Efficacy and safety of methylene blue for postoperative pain of haemorrhoids: a systematic review and meta-analysis

Pain is a common complication after haemorrhoid surgery. In addition to anaesthetic methods, surgical techniques and postoperative interventions, surgeons also use intraoperative adjuncts to alleviate postoperative pain. This study aims to evaluate the effectiveness and safety of methylene blue in reducing postoperative pain in haemorrhoid patients. A search was conducted in PubMed, Embase, Cochrane Library and Web of Science for randomized controlled trials (RCTs) up until 9 December 2024, involving methylene blue use for pain relief after haemorrhoid surgery. Two reviewers independently assessed the study eligibility, extracted data and evaluated the risk of bias. Data analysis was performed using Stata 18 software. The primary outcome was the visual analogue scale (VAS) pain scores at different time points within 14 days postoperatively. Secondary outcomes included the number of patients requiring analgesics and the occurrence of complications. 358 articles were retrieved and six studies involving 598 patients were included after screening. Compared with the control group, the use of methylene blue reduced pain within 12 h postoperatively(WMD −1.582, 95% CI −2.834 to −0.330, <i>p</i> = .013), as well as on day 2 (WMD −1.441, 95% CI − 1.874 to −1.008, <i>p</i> &lt; .0001), day 3 (WMD −0.975, 95% CI −1.309 to −0.641, <i>p</i> &lt; .0001), day 5(WMD −0.786, 95% CI −1.094 to −0.478, <i>p</i> = .028) and day 7 (WMD −0.679, 95% CI −1.257 to −0.101, <i>p</i> = .021), decreased the number of patients using analgesics(RR 0.293, 95% CI 0.203 to 0.422, <i>p</i> &lt; .0001) and did not increase the incidence of complications(RR 0.65, 95% CI 0.39–1.10, <i>p</i> = .111) such as urinary retention, secondary haemorrhage, pruritus, temporary incontinence, wound infection, or local skin reactions. This study shows that methylene blue can reduce postoperative pain, decrease analgesic use and does not increase complications after haemorrhoid surgery. Methylene blue can alleviate pain within 12 h postoperatively, as well as on days 2, 3, 5, 7 and reduce the patients’ need for analgesics.Methylene blue does not cause urinary retention, nor does it lead to secondary haemorrhage, pruritus, temporary urinary incontinence, wound infection, or local skin reactions.It is recommended to develop detailed methylene blue usage guidelines and create specialized methylene blue products for the treatment of colorectal diseases to ensure that doctors can use the medication compliantly and effectively. Methylene blue can alleviate pain within 12 h postoperatively, as well as on days 2, 3, 5, 7 and reduce the patients’ need for analgesics. Methylene blue does not cause urinary retention, nor does it lead to secondary haemorrhage, pruritus, temporary urinary incontinence, wound infection, or local skin reactions. It is recommended to develop detailed methylene blue usage guidelines and create specialized methylene blue products for the treatment of colorectal diseases to ensure that doctors can use the medication compliantly and effectively.