5F sphincterotomes and 4F sphincterotomes are equivalent for the selective cannulation of the common bile duct.

Background: Cannulation of the common bile duct (CBD) is the first step in endoscopic retrograde cholangiopancreatography (ERCP). Cannulation difficulty is a known risk factor for post-ERCP complications and may be minimized by the use of a smaller caliber sphincterotome.

Objective: To compare the efficacy of CBD cannulation with a 4 F versus a 5 F sphincterotome.

Design: A randomized controlled trial, with concealed allocation and double-blinding.

Patients: Adult patients undergoing their first ERCP at a tertiary referral center.

Intervention: Patients were randomized to undergo CBD cannulation with either a 4 F or 5 F sphincterotome.

Main Outcome Measurements: Successful deep cannulation in <15 attempts was the primary outcome. Secondary outcomes included number of attempts/time to cannulation, incidence of complications within 24 hours, and overall cannulation success (including patients before and after crossover). Analysis was intention to treat and included standard descriptive and inferential methods.

Results: A total of 107 patients were randomized: 51 (4 F) versus 56 (5 F). The majority were female (71%) and white (92%). Baseline demographics, presenting symptoms, and laboratory values were similar between groups. Similar success in initial cannulation was observed: 84.3% (4 F) and 83.9% (5 F). No differences were noted in time to cannulation (5.12 min [SD, 4.8] for 4 F vs 4.46 min [SD, 4.13] for 5 F; p = NS), number of attempts to cannulation (6.2 [SD, 5.2] for 4 F vs 5.7 [SD, 4.9] for 5 F; p = NS), or complications. The overall cannulation success was 92.2% (4 F) and 92.9% (5 F).

Limitations: Premature termination of the trial resulted in decreased power.

Conclusions: There exists no significant difference in efficacy between 4 F and 5 F sphincterotomes. The choice of initial sphincterotome should be dictated by physician preference.