Introduction Bile acid malabsorption (BAM) is a common cause of chronic secretory diarrhoea via poorly characterised mechanisms. The aim of this study was to determine if histological abnormalities in colonic mucosa are linked to BAM in patients with chronic diarrhoea.
Methods During a 6-year period 264 patients were investigated with SeHCAT for chronic diarrhoea and their retention values recorded (≤8% = positive result; ≥16% = negative result). Colonic biopsies and histological analysis were available in 150 (57%). The patients were categorised as: Group 1: terminal ileum Crohn's disease, (pre or post resection) n=51. Group 2: Idiopathic BAM (including patients with diarrhoea predominant IBS) n=159. Group 3: BAM secondary to other gastrointestinal disease n=51; of which cholecystectomy (n=37), coeliac disease (n=1), chronic pancreatitis (n=1), bacterial overgrowth (n=2), diabetes (n=4) and other gastrointestinal surgeries (n=6). Group 4: terminal ileum disease plus cholecystectomy n=3.
Results A histological abnormality was present in 29% (n=16/56) of the patients with positive SeHCAT, vs 23% (n=17/74) of the patients with negative SeHCAT (p=0.318, two-tailed Fisher's exact test). Similarly, 30% (n=6/20) of the patients with equivocal SeHCAT results (8%–16% retention) had histological abnormalities. As expected, the highest prevalence of these abnormalities was noted in groups 1 and 4, the subjects with Crohn's disease, regardless of the presence of BAM. Abnormalities were noted in descriptive terms and included colitis (n=4), chronic inflammation (n=5), cryptitis (n=4), mild non-specific inflammation (n=11), moderate non-specific inflammation (n=5), polyps (n=2), ulceration (n=6) and active inflammatory bowel disease (n=2). 30% (n=8/27) of positive SeHCAT with idiopathic BAM (group 2) had abnormalities on histology compared with 19% (n=10/52) who had negative SeHCAT in group 2, which was again a non-significant difference (p=0.397, two-tailed Fisher's exact test). The 7% (n=2/28) of patient in group 3 with histological abnormalities also had negative SeHCAT results.
Conclusion This retrospective study indicates that colonic histological abnormality is non-specific and coincidental to the presence of bile acid malabsorption in patients with chronic diarrhoea. It is unlikely to be relevant to the mechanism of diarrhoea which is probably non-inflammatory. This might be further studied in the future using faecal markers of inflammation in these patients.
Competing interests None declared.
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