Common hepatic duct
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At the time the article was created Chia Wei Oh had no recorded disclosures.View Chia Wei Oh's current disclosures
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The common hepatic duct (CHD) is formed by the right and left hepatic ducts junction. It joins the cystic duct to form the common bile duct (CBD). It is approximately 4 cm long and 4 mm in diameter, typically.
It is not always possible to confidently see where the cystic duct enters the common hepatic duct to form the common bile duct on ultrasound imaging. Therefore, some commonly use the term common duct (CD) as a term conflating the common hepatic and common bile ducts. This is contrary to Gray's Anatomy, which uses the term common duct to refer to the duct formed by the confluence of the CBD and the pancreatic duct.
Of note, for decades, what had been labeled CBD in much radiology literature is now known actually, usually to have been the CHD. Thus, the oft-quoted normal value of < 6 mm (measured inner aspect of wall to inner aspect of the wall, typically by ultrasound) in adults actually refers to the CHD in most cases. The CHD is best measured when the patient is fasting, at the porta hepatis, typically parallel and anterior to the portal vein. In recent years, 7 mm has been proposed as a better cut-off.
Also, for decades, it had been thought that the CHD (then termed the CBD, more often than not erroneously) could increase as much as 4 mm after cholecystectomy and by age as much as 1 mm per decade after age 60. This has not been supported by subsequent studies, which indicate that the CHD diameter may increase only by 0.1--0.2 mm per decade and increases only about 1 mm after cholecystectomy.
The diameter of the actual CBD is far more variable, not readily affording a valid cut-off value. It is seen more inferiorly by ultrasound, usually having exited the porta toward the pancreas.