5
- Assuming benign cause: 10-15% of patients with severe hematochezia actually have an upper GI source 7