Efficacy of abdominal drainage in perforated appendicitis: a retrospective single-center study using AAST grading and inverse probability treatment weighting analysis

BACKGROUND: While routine use of abdominal drainage in cases of perforated appendicitis is not generally recommended, there exists a paucity of evidence regarding the detailed stratification of its necessity based on varying degrees of intraoperatively detected abdominal contamination. This study aimed to assess the relationship between abdominal drainage and postoperative outcomes in patients with perforated appendicitis, categorized according to AAST severity grades. METHODS: This study retrospectively included 278 patients with perforated appendicitis who underwent laparoscopic surgery between January 2021 and December 2025. Patients were classified according to the American Association for the Surgery of Trauma (AAST) grading criteria into AAST grades 3&4 (126 patients) and AAST grade 5 (152 patients). The primary outcome measured was the occurrence of surgical complications within 30 days post-surgery. Inverse probability of treatment weighting (IPTW) was employed to control for confounding variables, and E-value analysis was conducted alongside multifactorial logistic regression to evaluate the relationship between drainage and outcomes. RESULTS: In patients with AAST grade 5 appendicitis, abdominal drainage did not significantly reduce the risk of intra-abdominal abscess (aOR = 1.60, 95% CI: 0.54-4.72, P = 0.396) and may be linked to an increased risk of overall surgical complications (aOR = 2.16, 95% CI: 0.88-5.28, P = 0.091). Multifactorial logistic regression analysis indicated that drainage was an independent risk factor for surgical complications (aOR = 2.42, 95% CI: 1.02-5.77, P = 0.045). The median length of hospital stay was significantly longer in the drainage group compared to the non-drainage group (5.0 days vs. 3.0 days), as were medical costs (CNY 16,100 vs. CNY 14,100), with both comparisons yielding P < 0.001. Among patients with AAST grades 3&4 appendicitis, no statistically significant differences were observed between the drainage and non-drainage groups regarding overall complications (15.4% vs. 7.0%, P = 0.236) or intra-abdominal abscess (11.5% vs. 3.0%, P = 0.102). Furthermore, in AAST grades 3&4 patients, drainage did not significantly influence the risk of overall complications, abdominal abscesses, or other secondary outcomes (all P > 0.05). CONCLUSION: For AAST grade 5 perforated appendicitis, routine drainage fails to prevent complications and may increase risks, recovery time, and costs. Likewise, no significant benefit was observed in grades 3&4. Therefore, routine drain use is not recommended, favoring individualized intraoperative decision-making.