A 65 year old man underwent elective cholecystectomy yesterday for chronic cholecystitis. He reports abdominal pain and is found to have increasing serum transaminases and bilirubin.
Anterior images from hepatobiliary (HIDA) study performed after intravenous injection of Tc99m Mebrofenin demonstrate normal clearance of radiotracer activity from the blood pool, by approximately 7 minutes after injection. However there is no activity within the bile ducts by 60 minutes.
A repeat anterior image at 2 hours post injection shows similar findings:
The HIDA study is diagnostic of high-grade biliary obstruction. In the post-cholecystectomy setting, this maybe caused by a retained gallstone in the common bile duct or inadvertent ligation of the common bile duct.
In this case, the patient underwent ERCP which demonstrated a common bile duct stone (arrow). The stone was removed with a balloon sweep and a sphincterotomy was performed.
Common bile duct stones (choledocholithiasis) may infrequently be seen as echogenic foci on ultrasound, though visualization of the distal common bile duct is often limited by overlying bowel gas. Hyperdense or calcified gallstones can be identified on CT, though a certain percentage of stones are isodense to bile (around 30%) and occult. Soto JA, et al. AJR 2000;175:1127-34.
MRCP is considered the gold standard for noninvasive visualization of common bile duct stones, seen as hypointense filling defects on T2 weighted images. Note however that small stones (<6 mm) may still be missed on MRCP, though this is likely becoming less common as image quality improves. Zidi SH, et al. Gut 1999;44:118-22. Chen W, et al. World j Gastroenterol 2015;21:3351-60.
Take a look at these axial T2 images from another patient with a distal common bile duct stone (arrow):
The same filling defect is seen on a maximum intensity projection (MIP) image from the heavily T2-weighted MRCP images:
