Impact of guidewire caliber on biliary cannulation outcomes: a prospective randomized comparison of 0.025-inch and 0.035-inch guidewires

Background and aim Guidewire-assisted biliary cannulation is the standard technique for endoscopic retrograde cholangiopancreatography (ERCP). Whether guidewire caliber influences cannulation success or post-ERCP pancreatitis (PEP) remains uncertain. We evaluated whether the 0.025-inch guidewire is non-inferior to the 0.035-inch guidewire for primary biliary cannulation of the intact papilla.Patients and methods In this prospective, single-blind, randomized non-inferiority trial, 130 patients with an intact papilla were randomized 1:1 to wire-guided cannulation with a 0.025-inch or 0.035-inch guidewire. The primary outcome was successful biliary cannulation achieved before the ESGE/SADE criteria for difficult cannulation were met, a stricter endpoint than final cannulation success, which was recorded separately. A planned subgroup analysis compared outcomes by endoscopist experience.Results Primary cannulation success was 47.7% (31/65) with the 0.025-inch wire and 43.1% (28/65) with the 0.035-inch wire, a risk difference of +4.6% (95% CI −12.2 to +21.1; p = 0.73), confirming non-inferiority. Final cannulation success was 96.9% (63/65) in both groups. Cannulation time (335 vs. 420 s; p = 0.74), PEP rate (9.2% vs. 16.9%; p = 0.30), and failed cannulation (3.1% vs. 3.1%) were comparable. Experienced endoscopists achieved higher primary cannulation success with the 0.025-inch wire than fellows (67.9% vs. 32.4%; p = 0.006) and shorter cannulation times (178 vs. 889 s; p = 0.0002), but neither wire was superior within either experience stratum and the wire-by-experience interaction was not significant (p = 0.16).Conclusions The 0.025-inch guidewire is non-inferior to the 0.035-inch guidewire for primary biliary cannulation. Operator experience, not guidewire caliber, was the dominant determinant of primary cannulation success. A specific advantage of the thinner wire in experienced hands is suggested by our data but not established.