Liver transplant (LT) recipients frequently require biliary interventions to manage post-transplant complications and remain at increased risk for infectious adverse events. This study aimed (1) to evaluate the prevalence of infectious complications following biliary drainage in LT recipients and to identify associated clinical and intraprocedural risk factors, and (2) to describe the biliary and intestinal microbiological profile, including bile culture results and rectal colonization patterns.

We conducted a retrospective single-centre study including all adult patients who underwent LT at our institution between January 2017 and December 2022. Among these, we selected those who underwent Endoscopic Retrograde Cholangiopancreatography (ERCP), Double-Balloon Enteroscope–assisted ERCP (DBE-ERCP), or Percutaneous Transhepatic Cholangiography (PTC) within 24 months from transplantation. We collected clinical, microbiological and interventional data, including indication for biliary drainage, procedure type, endoscopic interventions (sphincterotomy, balloon dilation, stent placement or removal, endoscopic device configuration), bile culture and rectal swab results, and antimicrobial exposure. Clinically significant infectious events occurring within 30 days after the procedure including cholangitis, primary bloodstream infection, intra-abdominal infection, surgical site infection, liver abscess, and acute bacterial skin and skin structure infection, were recorded. Continuous variables were summarised as mean (SD) or median (IQR), and categorical variables as counts and percentages. Associations with infectious events were assessed by univariable logistic regression, reporting unadjusted odds ratios (OR) with 95% confidence intervals, while group comparisons used chi-square or Fisher’s exact tests as appropriate. A p-value < 0.05 was considered statistically significant. Analyses were performed using R (version 4.5.1).

Seventy-one LT recipients (mean age 55.5 ± 9.9 years, 74.6% males) underwent 238 biliary procedures (81.5% ERCP, 17.6% PTC, 0.8% DBE-ERCP). Indications included anastomotic strictures (58.8%), stent removal (18.9%), bile leakage (8.8%), biliary fistula (6.3%), bile duct stones (5.9%), and procedures performed to treat active biliary infection (26.9%). Bile cultures were obtained in 110 procedures (46.2%) and showed a high diagnostic yield, with 81.8% positivity. Enterobacterales accounted for the majority of isolates (85.6%), followed by Enterococcus faecium (14.4%). Multidrug-resistant organisms were identified in 22.2% of positive cultures. Rectal swabs performed within 90 days before the procedure were available for 147 procedures (61.8%) and were positive in 41.5% of cases. Infections following biliary procedures were found in 44 out of 238 procedures (18.5%), accounting for a total of 49 infectious episodes, as some patients developed more than one event during the follow-up period. Infectious events were significantly associated with LT for primary or secondary sclerosing cholangitis (OR 5.97, 95%CI 1.72–21.7; p = 0.0046), with early biliary complications after LT such as leaks or strictures (OR 2.03, 95%CI 1.05–3.96; p = 0.036), and with younger age at LT, assessed as a per-year decrease in age (OR 0.96, 95%CI 0.93–0.99; p = 0.0347). On the contrary, a significantly lower risk of infectious was observed in case of biliary re-intervention leading to stent removal (OR 0.27; 95%CI 0.06–0.77; p = 0.0329;) and when ERCP was conduct using duodenoscope equipped with a single-use tip (OR 0.35, 95%CI 0.18–0.64, p = 0.002). The rate of infectious complications following biliary drainage was not affect by sphincterotomy or stent placement, as well by antibiotic exposure, either prophylactic or therapeutic.

In LT recipients undergoing biliary procedures, primary or secondary sclerosing cholangitis at LT and early post-LT biliary complications are linked to a higher risk of clinically relevant infections after drainage. The protective effect of single-use duodenoscope tips and the high diagnostic yield of bile cultures for multidrug-resistant pathogens highlight the role of procedural optimization in preventing infections. These results support an integrated approach in which microbiological sampling and endoscopic or radiologic interventions guide personalized management. Prospective studies are needed to define optimal antimicrobial and biliary drainage strategies in high-risk patients.