TABLE 2.

Classification of bile acid malabsorption (BAM)

Classification of BAM	Etiology
Type 1   Ileal dysfunction (secondary BAM)	Ileal Crohn disease, ileal resection Results in failure to reabsorb BAs at the distal ileum leading to BA spillover into colon
Type 2   Idiopathic BAM/primary bile acid diarrhea	Unknown cause No consistent inherited abnormality in transporter proteins Mechanisms may arise from defect in negative feedback (FGF19) regulation in the synthesis of BAs, leads to overproduction of BAs
Type 3   Other conditions	Postcholecystectomy, postvagotomy, celiac disease, bacterial overgrowth, pancreatic insufficiency (chronic pancreatitis and cystic fibrosis) May involve alterations in small intestinal motility, altered BA cycling, or composition of ileal contents

Adapted from reference 27. BA Bile acid; FGF Fibroblast growth factor