Choledocholithiasis

Pathogenesis:

One of the most common causes of biliary disease, such as obstruction and infection.
Stones usually form in the gallbladder and may reach the common bile duct by passing through the cystic duct or by fistulous erosion through the gallbladder wall.
Many common duct stones lodge distally in the intrapancreatic portion of the common duct, producing pain, jaundice and elevated Liver Function Test (LFT).
Stones can form primarily within the ducts, usually due to bacterial deconjugation of bilirubin. This can also occur after cholecystectomy.

Radiographic findings:

Cholangiography: single or multiple filling defects in the opacified biliary tree that move freely and change location with alterations in patient position.

            Visible gallstones after injection           Visible occlusion by gallstones
  of contrast.                                                  after injection of contrast.

U/S: can image about 90% of proximal duct and 70% of distal duct stones.
Most common duct stones are echogenic structures that cast an acoustic shadow (about 10% do not shadow on U/S).

Transverse US image demonstrates
echogenic, shadowing stones in CBD.

CT: may demonstrate characteristic target and crescent signs.

CT shows distal CBD stone (arrow) and
surrounding dilated CBD causing the target sign.

Figures: Two different patients with multiple large stones within the extra hepatic bile ducts. Note multiple filling defects from CBD stones in (A)ERCP and (B)PTHC.

A B