A 62-year-old man who underwent truncal vagotomy with gastrojejunostomy five years ago has chronic bloating, foul belching, intermittent watery diarrhoea and 6 kg weight loss. Symptoms previously resolved completely during a two-week antibiotic course for a dental infection. Which investigation best confirms the suspected diagnosis?

• A 72-hour faecal fat estimation
• B Faecal calprotectin measurement
• C Schilling test corrected by intrinsic factor
• D Hydrogen breath test showing an early peak within 90 minutes of glucose ingestion ✓

Explanation

Stasis in the afferent limb after gastrojejunostomy permits bacterial overgrowth that deconjugates bile salts and consumes nutrients, giving steatorrhoea and D12 deficiency. A carbohydrate challenge is fermented early, producing a hydrogen peak before substrate reaches the colon, which distinguishes SIBO from colonic fermentation. Response to antibiotics supports the diagnosis, and faecal calprotectin would remain normal because there is no mucosal inflammation.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.