Intraductal ultrasonography (IDUS) is one of the most useful diagnostic tools for various extrahepatic biliary diseases. However, conventional IDUS has some limitations in providing accurate cross-sectional imaging of the bile duct in patients with extensive pneumobilia. Using a balloon-sheathed catheter, the US system (balloon-sheathed IDUS) can overcome these limitations. Sixteen patients underwent balloon-sheathed IDUS during endoscopic retrograde cholangiography. The balloon-sheathed IDUS was inserted via a transpapillary route when visualization of the bile duct with conventional IDUS was distorted by extensive pneumobilia. The patient group had a mean age of 65.5 years, and 56.3% (9/16) were male. The balloon-sheathed IDUS permitted successful visualization of the bile duct in all patients, regardless of the extent of pneumobilia. Using this system, remnant common bile duct stones were detected in five patients (31.3%), and cholangiocarcinoma was detected in one patient (6.3%). The balloon-sheath IDUS aided in stone sweeping. No significant complications, including bleeding, perforation, or pancreatitis, occurred in any of the patients. The balloon-sheathed catheter US system was useful and safe for biliary IDUS in patients with extensive pneumobilia.