Gallbladder and cystic duct

The cystic duct  is a tubular structure that connects the neck of the gallbladder to the extrahepatic ductal system. It is 2-4 cm. in length and its lumen is about 2.6 +/- 0.7 mmm. The shape of the cystic duct varies, as it can be straight, angled, or acutely curved.

The mucosa of the cystic duct presents with 2-10 crescent-shaped folds that create a spiral-shaped inner structure referred to as the "Valve of Heister", first described by Lorenz Heister in 1732. These folds become smaller and scarcer towards the distal portion of the duct.

The cystic duct can present with several anatomical variations, from total absence where the neck of the gallbladder empties directly in to the common bile duct, to duplication, and even rare occasions where the cystic duct empties separately into the duodenal lumen.

The cystic duct is an important surgical landmark as it is one of the boundaries of the cystohepatic triangle or  "Triangle of Calot", described by Jean-Francois Calot (1861 - 1944), which determines the location of the cystic artery, a critical structure that needs to be ligated and transected during a cholecystectomy.

Sources:
1 "Cystic Duct and Heister’s “Valves” Dasgupta,C, Stringer, MD, Clin Anat (2005) 18:81–87
2. "Tratado de Anatomia Humana" Testut et Latarjet 8 Ed. 1931 Salvat Editores, Spain
3. "Anatomy of the Human Body" Henry Gray 1918. Philadelphia: Lea & Febiger
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