mrcem2-0753

A 35-year-old woman presents with watery diarrhea that has been present since her return from a hiking trip in Peru 8 weeks ago. She has also experienced abdominal cramps and bloating and excessive gas. Stool cultures were done, which came back negative. She was referred to a gastroenterologist and had a small bowel tissue biopsy, which showed subtotal villous atrophy.

What is the SINGLE most suitable next step in management?