Fecal Occult Blood Test, Positive: What Study Next?

Results of upper and lower endoscopy are inconclusive. Your next step?

A 32-year-old woman presents with symptomatic anemia. A fecal occult blood test taken in the emergency room is positive. She undergoes an esophagogastroduodenoscopy (EGD) and colonoscopy, both of which are unrevealing. 

Which of the following studies should be performed next?