Unit 17 Question Bank

A recurring TMU past-paper question.

The celiac trunk

Arises from the front of the abdominal aorta at about T12 and supplies the foregut, down to the descending part of the duodenum. It has three branches.

1. Left gastric artery — ascends to the cardia, gives oesophageal branches, then runs along the lesser curvature
2. Common hepatic artery, dividing into:
   • Proper hepatic artery → right hepatic (→ cystic artery), left hepatic, and the right gastric artery
   • Gastroduodenal artery → right gastro-omental and superior pancreaticoduodenal arteries
3. Splenic artery — along the upper border of the pancreas, giving pancreatic branches, then the short gastric and left gastro-omental arteries

The five arteries of the stomach

The two arteries on each curvature anastomose end to end, giving the stomach a rich collateral supply — which is why gastric infarction is rare and why several vessels can be ligated at partial gastrectomy.

Real question — TMU 2021–22 final, definition 4.

Definition

A small triangular region on the inferior surface of the liver, exposed during cholecystectomy. Also called Calot's or the cystohepatic triangle.

Boundaries

• Right (laterally): the cystic duct
• Left (medially): the common hepatic duct
• Above: the inferior surface of the liver

Contents

• The cystic artery, usually a branch of the right hepatic artery
• The right hepatic artery itself
• A cystic lymph node (of Lund)

Surgical importance

• The surgeon must identify and clip the cystic artery and cystic duct within this triangle
• Mistaking the common bile duct for the cystic duct and dividing it is the commonest cause of bile duct injury in laparoscopic cholecystectomy, and may require major reconstructive surgery
• The critical view of safety — clearing the triangle of all fat and fibrous tissue until only two structures are seen entering the gallbladder — exists specifically to prevent this
• The cystic artery's origin is variable, so it must be seen rather than assumed

Dual supply of the liver

• Hepatic portal vein — carries about 75% of the blood, deoxygenated but nutrient-rich, from the gut
• Proper hepatic artery — carries about 25%, oxygenated, from the celiac trunk via the common hepatic artery

Both enter at the porta hepatis and divide into right and left branches. They reach the liver in the free edge of the lesser omentum — the hepatoduodenal ligament — with the artery on the left, the bile duct on the right and the portal vein behind.

Gallbladder

• Supplied by the cystic artery, usually from the right hepatic artery, running in Calot's triangle
• Venous drainage is by small veins passing directly into the liver substance, and by a cystic vein to the portal vein

Venous drainage of the liver

Three hepatic veins leave the posterior surface and drain directly into the inferior vena cava.

Clinical

Because inflow is dual, occlusion of the hepatic artery alone is often survivable, whereas the Pringle manoeuvre — compressing the free edge of the lesser omentum — occludes both at once and stops nearly all hepatic inflow.

The relevant anatomy

The first part (superior part) of the duodenum is the commonest site of duodenal ulceration. Its two walls have completely different relations:

• Posteriorly lies the gastroduodenal artery, a branch of the common hepatic artery, running directly behind the duodenum — together with the bile duct and portal vein
• Anteriorly lies the peritoneal cavity, since the first part of the duodenum is intraperitoneal

Consequences

• A posterior ulcer erodes through the wall into the gastroduodenal artery → massive upper gastrointestinal haemorrhage, presenting with haematemesis and melaena, and one of the classic causes of exsanguinating GI bleeding
• An anterior ulcer erodes into the peritoneal cavity → perforation, with sudden severe pain, board-like rigidity and free gas under the diaphragm on an erect chest X-ray

The general principle

Same organ, same disease, opposite complication — decided entirely by which surface the lesion sits on and what lies behind it. It is a good illustration of why regional anatomy, rather than systemic anatomy, is what predicts clinical behaviour.

Definition

The part of the peritoneal cavity lying above the transverse colon and its mesocolon.

Contents

• Liver and gallbladder
• Stomach
• Spleen
• Superior part of the duodenum
• Also the omental bursa (lesser sac) behind the stomach, and the hepatorenal recess between liver and right kidney

Arterial supply — one trunk

All of it is foregut, and the foregut has a single artery: the celiac trunk, arising at T12 and supplying down to the descending part of the duodenum, where the midgut and the superior mesenteric artery take over.

• Left gastric — stomach and lower oesophagus
• Common hepatic → proper hepatic (liver, gallbladder via the cystic artery, and right gastric) and gastroduodenal (right gastro-omental, superior pancreaticoduodenal)
• Splenic — spleen, pancreas, short gastric and left gastro-omental arteries

Why the division matters clinically

Infection or blood in the supracolic compartment collects in the hepatorenal recess and subphrenic spaces, and communicates with the infracolic compartment through the paracolic gutters — which is how a perforated appendix can produce a subphrenic abscess.