Diagnosing Bile Acid Diarrhoea Diagnosing Bile Acid DiarrhoeaChronic diarrhoea is estimated to affect up to 5% of the population. Bile acid diarrhoea (BAD) is a common form of chronic diarrhoea caused by inadequate reabsorption of bile acid produced as part of the fat digestion process. Reabsorption  can be  perturbed  through  disease,  surgical  removal  of  a  length  of  bowel  or through  defects  in certain  regulatory  proteins. Diagnosis currently requires patients to swallow a capsule of radioactive selenium-75 tagged to homochlorotauric acid.