Abdominal drainage to prevent intraperitoneal abscess after appendectomy for complicated appendicitis.

Rationale: This is the third update of a Cochrane review first published in 2015 and last updated in 2021. Appendectomy, the surgical removal of the appendix, is performed primarily for acute appendicitis. People who undergo appendectomy for complicated appendicitis, defined as gangrenous or perforated appendicitis, are more likely to suffer postoperative complications in comparison to uncomplicated appendicitis. The routine use of abdominal drainage to reduce postoperative complications after appendectomy for complicated appendicitis is controversial.

Objectives: To evaluate the benefits and harms of abdominal drainage in reducing intraperitoneal abscess after appendectomy (irrespective of open or laparoscopic) for complicated appendicitis; to compare the effects of different types of surgical drains; and to evaluate the optimal time for drain removal.

Search methods: We searched CENTRAL, MEDLINE, Embase, two other databases, and five trials registers, together with reference checking, citation searching, and contact with study authors, to identify studies for inclusion in the review. The latest search date was 12 October 2023.

Eligibility criteria: We included randomised controlled trials (RCTs) and quasi-RCTs in people with complicated appendicitis comparing (1) use of drain versus no drain, (2) open drain versus closed drain, or (3) different schedules for drain removal. We excluded studies in which not all participants received antibiotics after appendectomy.

Outcomes: Our critical outcome was intraperitoneal abscess. Important outcomes were wound infection, morbidity, mortality, and hospital stay.

Risk of bias: We used the Cochrane RoB 1 tool to assess the risk of bias in RCTs and quasi-RCTs.

Synthesis methods: We synthesised the results for each outcome in a meta-analysis using the random-effects model, except for the Peto odds ratio, which only has a fixed-effect model. We planned to use the Synthesis Without Meta-analysis (SWiM) approach to report studies when it was not possible to undertake a meta-analysis of effect estimates. We used GRADE to assess the certainty of evidence for each outcome.

Included studies: We included eight studies (five RCTs and three quasi-RCTs) with a total of 739 paediatric and adult participants, of which 370 participants were randomised to the drainage group and 369 participants to the no-drainage group. The studies were conducted in North America, Asia, and Africa and published between 1973 and 2023. The majority of participants had perforated appendicitis with local or general peritonitis. All participants received antibiotic regimens after open or laparoscopic appendectomy. All studies were at overall high risk of bias.

Synthesis of results: Use of drain versus no drain We assessed the certainty of the evidence for 30-day mortality as moderate due to imprecision. We assessed the certainty of the evidence for all other outcomes as very low, downgraded mainly due to high risk of bias, inconsistency, and imprecision. The evidence is very uncertain regarding the effects of abdominal drainage versus no drainage on intraperitoneal abscess at 30 days (risk ratio (RR) 1.08, 95% confidence interval (CI) 0.55 to 2.12; 7 studies, 671 participants; very low-certainty evidence), wound infection at 30 days (RR 1.76, 95% CI 0.89 to 3.45; 7 studies, 696 participants), and morbidity at 30 days (RR 1.84, 95% CI 0.14 to 24.50; 2 studies, 124 participants) in paediatric and adult participants undergoing open or laparoscopic appendectomy for complicated appendicitis. Approximately 113 (57 to 221 participants) out of 1000 participants in the drainage group developed intraperitoneal abscess, compared with 104 out of 1000 participants in the no-drainage group. There were seven deaths in the drainage group (N = 291) compared with one in the no-drainage group (N = 290); abdominal drainage probably increases the risk of 30-day mortality (Peto odds ratio 4.88, 95% CI 1.18 to 20.09; 6 studies, 581 participants; moderate-certainty evidence) in paediatric and adult participants undergoing open appendectomy for complicated appendicitis. Abdominal drainage may increase hospital stay by 1.58 days (95% CI 0.86 to 2.31; 5 studies, 516 participants; very low-certainty evidence) in paediatric and adult participants undergoing open or laparoscopic appendectomy for complicated appendicitis, but the evidence is very uncertain. Open drain versus closed drain No studies compared open drain versus closed drain for complicated appendicitis. Early versus late drain removal No studies compared early versus late drain removal for complicated appendicitis.

Authors' conclusions: The evidence is very uncertain whether abdominal drainage prevents intraperitoneal abscess, wound infection, or morbidity in paediatric and adult participants undergoing open or laparoscopic appendectomy for complicated appendicitis. Abdominal drainage may increase hospital stay in paediatric and adult participants undergoing open or laparoscopic appendectomy for complicated appendicitis, but the evidence is very uncertain. Consequently, there is no evidence for any clinical improvement with the use of abdominal drainage in people undergoing open or laparoscopic appendectomy for complicated appendicitis. The increased risk of mortality with drainage comes from eight deaths observed in paediatric and adult participants undergoing open appendectomy for complicated appendicitis. Larger studies are needed to more reliably determine the effects of drainage on mortality outcomes.

Funding: This Cochrane review was funded by the National Natural Science Foundation of China (Grant No. 81701950, 82172135), Natural Science Foundation of Chongqing (Grant No. CSTB2022NSCQ-MSX0058, cstc2021jcyj-msxmX0294), Medical Research Projects of Chongqing (Grant No. 2018MSXM132, 2023ZDXM003, 2024jstg028), and the Kuanren Talents Program of the Second Affiliated Hospital of Chongqing Medical University.

Registration: Registration: not available. Protocol and previous versions available via doi.org/10.1002/14651858.CD010168, doi.org/10.1002/14651858.CD010168.pub2, doi.org/10.1002/14651858.CD010168.pub3, and doi.org/10.1002/14651858.CD010168.pub4.