Prophylactic abdominal drainage versus no drainage after laparoscopic appendectomy for perforated acute appendicitis: a multicenter propensity score-weighted analysis.

BACKGROUND

While laparoscopic appendectomy is the standard of care for acute appendicitis, the clinical utility of prophylactic abdominal drainage in perforated acute appendicitis remains controversial. Previous observational studies often lacked granular perioperative covariate adjustment and control for institutional clustering effects. We aimed to determine the association between prophylactic drainage and intra-abdominal abscess (IAA) formation using a unified mixed-effects framework.

METHODS

The Drainage of Laparoscopic Appendectomy for Perforated Appendicitis (DLAP) study was a retrospective multicenter cohort study involving 21 institutions in Japan. Patients undergoing emergency laparoscopic appendectomy for perforated acute appendicitis between 2015 and 2023 were evaluated. Confounder adjustment across 16 baseline covariates was performed using Overlap Weighting (OW). Secondary sensitivity analyses utilized Inverse Probability of Treatment Weighting (IPTW) and 1:1 Propensity Score Matching (PSM). Institutional clustering was accounted for using generalized linear mixed-effects models (GLMM) with participating centers as random intercepts across the primary and sensitivity analyses. Predictive importance of variables for 30-day postoperative IAA was explored using a Random Forest classifier.

RESULTS

Among 671 included patients, 452 (67.4%) received a prophylactic drain and 219 (32.6%) did not. In the primary OW-GLMM analysis, prophylactic drainage was not significantly associated with a lower risk of 30-day postoperative IAA formation (adjusted Odds Ratio [OR] = 1.00; 95% Confidence Interval [CI] 0.35-2.87; P = 0.995). Similar findings were observed in the sensitivity IPTW (adjusted OR = 1.52; P = 0.348) and PSM cohorts (adjusted OR = 1.00; P = 0.991). In contrast, drain placement was associated with a longer postoperative hospital stay (mean difference = 2.04 days; P = 0.024) and higher total hospitalization expenditures (mean difference = 192,937 JPY; [1,286 USD] P = 0.025). Exploratory subgroup analysis suggested an interaction between drain placement and intraoperative washing volume (P for interaction = 0.034). In the Random Forest analysis, intraoperative washing volume showed the highest predictive importance for IAA development (Mean Decrease Gini = 45.2), whereas prophylactic drainage ranked near the bottom of the evaluated clinical variables (1.2).

CONCLUSIONS

Prophylactic abdominal drainage after laparoscopic appendectomy for perforated acute appendicitis was not associated with a lower risk of postoperative intra-abdominal abscess formation and was associated with longer postoperative hospitalization and higher financial expenditures. Intraoperative washing volume was an important predictor of abscess development. These findings suggest that routine drain placement may not provide measurable clinical benefit in this setting.