Early precut is useful for difficult bile duct cannulation, particularly in cases with long oral protrusion

Figure 1 Flow chart of the inclusion process. ERCP: Endoscopic retrograde cholangiopancreatography; B-I: Billroth I reconstruction.

Figure 2 Flow chart of biliary cannulation. ACT: Advanced cannulation technique; SCT: Standard cannulation techniques; ERCP: Endoscopic retrograde cholangiopancreatography; EUS-HGS: Endoscopic ultrasonography-guided hepaticogastrostomy; EUS-rendezvous: Endoscopic ultrasound-guided rendezvous technique; PTBD: Percutaneous transhepatic biliary drainage.

Figure 3 Stepwise endoscopic images of early precut needle knife fistulotomy in a case with a large oral protrusion. A: Papilla with a long oral protrusion (oral protrusion-L); the incision line is marked at the apex of the protrusion prior to precutting; B: The initial incision is made using a needle knife, limited to the oral protrusion only, avoiding the papillary orifice characteristic of needle knife fistulotomy; C: Exposure of the sphincter of the Oddi muscle layer (highlighted with a blue circle). The extended oral protrusion allows for a wide incision plane, facilitating clear visualization of the muscle layer; D: Identification of the artificially created bile duct opening after further dissection (blue arrow); E: Successful bile duct cannulation with a guidewire through the exposed opening.