What is an Anal Fissure?
An anal fissure is a longitudinal tear or split in the squamous epithelium of the anal canal, extending from the dentate line to the anal verge, that causes severe pain during and after defecation along with bright red rectal bleeding. 1
Clinical Definition and Anatomy
An anal fissure represents a benign but painful ulceration in the anoderm that creates a visible break in the anal lining. 2 The tear occurs specifically in the squamous epithelium at or just inside the anal verge, making it visible on external examination without requiring instrumentation. 1
Location and Distribution
- Approximately 90% of anal fissures occur in the posterior midline of the anal canal, representing the typical presentation. 3
- Anterior midline fissures account for about 10% in women but only 1% in men. 3
- Any fissure occurring off the midline (lateral or multiple fissures) mandates immediate evaluation for underlying conditions such as Crohn's disease, HIV/AIDS, ulcerative colitis, tuberculosis, syphilis, leukemia, or cancer. 1, 3
Characteristic Symptoms
The hallmark presentation includes two primary symptoms:
- Severe anal pain that typically occurs during and immediately after defecation, with chronic fissure patients experiencing pain lasting many hours after bowel movements. 1
- Bright red, scanty rectal bleeding that patients notice on toilet paper or stool surface. 1
The diagnosis should be suspected based on this characteristic history alone, even before physical examination. 1
Physical Examination Findings
Fissures are best visualized by separating the buttocks with opposing traction to efface the anal canal, allowing direct visualization of the tear without instrumentation. 1, 4
Acute vs. Chronic Features
Acute fissures appear as simple linear tears in the anoderm. 5
Chronic fissures (persisting beyond 8-12 weeks) display specific signs of chronicity: 1, 4, 3
- Sentinel skin tag just distal to the fissure
- Hypertrophied anal papilla at the proximal margin
- Fibrosis at the fissure edges
- Visualization of bare internal sphincter muscle at the fissure base
Underlying Pathophysiology
The condition results from internal anal sphincter hypertonia, which correlates with decreased anodermal vascular blood flow, leading to local ischemia and impaired wound healing. 3, 2 Contrary to common belief, less than 25% of patients with anal fissures actually complain of constipation. 3
Important Clinical Caveat
In the setting of marked pain or tenderness, instrumentation of the anal canal is inappropriate and traumatic to the patient. 1 When significant anal pain cannot be diagnosed comfortably on visual inspection alone, examination under anesthesia is warranted rather than forcing instrumentation. 1