Patients with irritable bowel syndrome-diarrhea (IBS-D) and bile acid diarrhea (BAD) have increased colonic permeability, which may contribute to an increase in colonic secretion, according to a study in Gastroenterology.

Investigators compared mucosal permeability in patients with IBS-D without BAD and in those with BAD, as well as with normal healthy volunteers.

The participants were tested in the morning for fasting serum 7αC4, fibroblast growth factor-19 (FGF-19), and the percentage of primary bile acids (1°BA) in a random stool sample. BAD was defined as serum 7αC4 >52 ng/mL.


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After an overnight fast, the participants consumed 100 mg 13C-mannitol and 1 g of lactulose in a 240-mL glass of water. They then fasted for 2 hours and received an additional 500 mL of water 30 minutes afterward. Urine samples were collected from 0 to 2, 2 to 8, and 8 to 24 hours.

A total of 205 patients with IBS-D (44 with BAD [median age, 46 years; 84% women] and 161 without BAD [median age, 37; 77% women]) and 60 NHVs (median age, 45.5 years; 50% women) were included. Patients with IBS-D with BAD had a higher body mass index (BMI) (P =.001) compared against patients without BAD.

A significantly higher urinary excretion of 13C-mannitol was observed between 0 and 2 hours in NHVs compared against patients with IBS-D without BAD, and no difference was found between those with IBS-D with and without BAD. No significantly greater urinary excretion of 13C-mannitol occurred in the IBS group from 2 to 8, 8 to 24, and 2 to 24 hours compared with NHVs (P =.86). A higher urinary excretion of 13C-mannitol was observed in patients with IBS-D with BAD vs those with IBS-D without BAD at 2 to 8, 8 to 24, and 2 to 24 hours (all P <.05).

Urinary excretion of lactulose was significantly greater among NHVs compared against patients with IBS-D. No significant difference was found between the groups at 2 to 8 hours, though urinary excretion was significantly greater in patients with IBS-D with BAD vs those with IBS-D without BAD between 8 to 24 hours and 2 to 24 hours. No significant difference was found between NHVs and patients with IBS-D regarding urinary excretion between 8 to 24 hours and 2 to 24 hours.

Urinary 13C-mannitol at 2 to 24 hours was associated with serum 7αC4 levels (P =.0443) and percentage 1°BA (P =.0372) in all IBS-D patients.

“Since IBS-D patients with BAD had significantly higher BMI than patients without BAD, future studies are needed to determine whether obesity could be a potential confounder in the relationship between BAD and permeability,” the study authors concluded.

Reference

Magnus Y, BouSaba J, Sannaa W, et al. Bile acid diarrhea is associated with increased intestinal permeability compared to irritable bowel syndrome-diarrhea. Gastroenterol. Published online December 16, 2021. doi: 10.1053/j.gastro.2021.12.243