A 52-year-old man from Delhi presents with severe epigastric pain radiating to the back, accompanied by steatorrhoea and weight loss over 3 months. On examination, he is jaundiced. Serum amylase is 1200 U/L (normal <100), lipase 2400 U/L. Abdominal ultrasound shows a dilated common bile duct (8 mm) and a hypoechoic mass in the pancreatic head. Fasting serum glucose is 180 mg/dL. Which of the following best explains the steatorrhoea in this patient?

Explanation

## Pathophysiology of Steatorrhoea in Pancreatic Insufficiency **Key Point:** Steatorrhoea in pancreatic cancer results from impaired pancreatic enzyme secretion, not bile acid metabolism or intestinal absorption defects. ### Mechanism of Fat Malabsorption In pancreatic head obstruction: 1. Pancreatic acinar cells cannot secrete lipase and colipase into the duodenum 2. Lipase is the primary enzyme responsible for triglyceride hydrolysis (cleaves 70% of dietary fat) 3. Without adequate lipase and colipase, dietary triglycerides remain undigested 4. Undigested fat is excreted in stool → steatorrhoea **High-Yield:** Pancreatic lipase requires colipase (a cofactor secreted by the pancreas) to function optimally in the presence of bile salts. Both are reduced in pancreatic insufficiency. ### Why Bile Acid Metabolism Is Intact The patient has: - Jaundice and dilated CBD → cholestasis is present - BUT bile acids are still being synthesized and secreted (jaundice indicates obstruction, not hepatic failure) - Bile acid deconjugation occurs normally in the colon - The problem is **enzyme deficiency**, not bile acid availability ### Differential Features: Pancreatic vs. Hepatic Steatorrhoea | Feature | Pancreatic Insufficiency | Biliary Obstruction | |---------|--------------------------|---------------------| | **Pancreatic enzymes** | ↓↓ Lipase, amylase | Normal or mildly ↑ | | **Bile acids** | Normal | ↓ (if cholestasis) | | **Stool fat** | Due to undigested fat | Due to impaired emulsification | | **Fecal chymotrypsin** | Absent | Present | | **Response to pancreatic enzyme replacement** | Resolves steatorrhoea | No improvement | **Clinical Pearl:** The markedly elevated lipase (2400 U/L) and amylase (1200 U/L) indicate acute pancreatitis superimposed on chronic obstruction, further reducing enzyme secretion capacity. ### Why This Patient Has Steatorrhoea - Pancreatic head mass obstructs the pancreatic duct - Acinar cells cannot secrete lipase and colipase - Dietary triglycerides are not hydrolyzed - Fat passes into the colon unabsorbed → steatorrhoea - The jaundice is from biliary obstruction, not from impaired fat absorption [cite:Guyton & Hall Textbook of Medical Physiology Ch 64]