Anatomy Thorax Abdomen · Year 1 · from Anatomy Thorax Abdomen
Case 3: Gastric Outlet Obstruction
Clinical Presentation
A 48-year-old male with a long history of peptic ulcer disease presents with progressive nausea, vomiting, and early satiety over 2 weeks. He reports that his vomitus contains partially digested food eaten many hours earlier but no bile. He has lost 5 kg over the past month. On examination, he appears dehydrated with dry mucous membranes. A succession splash is elicited on abdominal examination.
Laboratory studies reveal hypokalemic, hypochloremic metabolic alkalosis (pH 7.52, K+ 2.8 mEq/L, Cl- 88 mEq/L) from loss of gastric acid and potassium. Nasogastric tube insertion produces 1.5 liters of retained gastric contents. Upper endoscopy reveals severe scarring and stenosis of the pyloric channel from chronic peptic ulcer disease, preventing passage of the endoscope. After correction of electrolyte abnormalities and nutritional optimization, he undergoes laparoscopic pyloroplasty with relief of obstruction.
Key Anatomical Points
- The pylorus is the sphincter at the gastroduodenal junction, formed by a thick ring of circular smooth muscle
- The pylorus lies at the level of the L1 vertebra at the transpyloric plane
- Chronic inflammation and scarring can lead to pyloric stenosis and gastric outlet obstruction
- The pylorus is innervated by vagal fibers that promote relaxation and sympathetic fibers that cause contraction
Key Learning Points
- Vomiting of non-bilious material indicates obstruction proximal to the ampulla of Vater (D2)
- Succession splash is heard when the stomach is distended with retained fluid and air
- Loss of gastric acid (HCl) causes hypochloremic metabolic alkalosis with paradoxical aciduria
- The left gastric vein drains to the portal system and communicates with esophageal veins at the cardia