Bile acid modulation in lower functional gastrointestinal disorders with diarrhea or constipation. BA, bile acid; C4, 7-α-hydroxy-4-cholesten-3-one; CA, cholic acid; CDCA, chenodeoxycholic acid; DCA, deoxoycholic acid; FGF-19, fibroblast growth factor 19; FXR, farnesoid X receptor; IBAT, ileal bile acid transporter; LCA, lithocholic acid. [Reproduced in part from Vijayvargiya and Camilleri (79) with permission.]