A 26-year-old woman reports bloating, cramps and loose stools after drinking milk since adolescence. She tolerates aged cheese and curd well. Hydrogen breath test after 25 g lactose load shows a rise in breath hydrogen of 25 ppm above baseline within 90 minutes. What does this result indicate?
- A Small intestinal bacterial overgrowth
- B Normal lactose absorption
- C Lactase deficiency with colonic bacterial fermentation of unabsorbed lactose ✓
- D Fructose malabsorption
Correct answer: C. Lactase deficiency with colonic bacterial fermentation of unabsorbed lactose
Explanation
A rise in breath hydrogen of more than 20 ppm above baseline after a lactose load indicates carbohydrate malabsorption due to lactase deficiency, with hydrogen generated by colonic bacterial fermentation. Tolerance of curd and aged cheese fits lactose intolerance because fermentation reduces lactose content. SIBO produces an early hydrogen peak within 30 minutes, before the colonic phase, which is absent here.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.