The effects of topical application of metronidazole for treatment of chronic anal fissure: A randomized, controlled pilot study.

BACKGROUND

Chronic anal fissures (CAFs) rarely heal with conservative management. Because they are associated with strong anal sphincter tone, most treatment aim to reduce anal pressure. Although infections can cause fissures, as can traumatic injury to the anal canal, antimicrobial treatment is not recommended. In a previous study, we reported identifying a wide spectrum of pathogenic microorganisms in the bases of CAFs, anaerobic bacteria being present in half the cases. We postulated that microbial colonization delays healing of CAF and aimed to determine whether decreasing the bacterial load with topical antibacterial treatment accelerates fissure healing.

METHODS

We cultured fecal samples and swabs from the bases of CAFs in 103 patients. Patients in whose samples anaerobic bacteria were identified (47 patients) were then invited to participate in a prospective randomized clinical trial comparing topical metronidazole with conventional treatment. The primary endpoint was fissure healing confirmed on anoscopy. Secondary endpoints of maximum pain on defecation assessed by visual analog scale, maximum anal resting pressure, and rectal pH were recorded on entry and at 10, 21, and 28 days.

RESULTS

The CAFs were colonized by mixtures of gram-positive/gram-negative anaerobic bacteria or gram-negative aerobic monocultures. Patients with anaerobic bacteria in their swabs who received topical metronidazole treatment experienced rapid relief of pain and anal sphincter spasm along with enhanced fissure healing (95.6 % healing rate compared with 70.8 % in the control group, p = 0.048).

CONCLUSION

Topical antimicrobial treatment can be effective in patients with CAF provided the relevant microorganisms are correctly identified.