Ultrasound Detection of Choledocholithiasis: Direct and Indirect Signs

Direct Signs

The direct sign of a stone in the bile ducts is an echogenic formation in the lumen with an acoustic shadow behind it. According to the literature, echogenic ovoid structures in the distal parts of intrahepatic ducts are considered stones or sludge clots (Textbook of Diagnostic Sonography, 9th ed., 2023).

In intrahepatic stones, a pattern of bright echogenic foci with a linear/branching configuration along the portal triads, with a reverberation artifact or 'dirty' acoustic shadow, is characteristic. These foci are most commonly located in intrahepatic bile ducts but may involve extrahepatic ducts and the gallbladder (Diagnostic Ultrasound: Abdomen & Pelvis, 2nd ed., 2022).

Indirect Signs

Indirect signs include dilation of the bile ducts above the level of obstruction. In the presented clinical observation, a patient post-cholecystectomy with pain in the right upper quadrant showed moderate diffuse dilation of the right and left intrahepatic ducts against the background of echogenic structures in the distal parts of the right and left hepatic ducts (Textbook of Diagnostic Sonography, 9th ed., 2023).

The Role of Contrast-Enhanced Ultrasound

The role of contrast-enhanced ultrasound (CEUS) in assessing the biliary system in bile duct diseases has been described (ExpertDDx: Abdomen and Pelvis, 3rd ed., 2023). Specific criteria related to choledocholithiasis — [specify].

Differential Guidelines for Stones (General Principles)

By analogy with stones in other locations, the key differential signs of a stone are hyperechogenicity, acoustic shadow, and mobility when changing body position. In small stones (< 3–4 mm), the acoustic shadow may be unclear or absent; to improve visualization, it is recommended to reduce gain and use a high-frequency probe (Verified Answers from the Medtrain Consortium, 2026). The applicability of these technical techniques to bile ducts — [specify].