A 32-year-old woman reports bloating, cramps, and flatulence beginning 45 minutes after drinking milk. After an oral lactose load, her breath hydrogen rises from 6 ppm to 34 ppm within 90 minutes. What does this result indicate?
- A Normal lactose digestion, symptoms are functional
- B Small intestinal bacterial overgrowth
- C Lactose malabsorption due to lactase deficiency ✓
- D Pancreatic exocrine insufficiency
Explanation
Undigested lactose reaching the colon is fermented by bacteria, releasing hydrogen that is absorbed into blood and exhaled. A rise in breath hydrogen of more than 20 ppm above baseline within the test period confirms lactose malabsorption, matching her symptom pattern. Small intestinal bacterial overgrowth produces an early hydrogen peak within 30 minutes before the substrate reaches the colon, not a delayed sustained rise. Pancreatic insufficiency causes fat malabsorption with steatorrhea and is assessed by fecal elastase, not hydrogen breath testing.
Reference: Sleisenger and Fordtran's Gastrointestinal and Liver Disease, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.