Extent of lateral internal sphincterotomy: up to the dentate line or up to the fissure apex?

The aim of this randomized, prospective study was to compare the results of lateral internal sphincterotomy up to the dentate line or up to the fissure apex in the treatment of chronic anal fissure.

Adult patients with chronic anal fissure were randomly assigned to undergo lateral internal sphincterotomy to the level of the dentate line or to the level of the fissure apex. The patients were reexamined on postoperative Days 1, 7, 14, 28, and then at 2 and 12 months.

The time required for relief of pain postoperatively was 2.08 +/- 1.44 days in the dentate line group, which was significantly shorter than that for the fissure apex group (4.72 +/- 4.86 days; P = 0.002). Objective healing was achieved in 23.7 percent and 17.6 percent at 14 days, 97.4 percent and 88.2 percent at 28 days, and 100 percent and 97.7 percent at 2 months in the dentate line and fissure apex groups, respectively (P > 0.05 for all comparisons). Only sphincterotomy up to the dentate line caused a significant change in anal incontinence (P = 0.016). Both groups had significantly lower anal resting pressures at 4 months postoperatively, compared with their corresponding preoperative levels (P = 0.005 and P = 0.007). The postoperative resting pressures did not differ significantly between the two groups (P = 0.273). By 12 months postoperatively, no treatment failures or recurrences were noted in the dentate line group (100 percent healing rate). In the fissure apex group, there was one nonhealing case and four recurrences, resulting in a 13.2 percent rate of treatment failure (P = 0.058).

Sphincterotomy up to the dentate line provided a faster and definitive healing within the time limits of this study, but it was associated with a significant alteration in anal continence. In turn, sphincterotomy up to the fissure apex was free of significant disturbance of continence, but its healing effect was slower and it was prone to an insignificantly higher rate of treatment failure.