Liver and gallbladder anatomy

Liver: position and surfaces

• Mostly in the right hypochondrium and epigastrium under the diaphragm; moves with breathing.
• Percutaneous liver biopsy is done in the right 8th–9th intercostal space in the midaxillary line, in full expiration (lung and pleura out of the way), passing through the costodiaphragmatic recess of the pleura.
• Bare area: posterior surface between the layers of the coronary ligament, in direct contact with the diaphragm.
• Ligaments: falciform ligament with the ligamentum teres (obliterated left umbilical vein) in its free edge; ligamentum venosum (ductus venosus); coronary and triangular ligaments; lesser omentum (hepatogastric and hepatoduodenal parts).
• Hepatorenal pouch (Morison pouch): lowest part of the peritoneal cavity in a supine patient, where fluid collects.

Lobes and segments

• Anatomical lobes: right and left at the falciform ligament; caudate (between IVC and ligamentum venosum) and quadrate (between gallbladder and ligamentum teres) on the inferior surface.
• Functional division: the Cantlie line, from the gallbladder fossa to the IVC, splits the liver into right and left halves, each with its own hepatic artery, portal vein and bile duct branches.
• Couinaud segments I–VIII: each has its own portal pedicle and drains to hepatic veins running between segments, so segments can be resected separately. Segment I (caudate) drains straight into the IVC by its own veins and is supplied from both sides, so it is spared and enlarges in Budd–Chiari syndrome.

Blood supply and portal triad

• Portal vein (about 75% of flow, half the oxygen): formed behind the neck of the pancreas by the superior mesenteric and splenic veins.
• Hepatic artery proper (about 25% of flow, half the oxygen) from the common hepatic artery (coeliac trunk).
• Hepatic veins (right, middle, left) drain into the IVC.
• In the free edge of the lesser omentum: common bile duct (right, anterior), hepatic artery (left, anterior), portal vein (posterior). The epiploic foramen lies behind; squeezing the free edge (Pringle manoeuvre) controls hepatic bleeding.
• Portosystemic anastomosis at the umbilicus: paraumbilical veins (along the ligamentum teres, portal) join the epigastric veins of the abdominal wall (systemic). In portal hypertension they dilate, radiating from the umbilicus (caput medusae), with blood flowing away from it. In IVC obstruction, dilated veins flow upwards from below the umbilicus.
• Liver zones: blood enters at portal tracts (zone 1) and leaves at the central vein (zone 3). Zone 3 has the least oxygen and the most smooth ER and cytochrome P450, so it is hit by ischaemia and paracetamol. Eclampsia classically causes periportal (zone 1) haemorrhagic necrosis, an exception worth remembering.
• Regeneration: after partial hepatectomy, Kupffer cell cytokines (TNF, IL-6) prime hepatocytes, then hepatocyte growth factor from stellate and endothelial cells is the main mitogen; volume returns within weeks.

Biliary tree

The right and left hepatic ducts form the common hepatic duct, which is joined by the cystic duct to form the common bile duct (about 7–8 cm). The CBD runs in the free edge of the lesser omentum, behind the first part of the duodenum, then in a groove on or through the back of the head of the pancreas, and joins the main pancreatic duct at the ampulla of Vater, opening on the major duodenal papilla in the second part of the duodenum through the sphincter of Oddi.

• Blood supply of the supraduodenal CBD is from small axial arteries running at 3 and 9 o'clock, mainly from below (gastroduodenal and retroduodenal arteries). Stripping the duct or a duct-to-duct repair can leave it ischaemic and cause a stricture; major injuries are repaired by Roux-en-Y hepaticojejunostomy.
• Courvoisier law: in painless obstructive jaundice, a palpable gallbladder is unlikely to be from stones, because stones cause chronic inflammation that leaves a small fibrotic gallbladder. It suggests carcinoma of the pancreatic head or lower bile duct.
• Ascending cholangitis: stone in the CBD with infection: Charcot triad of fever with rigors, jaundice and right upper quadrant pain. Treat with antibiotics and early ERCP to drain the duct.

Gallbladder

• Parts: fundus (at the tip of the right 9th costal cartilage, where the lateral rectus border meets the costal margin), body, neck with Hartmann pouch (where stones lodge) and cystic duct (spiral valves of Heister).
• Cystic artery usually arises from the right hepatic artery in Calot triangle; variations are common.
• Ducts of Luschka (subvesical ducts): small ducts in the gallbladder bed draining directly to the right hepatic duct system; after cholecystectomy they can leak bile even when cystic duct clips and the CBD are intact. The commonest leak site is still the cystic duct stump.
• Concentration of bile: the mucosa actively absorbs Na⁺ (with Cl⁻ and HCO₃⁻) and water follows, concentrating bile salts 5–10 times; bile stays isosmotic because bile salts form micelles. CCK contracts the gallbladder and relaxes the sphincter of Oddi.
• Cholesterol stones form when bile is supersaturated with cholesterol relative to bile salts and lecithin; rapid weight loss (bariatric surgery), oestrogen, pregnancy and obesity all do this. Gallbladder stasis and nucleation add to it.
• Pain: visceral (T6–T9) to the epigastrium; parietal inflammation to the right upper quadrant; diaphragmatic irritation to the right shoulder (phrenic, C3–C5); also to the inferior angle of the right scapula.

Stone complications with an anatomical basis

Calot triangle (cystohepatic triangle)

• Boundaries: cystic duct laterally, common hepatic duct medially, inferior surface of the liver above. (Calot's original upper border was the cystic artery.)
• Contents: cystic artery, often the right hepatic artery, the cystic lymph node (of Lund), connective tissue.
• Critical view of safety before clipping: the triangle cleared of fat, only two structures entering the gallbladder, and the lower third of the gallbladder separated from the liver bed.
• Rouvière sulcus: a cleft on the inferior surface of the right lobe marking the level of the bile duct; all dissection is kept above (ventral to) it.

Liver tumours in brief

Metastases are the commonest liver malignancy. Hepatocellular carcinoma arises in cirrhosis (hepatitis B and C, alcohol, aflatoxin) and raises AFP. Hepatic adenoma is linked to the oral contraceptive pill and anabolic steroids.

Remember Cantlie line from gallbladder fossa to IVC divides the liver; Calot triangle holds the cystic artery.

Exam trap The cystic artery usually arises from the right hepatic artery, which may itself loop through Calot triangle.

Exam trap Eclampsia damages zone 1; ischaemia and paracetamol damage zone 3.

How FCPS asks about this

• Site for percutaneous liver biopsy: right 8th–9th space, midaxillary line, in expiration.
• Stone in Hartmann pouch compressing the common hepatic duct: Mirizzi syndrome.
• Fever with rigors, jaundice and RUQ pain: cholangitis; antibiotics and ERCP.
• Caput medusae: paraumbilical veins anastomosing with epigastric veins.
• Why the supraduodenal bile duct strictures after repair: axial arteries at 3 and 9 o'clock.
• Landmark keeping dissection safe at cholecystectomy: Rouvière sulcus; bile leak from the bed is a duct of Luschka.
• Air in the biliary tree with small bowel obstruction: gallstone ileus through a cholecystoduodenal fistula.