The term gastrointestinal tract diseases refer to a variety of conditions and diseases that affect the gastrointestinal tract.

Bile acids malabsorption (BAM) represents a common but frequently under investigated cause of chronic diarrhea whose prevalence estimate is approximately 1% in the general population [2,3,4]. In addition, it has been reported that approximately 25–33% of unexplained chronic diarrhea is due to BAM [3] and one third of patients treated for irritable bowel syndrome diarrhea-predominant (IBS-D) have idiopathic BAM [26].

Due to a disruption of the reabsorption of bile acids (BA) in the terminal ileum, the BA concentration in the colon increases. This leads to increased motility of the colon and increased water and electrolyte excretion, resulting in diarrhea. Since reabsorption is very effective under physiological conditions, altered BA levels in stool during diarrhea indicate a functional disorder in the terminal ileum, as in Crohn's disease (ileitis terminalis). In addition to Crohn's disease, there are many other intestinal diseases that may lead to this clinical presentation [4-5].