Preoperative enema for anal surgery: randomized clinical trial

Haemorrhoidal surgery and anal fistula surgery are two of the most common procedures in proctology. Currently, there is no definitive consensus on the need to administer a preoperative enema. The objective of this study was to evaluate the efficacy and benefits of preoperative enemas in anal surgical procedures.

Patients diagnosed with grade III or IV haemorrhoids and anal fistulas at the Taipei Medical University Shuang-Ho Hospital, Taiwan, between 2022 and 2023, were enrolled in a randomized clinical study comparing the use of preoperative enema (intervention) versus no preoperative enema (control). The primary outcome measures included postoperative visual analogue scale scores and analgesic usage from postoperative day 0 to day 7. Secondary outcomes of interest were postoperative complications, including surgical site infection, postoperative bleeding and urinary retention. Subgroup analyses were performed according to the type of procedure for the same outcomes.

A total of 266 patients were enrolled in this study, with 133 allocated to the enema group and 133 to the control group. No significant differences were observed in postoperative visual analogue scale scores, analgesic consumption and postoperative complications between the two groups. Subgroup analysis revealed that patients undergoing stapled haemorrhoidopexy and anal fistula surgery also showed no significant differences in postoperative visual analogue scale scores, analgesic consumption, and postoperative complications between the enema and control groups. However, in the subgroup of patients undergoing Milligan-Morgan haemorrhoidectomy, the mean(s.d.) visual analogue scale score was significantly higher in the control group than in the enema group on day 2 (5.69(2.14) versus 3.77(2.45), P = 0.021), day 3 (5.85(2.61) versus 3.92(2.73), P = 0.042) and day 4 (5.23(2.55) versus 3.42(2.18), P = 0.027).

Preoperative enema in anal surgery did not yield additional benefits or reduce complications when compared with patients who did not undergo enema before anal surgery. Based on the study findings, its use can be omitted in anal surgery, especially for patients undergoing stapled haemorrhoidopexy and anal fistula surgery.