On the role of bile acids in chronic diarrhoea

Abstract: Bile acids which promote lipid absorption are actively reabsorbed in the distal ileum. Bile acid malabsorption (BAM) and microscopic colitis (lymphocytic and collagenous) are both associated with chronic watery diarrhoea. The aims were to study: 1) the role of bile acids in collagenous and lymphocytic colitis, 2) the correlation between BAM and steatorrhoea in patients with chronic diarrhoea 3) bile acid absorption after a standardized resection of 55-70cm of the ileum leaving the distal 40cm intact. Patients with chronic diarrhoea underwent the 75SeHCAT test and a clinical work-up including colonoscopy. All patients recorded their symptoms. Faecal fat excretion was measured in 94 patients. Patients with microscopic colitis were treated with a bile acid binder. Collagenous colitis patients were reinvestigated after a median time of 4.2 years. Correlations between 75SeHCAT values, histopathology and symptoms were calculated. Patients operated on with a continent urinary diversion underwent the 75SeHCAT test. Twenty-nine healthy controls underwent the 75SeHCAT test.BAM was present in 44% of collagenous colitis patients and persisted in 32% at follow-up. BAM was uncommon in lymphocytic colitis but the median retention was significantly lower than in the control group. Bile acid binders were effective in >70% with collagenous colitis and in >40% with lymphocytic colitis. Histopathology improved in the long-term course of collagenous colitis in those who had stopped bile acid binder treatment and was unchanged in those with maintained treatment although symptoms were comparable. Ileum was normal irrespective of BAM. 75SeHCAT retention decreased from 32% to 17% after the ileal resection. No correlation between 75SeHCAT retention and faecal fat excretion was found. Patients with BAM had more frequent bowel movements and looser stool consistency compared with those without bile acid malabsorptionConclusions: BAM is a permanent finding in one third of patients with collagenous colitis. Absorption of bile acids is disturbed in both collagenous and lymphocytic colítis. Bile acid binders are effective in many patients with microscopic colitis. BAM and collagenous colitis are associated but presumably independant diseases. The 75SeHCAT value can not predict occurrence of steatorrhoea. BAM worsen the symptoms in chronic diarrhoea. The distal 40cm of the ileum is not enough to preserve normal absorption of bile acids