Double-blind randomised controlled trial of effect of metronidazole on pain after day-case haemorrhoidectomy

Background Haemorrhoidectomy is commonly an inpatient procedure because patients and doctors worry about postoperative pain. Day-case haemorrhoidectomy (DCH) is possible if patient anxiety is addressed and postoperative pain and bower function are managed. Pain sometimes increases a few days after haemorrhoidectomy, possibly because of secondary infection. We studied the effect of metronidazole on pain after DCH, Methods We randomly assigned 40 consecutive patients admitted for DCH metronidazole 400 mg (n=20) or placebo (n=20) three times daily, both for 7 days. All patients received lactulose from 2 days before surgery for 2 weeks. Diathermy DCH was performed without pedicle ligature or anal-canal dressing, and a diclofenac suppository was administered at the end of the procedure. Patients were discharged on the same day with diclofenac, 0.2% glyceryl-trinitrate ointment, lactulose, a telephone number to call for queries in emergencies, and an outpatient appointment. Patients took paracetamol or Co-dydramol (dihydrocodeine and paracetamol) as required; they completed linear analogue charts every day and completed questionnaires on satisfaction at 1 and 6 weeks. Findings 34 patients had all three major piles excised, of whom seven had additional division and reconstruction of the posterior skin bridge. Overall, both groups of patients experienced less pain than expected, except on days 3 and 4. Patients in the metronidazole group had significantly less pain than those in the placebo group on days 5, 6, and 7 (p=0.004, p=0.02, and p=0.006). Median time to return to work or normal activity was 15 days (range 12-28) in the metronidazole group and 18 days (7-34) in the placebo group (p=0.009). The patient satisfaction score was higher in the metronidazole group than in the placebo group at 1 week (p=0.005). Interpretation Prophylactic metronidazole in diathermy DCH suppressed secondary pain around days 5-7 and increased patient satisfaction and earlier return to work.