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Common hepatic duct

The common hepatic duct is a major component of the extrahepatic biliary system, formed by the junction of the right and left hepatic ducts emerging from the liver hilum. It runs a short course before joining the cystic duct to form the common bile duct (CBD). It serves as a conduit for bile drainage from the liver to the duodenum (via the CBD).

This duct is a critical structure in hepatobiliary anatomy and is frequently evaluated in radiology for gallstone disease, biliary obstruction, cholangitis, and malignancies.

Synonyms

  • Extrahepatic hepatic duct

  • Proximal common bile duct (before cystic duct)

  • Hepatic duct trunk

Origin, Course, and Termination

  • Origin: Formed by union of right and left hepatic ducts at the porta hepatis

  • Course: Descends for ~2–4 cm within the hepatoduodenal ligament, anterior to the portal vein and medial to the hepatic artery proper

  • Termination: Joins the cystic duct to form the common bile duct

Relations

  • Anteriorly: Hepatic artery proper and peritoneum of hepatoduodenal ligament

  • Posteriorly: Portal vein

  • Laterally: Right: cystic duct; Left: hepatic artery branches

  • Inferiorly: Continuous with common bile duct

Function

  • Conveys bile from intrahepatic ducts (liver) into the common bile duct

  • Essential for digestion and absorption of fats (via bile delivery to duodenum)

  • Provides a key landmark in hepatobiliary surgery and liver transplantation

Clinical Significance

  • Gallstones (choledocholithiasis): May obstruct the duct → jaundice, cholangitis

  • Strictures: Can be benign (post-surgical) or malignant (cholangiocarcinoma)

  • Biliary atresia: In pediatrics, duct absence or fibrosis may occur

  • Iatrogenic injury: Common complication of cholecystectomy

  • Imaging role: Evaluated by ultrasound, CT, MRCP, and intraoperative cholangiography

MRI Appearance

T1-weighted images:

  • Duct lumen: dark (low signal) due to bile fluid

  • Wall: thin, barely perceptible, may enhance with contrast

T2-weighted images:

  • Lumen: bright (high signal) due to fluid

  • Wall: hypointense thin rim

STIR (Short Tau Inversion Recovery):

  • Bile: bright hyperintense signal

  • Fat suppressed, improving duct-to-fat contrast

T1 Fat-Sat Post-Contrast:

  • Duct wall may enhance minimally

  • Obstructed or inflamed ducts: irregular wall enhancement, mural thickening

T2 Fat-Saturated HASTE (single-shot):

  • Common hepatic duct: very bright signal (fluid-filled lumen)

  • Provides rapid screening for obstruction, strictures, or stones

  • Stones appear as dark signal voids within bright duct fluid

T2 TSE Fat-Saturated 3D (MRCP sequence):

  • Duct visualized as a high-signal tubular structure

  • Allows 3D reconstruction of the entire biliary tree

  • Excellent for detecting strictures, dilatation, or intraluminal defects

Thick-slab T2 Fat-Saturated HASTE:

  • Depicts the duct as a bright tubular structure on a projectional MRCP image

  • Useful for quick overview of biliary anatomy in a single thick slice

  • Stones or air bubbles: appear as dark filling defects against bright fluid

CT Appearance

Non-Contrast CT:

  • Duct usually not well seen unless dilated

  • Appears as a low-attenuation tubular structure in hepatoduodenal ligament

  • Stones: hyperdense if calcified, otherwise often missed

Post-Contrast CT:

  • Duct wall enhances subtly

  • Dilatation visible as low-density tubular structure anterior to portal vein

  • Pathology (strictures, tumors): appear as wall thickening, enhancing masses, or abrupt narrowing

MRI image

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MRI image

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MRI image

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