Angsuwatcharakon 2012.

Methods	Single‐centre RCT with 1 expert endoscopist in Thailand. Trainees were involved prior to randomisation
Participants	Consecutive patients aged > 15 yrs with native papilla undergoing ERCP in whom cannulation of the CBD failed with conventional contrast‐assisted cannulation techniques. Excluded patients with altered anatomy of the stomach, ampulla, obstructive PD, and recent pancreatitis. Difficult cannulation was defined as the inability to cannulate the CBD after 5 minutes by trainees followed by 10 minutes by the expert endoscopist (total of 15 minutes)
Interventions	PGW placement (double guidewire technique) vs precut sphincterotomy (freehand fistulotomy technique). 1. PGW: A catheter was pre‐inserted with a 0.035" guidewire (Jagwire; Boston Scientific) to facilitate PD cannulation. No contrast was injected into the PD. After the first guidewire was inserted and left in the PD, the catheter was exchanged and loaded with the second guidewire. The catheter was reinserted into the scope via the same working channel along the first guidewire. The direction of biliary cannulation was aimed to 10‐11 o’clock position, with a left, upward relation to the first guidewire. Successful cannulation was achieved after the second guidewire was left and lateral to the first one. This was confirmed by either a positive bile aspiration or a successful cholangiogram. 2. Precut sphincterotomy: A MicroKnife XL (Boston Scientific) was used to dissect the ampullary mucosa in a freehand fistulotomy fashion. PD stent was not used for prophylaxis of PEP
Outcomes	Biliary cannulation success, cannulation time, post‐ERCP serum amylase level, and complications including PEP, immediate bleeding, delayed bleeding, perforation, and cholangitis
Notes	1.'Cross‐over' design: If biliary cannulation was not achieved by the assigned technique in another 10 minutes, the other method was performed. 6 participants cross over from PGW to precut (3 inability to cannulate the PD, 3 after achieving deep PD cannulation). 4 participants in the precut group cross over to the PGW group. 2. Diagnosis for PEP was based on the consensus criteria (pancreatitis‐type abdominal pain and a serum amylase level over 3 times the upper normal limit that lasted more than 24 hours after the procedure) or pain and evidence of acute pancreatitis by computed tomography scan or magnetic resonance imaging of the abdomen. Hyperamylasaemia without abdominal pain was not recorded as PEP. Severity of pancreatitis was based on the consensus criteria (Cotton 1991)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Unclear how the randomisation list was generated. "Eligible patients were randomised by a simple randomised technique that was generated outside of the endoscopy unit"
Allocation concealment (selection bias)	Low risk	"The ERCP team did not know the sequence of randomisation until they declared such patients to be a case of truly difficult cannulation, and then the enveloped code was broken"
Blinding of participants and personnel (performance bias) All outcomes	High risk	Endoscopists could not be blinded. Unclear whether participants or personnel were blinded
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Unclear whether outcome assessors were blinded. All participants were admitted to the hospital for at least 24 hours to observe for post‐ERCP complications. Serum amylase concentration was measured at 24 hours after ERCP regardless of the presence or absence of abdominal pain. As a result, participants may be more likely to undergo laboratory and radiological evaluation as opposed to being discharged home following ERCP. If outcome assessors were not blinded, this could lead to differential detection bias
Incomplete outcome data (attrition bias) All outcomes	Low risk	Follow‐up appeared to be complete
Selective reporting (reporting bias)	Low risk	Reported all planned outcomes
Other bias	Low risk	No other risk of bias