Functional dyspepsia and irritable bowel syndrome: is there a common pathophysiological basis?

Abstract

Objectives: Alterations of mechanosensitive thresholds occur in a subset of patients with functional dyspepsia and irritable bowel syndrome (IBS). However, symptoms associated with these two conditions frequently overlap. It is not known how often subjects with and without symptom overlap have abnormal intestinal sensory thresholds. Our objective was to assess the pattern of symptoms and small intestinal sensory thresholds in patients with functional disorders.

Methods: We studied 157 consecutive patients who had undergone extensive diagnostic work-up to exclude organic disease. Abdominal symptoms were assessed with a validated instrument, and patients were categorized as having functional dyspepsia, IBS, or both. With a barostat device, we tested small intestinal mechanosensitive function in 22 randomly selected patients from this population (with functional dyspepsia, IBS, or both) and 22 healthy controls.

Results: Sixty-seven patients (43%) reported simultaneous symptoms of functional dyspepsia and IBS, whereas symptoms of functional dyspepsia or of IBS alone occurred in 68 (43%) and 22 (14%) patients, respectively. Thresholds for first perception and maximum tolerated pressure (mm Hg +/-SD) were significantly lower in patients (21.0 +/- 2.0 and 31.0 +/- 1.0) than in controls (32.0 +/- 1.8 and 39.0 +/- 0.9, p < 0.001). However, thresholds for first perception and maximum tolerated pressure did not differ (p > 0.6) in patients with functional dyspepsia alone (20.1 +/- 3.2 and 28.9 +/- 2.5, n = 9), functional dyspepsia and concomitant IBS (19.9 +/- 2.7 and 30.7 +/- 2.2, n = 8), or IBS alone (23.5 +/- 2.3 and 33.3 +/- 3.0, n = 5).

Conclusions: Small intestinal mechanosensitive pathways are disturbed in patients with functional dyspepsia and IBS. Differences in the pattern and localization of symptoms probably do not reflect differences in small intestinal sensory thresholds. Functional dyspepsia and IBS cannot be distinguished on the basis of altered small intestinal sensory thresholds.