Abdomen:Hollow viscus:Gallbladder

The **gallbladder** is a pear-shaped musculomembranous sac, lodged in a fossa under the liver which stores and concentrates the bile secreted by the liver. It typically measures from 7 to 10 cm in length and 2.5 cm in breadth at its widest part. It holds from 30 to 35 mL of bile when distended, although if obstructed it can distend to accommodate up to 300 mL.

It is divided into a fundus, body, and neck.

* Fundus: Wide tip of GB, projects below liver edge (usually) at the transpyloric.
* Body: Contacts liver, duodenum & transverse colon
* Neck: Narrowed, tapered and tortuous; joins cystic duct
* Cystic duct: 3-4 cm long, connects GB to common hepatic duct;

The upper surface of the gallbladder is attached to the liver by connective tissue, vessels and bile ducts. The under surface is covered by peritoneum, which is reflected on to it from the surface of the liver.

Relations

* superiorly: liver
* inferiorly: transverse colon, D1 segment of the duodenum (or pylorus of the stomach)
* anteriorly: transverse colon, 9th costal cartilage

Cystic duct

 The **cystic duct** connects the neck of the gallbladder to the common hepatic duct (CHD) which forms the CBD at the junction. The cystic duct is approximately 2-3cm long and 2-3mm in diameter.

* marked by spiral folds (of Heister); helps to regulate bile flow to & from GB

* The cystic artery (branch of right hepatic artery) can often travel behind the cystic duct to supply the gallbladder within the Carlot triangle.

* Variant anatomy
	+ low cystic duct insertion - into the distal-third of the CHD (~10%)
	+ medial cystic duct insertion - into the left, not the right, side of the CHD (~15%)
	+ parallel cystic duct course - courses parallel to the CHD for at least 2cm (~10%)

Blood supply

* **Arterial:** cystic artery, a branch of the right hepatic that cross the Calot triangle. However variation arising from the common hepatic artery, gastroduodenal artery is possible.

* **Venous:** There is no single cystic vein, but rather small veins pass from directly to the liver through the gallbladder fossa and into the right branch of the portal vein.

Nerve supply

The gallbladder receives both sympathetic and vagal supply:

* sympathetic: via the coeliac plexus
* vagual: via the hepatic branches of anterior vagal trunk

Lymphatic supply

* Lymphatics of the gallbladder drain toward the porta hepatis and to portal nodes.

Variant anatomy

The gallbladder has a number of variations in its anatomy based on:

* morphology:
	+ Phrygian cap: the fundus is sometimes folded back upon itself
	+ Hartmann pouch (infundibulum):
		- in some instances the neck is focally dilated (adjacent to the body)
		- probably pathological, related to cholelithiasis
	+ occasionally the whole gallbladder is invested by the serous membrane, and is then connected to the liver by a kind of mesentery, rendering the organ prone to torsion
* number:
	+ accessory gallbladder
		- gallbladder duplication
		- gallbladder triplication
	+ gallbladder agenesis
* location:
	+ left-sided gallbladder: extremely rare (< 0.20%) 5
		- located to the left of the falciform ligament without situs inversus
		- normally not diagnosed on pre-operative imaging (i.e. apparent only at operation)