Incidence and risk factors for Acute cholecystitis (AC) following ERCP with self-expandable metal stents (SEMS) for distal malignant biliary obstruction (DMBO) have been scarcely explored in retrospective studies.

Between Feb-2024 and Apr-2025, all consecutive candidates to ERCP with a partially covered SEMS were enrolled in a single-centre prospective study (ClinicalTrials.gov NCT04813055). Two independent endoscopists blindly assessed morphological risk factors at EUS and ERCP. Clinical outcomes were evaluated by one independent assessor during admission and every 60 days. Multivariate logistic regression for Post-ERCP AC (PEC) was performed.

130 patients with DMBO were included (median age 71 [IQR 62-77], pancreatic adenocarcinoma 84.6%). At EUS, cystic duct (CD) was infiltrated in 16.9% and closer than 10 mm from the neoplasia in 14.6% of cases. At ERCP the SEMS covered the CD in 38.3% of the procedures. 

Median follow-up was 119 [54-204] days. Ten (7.7%) patients experienced post-ERCP pancreatitis whereas twelve (9.2%) experienced PEC, after a median time of 5.5 [5-51] days.

At multivariate logistic regression, the only independent predictor of PEC was a high-risk CD location (namely infiltrated or < 10mm from the neoplastic stenosis (OR [95% CI]= 5.2 [1.5-18.3]

In the context of SEMS placement for DMBO, PEC is relatively more frequent than post-ERCP pancreatitis. EUS ahead of ERCP can reliably predict this event as a high-risk CD location seems to independently predict this event.