Fungal Infections and Anal Fissures
Fungal infections in the anus do not cause anal fissures. Anal fissures arise from mechanical trauma and internal anal sphincter hypertonia with resultant ischemia, not from infectious etiologies including fungal infections 1.
Primary Etiology of Anal Fissures
The exact etiology of anal fissures remains incompletely understood, but the dominant mechanism involves:
- Ischemic ulcer theory: Manometric studies demonstrate a strong correlation between internal anal sphincter hypertonia and decreased anodermal vascular blood flow 1
- Mechanical trauma: While passage of hard stools is implicated, less than 25% of patients with anal fissures actually complain of constipation, indicating this is not the sole or primary mechanism 1
- Location pattern: Approximately 90% of anal fissures are located posteriorly in the midline, with anterior fissures occurring in 10% of women versus 1% of men 1
When to Suspect Atypical Causes
Fungal infections, along with other infectious etiologies, should only be considered when fissures are atypical in presentation 1. Atypical features that warrant investigation for alternative causes include:
- Lateral location of the fissure in the anal canal 1
- Multiple fissures 1
- Associated diseases such as inflammatory bowel disease, sexually transmitted diseases (HIV, syphilis, herpes), anorectal cancer, or tuberculosis 1
In HIV-seropositive patients specifically, while fungal infections can occur in the anorectum, the predominant infectious causes of anorectal disease are herpes (50%), cytomegalovirus (25%), Neisseria gonorrhoeae (16%), and chlamydia (16%), not fungal pathogens 2.
Clinical Approach to Suspected Atypical Fissures
For patients with atypical anal fissures (lateral location, multiple fissures, or in immunocompromised/diabetic patients):
- Collect focused medical history assessing for inflammatory bowel disease symptoms (diarrhea, weight loss, abdominal pain), immunocompromised status, diabetes, and sexually transmitted disease risk factors 1
- Perform complete physical examination including careful inspection of the perineum for surgical scars, anorectal deformities, signs of perianal Crohn's disease, and digital rectal examination 1
- Laboratory testing should be guided by suspected associated illness to rule out other causes 1
- Advanced investigations (endoscopy, CT scan, MRI, or endoanal ultrasound) are suggested only when there is suspected concomitant inflammatory bowel disease, anal or colorectal cancer, or occult perianal sepsis 1
Common Pitfalls
Do not attribute typical midline anal fissures to fungal or other infectious causes without evidence of atypical features 1. The overwhelming majority of anal fissures are cryptoglandular in origin, related to sphincter dysfunction and ischemia, not infection 1, 3.
In immunocompromised patients or those with diabetes, while the threshold for investigating infectious causes should be lower, the fundamental pathophysiology of typical anal fissures remains unchanged 1.