Choledocholithiasis is the presence of gallstones within the common bile duct (CBD). It is a complication of cholelithiasis and can cause biliary obstruction, jaundice, cholangitis, and pancreatitis. On ultrasound, CBD stones appear as hyperechoic foci within the duct lumen with posterior acoustic shadowing and upstream biliary dilation. Distal CBD stones near the ampulla of Vater may be obscured by overlying bowel gas, reducing ultrasound sensitivity. MRCP or endoscopic ultrasound are used when CBD stones are clinically suspected but not seen on transabdominal ultrasound.