What is the best treatment approach for a patient with low pressure anal fissures and anal atony?

Management of Low Pressure Anal Fissures with Anal Atony

In patients with low pressure anal fissures and anal atony, lateral internal sphincterotomy is absolutely contraindicated, and treatment should focus exclusively on conservative management with fiber supplementation, adequate hydration, warm sitz baths, and topical analgesics—avoiding any sphincter-relaxing pharmacologic agents that would further reduce already-low anal pressures. 1, 2

Critical Pathophysiology Distinction

The standard anal fissure pathophysiology involves internal anal sphincter hypertonia with decreased anodermal blood flow creating an ischemic environment 2. However, your patient presents with the opposite problem—anal atony with already low pressures 3. This fundamentally changes the treatment approach:

• All standard pharmacologic treatments (topical calcium channel blockers, nitroglycerin, botulinum toxin) work by reducing sphincter tone 2, 4, 5
• These agents would be harmful in your patient, as they would further decrease already-low anal pressures 3
• Lateral internal sphincterotomy, which divides the internal sphincter, carries unacceptably high risk of permanent incontinence (10-30%) even in normal-pressure patients and would be catastrophic in anal atony 2, 6

Recommended Treatment Algorithm

First-Line Conservative Management (Indefinite Duration)

• Fiber supplementation of 25-30g daily to soften stools and minimize anal trauma 1, 2, 4
• Adequate fluid intake to prevent constipation 1, 4, 6
• Warm sitz baths to promote local blood flow without affecting sphincter tone 2, 4, 6
• Topical anesthetics (lidocaine 5%) for pain control 2, 6
• Oral analgesics (paracetamol) if topical agents provide inadequate relief 6

What to Absolutely Avoid

• No topical calcium channel blockers (nifedipine, diltiazem)—these reduce sphincter tone 2, 4
• No topical nitroglycerin—this causes sphincter relaxation 2, 5, 7
• No botulinum toxin injections—these paralyze the sphincter 2, 5
• No lateral internal sphincterotomy—this would guarantee incontinence 2, 6, 5
• No manual anal dilatation—this has 10-30% permanent incontinence rates even in normal patients 2, 6

Prognostic Considerations

The presence of anal atony fundamentally worsens the prognosis for fissure healing 3. Research demonstrates that healing probability is associated with a pressure index (PI) ratio between resting and squeeze pressure >150%, similar to healthy controls (200 ± 115%) 3. Your patient with anal atony likely has a PI <150%, predicting failure of even conservative treatment 3.

• Approximately 50% of acute anal fissures heal with conservative care within 10-14 days in normal-pressure patients 2, 8, 9
• This healing rate will be substantially lower in anal atony patients 3
• Healing rates decrease from 100% in symptoms <1 month to 33.3% in symptoms >6 months 7

Evaluation for Underlying Causes

Atypical features mandate investigation for serious underlying pathology 1, 6:

• Anal atony itself is atypical and suggests possible neurologic disease, prior sphincter injury, or inflammatory bowel disease 1
• Consider endoscopy, CT scan, MRI, or endoanal ultrasound to rule out Crohn's disease, anal cancer, or occult perianal sepsis 1, 6
• Fissures off the posterior midline (occurring in only 10% of typical cases) require urgent evaluation 2, 6

Long-Term Management Expectations

There is no definitive cure for fissures in the setting of anal atony 5, 3. The recurrence rate after healing is high even in normal patients (1-3% post-sphincterotomy), and anal fissure may represent a chronic disease that evolves depending on sphincteric features 5. In your patient:

• Continue indefinite conservative management as described above 1, 4
• Pain relief typically occurs within 14 days if treatment is effective 4, 6
• Reassess at 2 weeks for symptom improvement 6
• If no improvement after 8 weeks, the fissure is classified as chronic, but surgical options remain contraindicated 1, 2