Factitious diarrhea detected by measurement of stool osmolality

Patients with chronic unexplained diarrhea present a diagnostic and therapeutic challenge. Many disorders can cause chronic diarrhea, but despite extensive evaluation the cause may remain unknown. Surreptitious abuse of laxatives¹ and ingestion of drugs whose laxative properties are not recognized² are leading causes of chronic diarrhea in patients referred to university hospitals for evaluation³,⁴. Factitious diarrhea has traditionally been diagnosed by evaluating stools for laxatives. We recently studied two patients with chronic unexplained diarrhea who were found to have diluted their stool samples. Dilution was suspected when the measured stool osmolality was found to be considerably lower than.