By CRUX OF SURGERY in MRCS Part A — 26 Feb 2026

Peptic Ulcer Disease

A patient on NSAIDs develops haematemesis. What is the mechanism by which aspirin contributes to the formation of gastric ulcers?

((Inhibit prostaglandin synthesis::☑️ Aspirin inhibits COX-1, reducing PGE₂, which decreases mucus, bicarbonate secretion and mucosal blood flow))
((Inhibit somatostatin::Would increase acid secretion rather than impair mucosal protection))
((Inhibit gastrin::Would reduce acid production))
((Inhibit secretin::Would reduce bicarbonate secretion from pancreas but is not the primary gastric mechanism))
((Inhibit cholecystokinin::Not involved in gastric mucosal protection))

💡 In the stomach, prostaglandins, especially PGE₂, protect gastric mucosa by stimulating mucus and bicarbonate secretion, maintaining mucosal blood flow, and limiting acid production. Aspirin, a COX-1 inhibitor, inhibits prostaglandin production, compromising this defense.

Prostaglandins (PGE₂, PGI₂) → EP₃ receptors on gastric parietal cells → ↓cAMP → ↓ HCl secretion
Prostaglandins (PGE₂, PGI₂) → EP₄/EP₂ receptors on surface mucous cells → ↑cAMP → ↑mucus/bicarbonate secretion

A patient is bleeding from an anterior gastric ulcer between the antrum and body of the stomach. Where’s the source of the bleeding?

((Short gastric arteries::Supply the fundus via branches of the splenic artery))
((Left gastroepiploic artery::Runs along the greater curvature of the stomach))
((Right gastroepiploic artery::Supplies the greater curvature near the pylorus))
((Left gastric artery::☑️ Runs along the lesser curvature and supplies the body/antral region))

💡 An anterior gastric ulcer located between the antrum and the body of the stomach lies along the lesser curvature. The primary arterial supply to this region is the left gastric artery.

A patient has a posterior perforating duodenal ulcer bleeder. What is the artery most likely to be injured?

((Right hepatic artery::Runs in the hepatoduodenal ligament and is not directly posterior to the first part of the duodenum))
((Left gastric artery::Supplies the lesser curvature of the stomach))
((Right gastroepiploic artery::Runs along the greater curvature of the stomach))
((Gastroduodenal artery::☑️ Lies posterior to the first part of the duodenum and is classically eroded by posterior duodenal ulcers))

Endoscopy shows bleeding from the first part of the duodenum. There is also a deep ulcer posteriorly. Which blood vessel is responsible for the bleeding?

((Right hepatic artery::Runs in the hepatoduodenal ligament and is not directly posterior to the first part of the duodenum))
((Left gastric artery::Supplies the lesser curvature of the stomach, not the posterior duodenum))
((Right gastroepiploic artery::Runs along the greater curvature of the stomach))
((Gastroduodenal artery::☑️ Lies posterior to the first part of the duodenum and is classically eroded by posterior duodenal ulcers))

💡 The first part of the duodenum lies anterior to the gastroduodenal artery. A perforating posterior duodenal ulcer, especially in the first part of the duodenum, is most likely to erode into and injure the gastroduodenal artery.

A 45-year-old male complains of a long history of upper abdominal pain due to chronic use of analgesics. He now presents with severe agonising abdominal pain. You suspect a perforated duodenal ulcer. What is the best investigation modality to detect free air in this abdomen?

((CT scan::☑️ CT has a diagnostic accuracy of ~98% for pneumoperitoneum, detects small volumes of free air, identifies the site of perforation, and can exclude alternative diagnoses such as acute pancreatitis))
((Erect chest X-ray::Can demonstrate free air under the diaphragm but is less sensitive than CT))
((Barium study::Contraindicated in suspected perforation due to risk of barium peritonitis))
((Ultrasound scan::Poor sensitivity for detecting free intraperitoneal air))

A 35-year-old pregnant lady presented to A&E with acute abdominal pain and is suspected to have a perforated duodenal ulcer. What is the best investigation to organise?

((CT scan::☑️ Most accurate investigation for detecting perforation and free air; justified in pregnancy when maternal benefit outweighs radiation risk))
((Ultrasound scan::Safe in pregnancy but not sensitive for detecting pneumoperitoneum))
((MRI scan::Avoids radiation but not reliable for detecting free intraperitoneal air))
((Erect chest X-ray::Lower radiation dose and may demonstrate free air, but less sensitive than CT))

A 45-year-old man with a long history of upper abdominal pain due to chronic analgesic use presents with severe, agonising abdominal pain. You suspect a perforated duodenal ulcer. What is the best investigation to detect free air in the abdomen?

((CT abdomen pelvis with contrast::☑️ Most sensitive investigation for detecting pneumoperitoneum and identifying the site of perforation))
((CT abdomen pelvis without contrast::Can detect free air but contrast-enhanced CT better defines perforation and associated pathology))
((Barium swallow::Contraindicated in suspected perforation due to risk of barium peritonitis))
((Erect chest X-ray::Useful initial test to demonstrate free air under the diaphragm but less sensitive than CT))