Internal anal sphincter function following lateral internal sphincterotomy for anal fissure: a long-term manometric study

BACKGROUND: Anal fissure is a common and painful disorder. Its relation to hypertonic anal sphincter is controversial. The most common surgical treatment of chronic anal fissure is lateral internal sphincterotomy. OBJECTIVE: The aim of this study was to evaluate long-term manometric results of sphincter healing following lateral internal sphincterotomy. PATIENTS AND METHODS: Between 2000 and 2003, 50 patients with anal fissure were included in this study and underwent sphincterotomy; 12 healthy patients served as controls. All patients with anal fissure underwent manometric evaluation using a 6-channel perfusion catheter. All patients were examined 1 month before surgery and 1, 3, 6, and 12 months following surgery. The control group had 3 manometric evaluations 6 months apart. RESULTS: The mean basal resting pressure before surgery was 138 +/- 28 mm Hg. One month after surgery, the pressure dropped to 86 +/- 15 mm Hg (P < 0.0001) and gradually rose to a plateau at 12 months (110 +/- 18 mm Hg, P < 0.0001). At 12 months, the manometric pressure was significantly lower than the baseline (P < 0.0001). However, manometric measurements in the fissure group were still significantly higher than in the control group (110 +/- 18 versus 73 +/- 4.8 mm Hg, P < 0.0001). All patients were free of symptoms at the 12-month follow-up. CONCLUSION: Lateral internal sphincterotomy caused a significant decline in the resting anal pressure. During the first year following surgery, the tone of the internal anal sphincter gradually increased, indicating recovery, but still remained significantly lower than before surgery. However, postoperative resting pressures were higher than those in the control, and no patient suffered any permanent problems with incontinence, so this decrease may not be clinically significant.