A 70-year-old man with CKD stage 3 (eGFR 40 mL/min) presents with epigastric pain. Serum amylase is 480 U/L (3× upper normal). Lipase is 120 U/L (upper normal 60). Urine amylase is low. Contrast CT shows no pancreatic inflammation. Which is the MOST likely explanation for the elevated amylase?
- A Acute pancreatitis
- B Intestinal perforation
- C Macroamylasaemia ✓
- D Parotitis
Correct answer: C. Macroamylasaemia
Explanation
Macroamylasaemia is a benign condition where amylase forms large complexes with immunoglobulins, reducing renal clearance and causing elevated serum amylase with low urine amylase. The amylase-to-creatinine clearance ratio is low (<1%). Distractor A is ruled out by normal CT and only mildly elevated lipase. Distractor B would cause elevated amylase but with peritonitis signs. Distractor D would show parotid swelling and normal urine amylase.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.