Introduction

Malignant biliary obstruction (MBO) often necessitates endoscopic retrograde cholangiopancreatography (ERCP) for biliary drainage. Although ERCP is standard treatment, post-procedural infections such as cholangitis and cholecystitis remain clinically important. Current guidelines recommend prophylactic antibiotics only for high-risk cases. Clinically, MBO is categorized into distal malignant biliary obstruction (DMBO) and hilar malignant biliary obstruction (HMBO), depending on whether the obstruction involves the extrahepatic duct or the intrahepatic duct/hilar confluence. While several studies have supported the use of prophylactic antibiotics in HMBO, evidence remains limited for DMBO. This study aimed to evaluate the effect of prophylactic antibiotics on post-ERCP infectious complications in DMBO.

Aims & Methods

We retrospectively reviewed patients who underwent initial ERCP with stent placement for DMBO at five Japanese centers between January 2020 and September 2024. Patients were grouped based on the use or non-use of prophylactic antibiotics for ERCP. Propensity score matching (1:1) was performed using clinically relevant covariates. In addition, a sensitivity analysis was conducted via multivariable logistic regression on the before matched data to further assess the robustness of the findings. The primary outcome was the incidence of infectious complications (cholangitis or cholecystitis) within five days of ERCP.

Results

A total of 508 patients (304 in the antibiotic group, 204 in the non-antibiotic group) were included in the study. After PSM, 165 patients were selected for each group. Characteristics of the antibiotic vs. non-antibiotic groups included: median age 74 years in both groups; sex 92 (55.8%) males vs. 94 (57.0%) males; pancreatic cancer 129 (77.2%) cases vs. 133 (79.6%) cases; plastic stents 72 (43.6%) cases vs. 69 (41.8%) cases.
In the matched population, the incidence of overall infectious complications (cholangitis or cholecystitis) was significantly lower in the prophylactic antibiotic group than in the non-antibiotic group (3.6% vs. 10.3%; risk difference (RD), 6.7%; p=0.029), corresponding to a number needed to treat (NNT) of 14.9. No significant difference was observed in the rate of post-ERCP pancreatitis: 10 patients (6.1%) in the non-antibiotic group and 16 patients (9.7%) in the antibiotic group (p = 0.307). Sensitivity analysis using multivariable logistic regression confirmed that absence of prophylactic antibiotics was independently associated with a higher risk of infectious complications (odds ratio: 2.45, 95% confidence interval: 1.22–4.92).

Conclusion

Prophylactic antibiotics significantly reduce post-ERCP infectious complications in patients with DMBO.