Gallbladder

Vesica biliaris (vesica fellea)

Also known as: gall bladder, cholecyst

The gallbladder is a pear-shaped sac about 7–10 cm long that sits in a fossa on the underside of the liver. It stores and concentrates bile between meals and contracts in response to CCK to deliver it to the duodenum.

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Overview

Length≈7–10 cm

Capacity≈30–50 mL

Bile concentration≈5–10× (up to ≈20×)

Surface marking (fundus)Tip of right 9th costal cartilage, MCL

The gallbladder lies in the gallbladder fossa on the visceral surface of the liver, at the junction of the right lobe and the quadrate lobe on the Cantlie line. It holds about 30–50 mL. It has three parts. The fundus projects beyond the inferior border of the liver and touches the anterior abdominal wall at the tip of the right 9th costal cartilage in the midclavicular line, where the linea semilunaris crosses the costal margin. The body lies against the transverse colon and the 2nd part of the duodenum. The neck narrows and turns into the cystic duct. A pouch at the neck, Hartmann pouch, is not a normal feature, but stones often lodge there.

The mucosa is thrown into a honeycomb of folds lined by tall simple columnar epithelium with microvilli. The wall has no muscularis mucosae and no submucosa. Its smooth muscle is irregularly arranged, and outside it are perimuscular connective tissue and, on the free surface, serosa.

The epithelium actively absorbs Na⁺, with Cl⁻ and water following. This concentrates bile about 5–10-fold (up to about 20-fold) and acidifies it slightly. Between meals the sphincter of Oddi is closed, so bile backs up into the gallbladder. When fat and amino acids reach the duodenum, CCK contracts the gallbladder and relaxes the sphincter of Oddi, and bile is expelled.

Location: Right upper quadrant, in the gallbladder fossa on the inferior surface of the liver. The fundus is at the tip of the right 9th costal cartilage in the midclavicular line.

Parts & subdivisions

Fundus
Rounded blind end projecting below the liver edge; contacts the anterior abdominal wall.
Body
Main part, in contact with the liver above and the transverse colon and duodenum below.
Neck
Tapered part that continues as the cystic duct. A Hartmann pouch here is a common site of impacted stones.
Cystohepatic triangle (of Calot)
Bounded by the cystic duct, the common hepatic duct and the inferior surface of the liver. Contains the cystic artery (usually from the right hepatic artery) and the cystic lymph node. It must be dissected to achieve the "critical view of safety" before clipping during cholecystectomy.

Anatomy

Innervation: Coeliac plexus: sympathetic fibres (visceral pain afferents, roughly T6–T9) and vagal parasympathetic fibres (contraction). Pain is referred to the epigastrium and right hypochondrium and can radiate to the right scapula. The right phrenic nerve supplies the overlying peritoneum and diaphragm, giving shoulder-tip pain.
Arterial supply: Cystic artery, usually from the right hepatic artery and running through Calot's triangle. Variations are common.
Venous drainage: Small cystic veins drain directly into the liver or the portal vein; there is no single "cystic vein" to the portal trunk.
Lymphatic drainage: Cystic node (of Lund) at the neck → hepatic nodes → coeliac nodes.
Relations: Superior: liver. Inferior and posterior: transverse colon and the 1st and 2nd parts of the duodenum. Anterior (fundus): anterior abdominal wall.
Histology: Mucosa with tall columnar absorptive epithelium and lamina propria, without muscularis mucosae or submucosa. Rokitansky–Aschoff sinuses (mucosal herniations into the muscle) are seen in chronic cholecystitis.

Function

Stores bile between meals.
Concentrates bile about 5–10-fold by active Na⁺ absorption.
Delivers a bolus of bile to the duodenum after a meal (CCK).
Adds mucus to bile.

Regulation: CCK (main) and vagal ACh (cephalic phase) cause contraction. Between meals, motilin-associated partial emptying occurs with the migrating motor complex. Somatostatin inhibits it.

Clinical significance

Biliary colic and acute cholecystitis

A stone temporarily blocking the cystic duct causes biliary colic, a constant right upper quadrant or epigastric pain after a fatty meal that settles within hours. Persistent obstruction causes acute cholecystitis, with fever, leucocytosis and a positive Murphy sign (inspiration halts on palpation under the right costal margin). Ultrasound shows a thickened wall, pericholecystic fluid and a sonographic Murphy sign.

Courvoisier law

A palpable, non-tender gallbladder in a jaundiced patient is unlikely to be due to stones, because a gallbladder repeatedly inflamed by stones becomes fibrotic and shrunken. It suggests distal malignant obstruction, such as carcinoma of the pancreatic head.

Gallbladder carcinoma and porcelain gallbladder

Associated with long-standing gallstones and calcification of the wall (porcelain gallbladder). It is often detected late, with a poor prognosis.

Mnemonics

Gallstone risk: the 5 Fs

Female, Fat, Fertile, Forty, Fair.

Test yourself

Gallbladder contraction and relaxation of the sphincter of Oddi after a fatty meal are mainly caused by:

Secretin
Gastrin
Cholecystokinin
Somatostatin

Answer: Cholecystokinin

Fatty acids and amino acids in the duodenum release CCK from I cells. CCK contracts the gallbladder, relaxes the sphincter of Oddi and stimulates pancreatic enzyme secretion. Somatostatin inhibits gallbladder emptying.