Abstract

Background: A subset of patients with the irritable bowel syndrome (IBS) has an increased number of mast cells (MCs) in the colonic mucosa. Psychological factors are believed to contribute to the course of IBS. Aims: To examine associations between fatigue, depression and MCs of the colonic mucosa in IBS.

Methods: Colonic biopsies were taken from 50 Rome II IBS patients, 21 healthy controls and 11 depressed/fatigued patients without IBS. The cellularity of the lamina propria referred as the number of inflammatory cells per high power field (hpf) through a 400x microscope. The Fatigue Impact Scale (FIS) and the short form Beck Depression Inventory (BDI) evaluated the severity of fatigue and depression.

Results: IBS had a significant increase of the cellularity of the lamina propria compared to controls or to depressed patients (94.5[48-110] vs 68[58-82] and 78[87-90] cells per hpf, p=0.005 and p=0.05 respectively), in particular of MCs (9.3[5.6-11.7] vs 4.0[2.7-6.8] and 4.3[2.8-7.8] cells per hpf, p=0.001 and p=0.005 respectively). Both FIS and BDI scores were significantly higher in IBS than in controls or in depressed patients (p<0.001). In IBS, the FIS score correlated significantly with the cellularity of the lamina propria (r=0.51, p<0.0001) and MCs (r=0.64, p<0.0001). In IBS, the BDI score correlated significantly with MCs (r=0.29, p=0.03).

Conclusions: Elevated MCs counts are a key feature of the low grade inflammatory infiltrate in the caecal mucosa of IBS. Fatigue and depression are associated with mucosal cell counts, in particular MCs suggesting that psychological factors are associated to the low-grade inflammatory infiltrate in IBS.