Choledocholithiasis occurs when gallstones lodge in the bile ducts and bile can no longer flow, instead backing up into the liver. Most cases are symptomatic and require removal of the stones since ascending cholangitis (acute bacterial infection of the biliary tree) is a common complication with high morbidity/mortality.
Patients with choledocolithiasis usually present with biliary colic and obstructive jaundice, ascending cholangitis, and potentially acute pancreatitis (Hartung).
On ultrasound, look out for calculi in the gallbladder and/or CBD, and a dilated common bile duct. Any CBD wider than 5mm should raise suspicion, especially when paired with a suggestive history. However, with every decade of life past 50, the expected diameter increases by one millimeter. For example, a 60-year-old patient would be expected to have a CBD around 6mm, and a 70-year-old patient would be expected to have a CBD of 7mm.