<b><i>Introduction:</i></b> Gallbladder carcinoma is often difficult to distinguish from benign gallbladder diseases. While the diagnostic accuracy of endoscopic transpapillary gallbladder drainage (ETGD) has been reported, these results were obtained retrospectively. This prospective study aimed to evaluate the cytological diagnostic accuracy of ETGD in patients with gallbladder disease. <b><i>Methods:</i></b> This single-arm prospective clinical trial included a total of 35 patients scheduled to undergo ETGD between March 2017 and September 2019. A 5F pigtail nasobiliary drainage tube was inserted into the gallbladder, and bile was collected over 5 times; if ETGD failed, a drainage tube was placed into the bile duct. The endpoints were, first, the cytological diagnostic accuracy of ETGD and, second, technical success rates and adverse events. <b><i>Results:</i></b> Of the 35 patients, 19 were finally diagnosed with gallbladder cancer. The success rate of ETGD tube insertion was 85.7%, and the morphological pattern of the cystic duct with the angle down and located on the right side had a significantly lower success rate for ETGD than that of other cystic duct patterns (odds ratio, 13.5; 95% confidence interval, 1.7–143.7; <i>p</i> = 0.02). Cytological samples were collected 5 times on median. The sensitivity, specificity, and accuracy in all patients were 78.9%, 100%, and 88.6%, respectively, while those in 30 patients with successful ETGD were 87.5%, 100%, and 93.3%, respectively. Adverse events occurred in 3 patients: mild pancreatitis in 1 patient and obstructive jaundice in 2 patients; all complications were resolved with conservative therapy. <b><i>Discussion/Conclusions:</i></b> Cytology using an ETGD tube is useful in differentiating benign and malignant gallbladder diseases (Clinical Trial Registry No. UMIN000026929).
The rendezvous technique involving insertion of a guidewire in a percutaneous transhepatic gallbladder drainage tube for biliary access in a case of difficult biliary cannulation
