Botulinum toxin reduces anal spasm but has no effect on pain after haemorrhoidectomy

Abstract Objective Pain following haemorrhoidectomy is due to a combination of factors including spasm of the internal sphincter, an open wound and local infection. In this study, we investigated the effect of botulinum toxin on postoperative pain following Milligan–Morgan haemorrhoidectomy. Method A prospective randomized controlled trial was conducted in 32 patients undergoing haemorrhoidectomy. Routine postoperative care included metronidazole and bupivacaine. Patients were also given an inter‐sphincteric injection of either placebo or botulinum toxin (150 units). Maximal resting pressure (MRP) and maximal squeeze pressure (MSP) were measured postoperatively. A linear analogue score was used to assess postoperative pain. The sample size calculation was calculated to show one standard deviation difference between groups. The primary endpoint was reduction in postoperative pain. Results The MRP was significantly lower in the botulinum toxin group (mean 50.5 mmHg; 95% CI 39.77–61.23) compared with the placebo group (mean 64.94 mmHg; 95% CI 55.65–74.22) ( P = 0.04) at week 6. At week 12 there was no significant difference in MRP between the two groups. In contrast MSP was significantly lower in the botulinum toxin group at weeks 6 and 12 (mean 87.1 mmHg; 95% CI 66.9–107.1) compared with the placebo group (mean 185.8 mmHg; 95% CI 134.2–237.4) at week 12 ( P = 0.0014). There was no significant effect on overall or maximal pain scores. Median time for return to normal activities was not significantly different between groups. Conclusion Botulinum toxin reduces anal spasm but has no significant effect on postoperative pain.