Effect of topical glyceryl trinitrate on anodermal blood flow in patients with chronic anal fissures

Introduction: Recent studies have highlighted the role of increased internal anal sphincter pressure and decreased anodermal blood flow in the pathogenesis of chronic anal fissures. The duration of the effect of topical 0.2% glyceryl trinitrate (GTN) ointment on anodermal blood flow in fissure and normal areas was investigated in patients with chronic anal fissures. Methods: Six patients with chronic anal fissures in the posterior midline participated in the study. Blood flow measurements were performed on the anoderm using laser Doppler flowmetry before and immediately after the topical application of 0.2% GTN ointment and subsequent readings were taken at 5, 15, 30, 45 and 60 min in all four quadrants. Results: The mean anodermal blood flow in the fissure region is significantly lower than the mean blood flow of the rest of the anoderm before 0.2% GTN ointment is applied (228.7 +/- 61.8 flux units vs 439.3 +/- 25.5 flux units, respectively; P < 0.05). Immediately after the application of local 0.2% GTN ointment there is a significant increase in anodermal blood flow over the anal fissure region (457.8 +/- 56.5 flux units; P < 0.05) compared to the rest of the anoderm (457.4 +/- 30.8 flux units). This increase is most marked at 5 min post-GTN ointment application in the fissure area (474.6 +/- 41.1 flux units) and the blood flow in the fissure region is consistently above the rest of the anoderm for most of the 60 min. Conclusion: There is clearly reduced blood flow to the chronic anal fissure region compared to the rest of the anoderm. Topical application of glyceryl trinitrate ointment seems to significantly improve the blood flow to the fissured area in the first hour. This may therefore help in the healing of chronic anal fissures.