The image shows a transverse view of the left lobe of the liver with the portal triads clearly visible. The "parallel channel" or "double barrel" sign is observed—where dilated intrahepatic bile ducts run alongside the portal veins, creating a characteristic sonographic pattern of paired anechoic (black) tubular structures.
This sonographic feature is diagnostic for dilated intrahepatic bile ducts and is typically seen in obstructive jaundice or biliary obstruction from conditions such as:
Choledocholithiasis (stone in the common bile duct)
Stricture or mass compressing the bile ducts
Cholangiocarcinoma
The intrahepatic bile ducts normally are too small to visualize clearly unless dilated. Their dilation gives the liver a "too many tubes" appearance, where bile ducts become as prominent as the portal veins.
Comparison of answer choices:
A. Normal intrahepatic ducts are not usually seen this clearly or prominently on ultrasound.
B. Dilated intrahepatic — Correct. The parallel channel sign supports this diagnosis.
C. Dilated common bile duct would be visualized extrahepatically, typically anterior to the portal vein near the head of the pancreas.
D. Dilated common hepatic duct is also extrahepatic and seen in the porta hepatis, not within the liver parenchyma.
[References:, Rumack CM, Wilson SR, Charboneau JW, Levine D. Diagnostic Ultrasound, 5th ed. Elsevier; 2017., Hagen-Ansert SL. Textbook of Diagnostic Sonography, 8th ed. Elsevier; 2017., Taylor KJW, Burns PN, Wells PNT. Clinical Applications of Doppler Ultrasound. Raven Press; 1990., , ]
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