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Cholelithiasis

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 Extrahepatic Biliary Anatomy

General

Extrahepatic Biliary Anatomy

Gallbladder

The gallbladder is a hollow, pear-shaped organ which lies in the gallbladder fossa along the visceral surface of the liver.  It has a capacity of up to 50ml and is typically 7-10 cm in length.  By convention, it is divided into three parts.  The fundus is the blind, wide end of the gallbladder, the body makes up the majority of the organ, and the neck is the narrow, tapered end which is contiguous with the cystic duct and drains through the spiral valve.

Cystic Duct

The cystic duct is the outflow tract of the gallbladder.  It connects the neck of the gallbladder to the common hepatic duct, which becomes the common bile duct.  The cystic duct is typically about 4cm in length, and courses between the layers of the lesser omentum, usually parallel to the common hepatic duct, before joining to form the common bile duct and eventually meeting the pancreatic duct to drain into the duodenum at the Ampulla of Vater.

Blood Supply and Nerves

The gallbladder and cystic duct are supplied principally by the cystic artery, which typically branches from the right hepatic artery (75% of the time).  Variations in the origin and course of the cystic artery do occur in approximately 25% of individuals, which can be of clinical significance during gallbladder removal.

The veins of the gallbladder neck (cystic veins) communicate with veins along the cystic and bile ducts.  They may drain through the portal vein to the liver, or after joining the veins of the hepatic ducts and upper bile duct.  In addition, small cystic veins from the fundus and body of the gallbladder may pass directly into the liver.

Lymphatic drainage of the gallbladder courses to the hepatic nodes through the cystic lymph nodes, which are typically located near the neck of the gallbladder.

The gallbladder and cystic duct are supplied by 3 types of innervation, which course with the cystic artery.  The celiac plexus supplies sympathetic innervation, the vagus nerve supplies parasympathetic innervation, and the right phrenic nerve conveys sensory information.

 

Arteries Cystic artery (from right hepatic artery, 75% of the time)
Veins Cystic vein
Lymphatics Cystic lymph nodes to hepatic lymph nodes
Nerves Celiac plexus (symp), vagus nerve (para), and right phrenic nerve (sensory)

Dissection Considerations

As mentioned above, there are variations of the origin and course of the cystic artery that must be borne in mind whenever gallbladder dissection is attempted.  In approximately 75% of individuals, the cystic artery takes off from the right hepatic artery.  Other variations include originating from the left hepatic artery (6%), the proper hepatic artery (2-3%), and from the gastroduodenal artery (1%).  Additionally, the gallbladder may be supplied by one (79% of cases), two (19.9%), or three cystic arteries (1.8%).

Variations in the course of the cystic duct have also been noted.  The cystic duct may meet the common hepatic duct high on the common bile duct (high union), low on the common bile duct (low union), or may take a tortuous course before meeting the hepatic ducts (swerving course).  Understanding these variations in bile duct anatomy is important for surgeons when they ligate this structure during cholecystectomy.