Multicenter study of lumen-apposing metal stents with or without pigtail in endoscopic ultrasound-guided biliary drainage for malignant obstruction-BAMPI TRIAL: an open-label, randomized controlled trial protocol - Garcia-Sumalla, A; Loras, C; Sanchiz, V; Spanish Working Group on Endoscopic Ultrasound Guided Biliary Drainage (Trials, 2022)