Alteration in visceral sensation locally at the site of presumed symptom origin in the gastrointestinal tract has been proposed as an important etiopathological mechanism in the so-called functional bowel disorders. Patients presenting with one functional gastrointestinal syndrome, however, frequently have additional symptoms referable to other parts of the gut, suggesting that enhanced visceral nociception may be a panintestinal phenomenon. We measured the sensory thresholds for initial perception (IP), desire to defecate (DD), and urgency (U) in response to rectal balloon distension, and the thresholds for initial perception and for discomfort in response to esophageal balloon distension in 12 patients with irritable bowel syndrome (IBS) and 10 patients with functional dyspepsia (FD), in comparison with healthy controls. As expected, IBS patients exhibited lower rectal sensory thresholds than controls (P < 0.0001), but in addition had significantly lower sensory thresholds for both perception and discomfort evoked by balloon distension of the esophagus (mean +/- SEM: 8.8 +/- 1.3 ml vs 12.1 +/- 1.5 ml (P < 0.05) and 12.2 +/- 1.4 ml vs 16.4 +/- 1.4 ml (P < 0.02) respectively. Patients with FD showed similarly enhanced esophageal sensitivity, with thresholds for perception and discomfort of 8.1 +/- 0.9 ml (P < 0.02), and 10.1 +/- 1.0 ml (p < 0.001), respectively, but were also found to have sensory thresholds for rectal distension similar to those observed in the IBS group, significantly lower than in controls: IP 45.0 +/- 17.6 vs 59.3 +/- 1.5 ml (P < 0.001), DD 98.0 +/- 17.9 vs 298.7 +/- 9.0 ml (P < 0.0001), U 177.2 +/- 25.4 vs 415.1 +/- 12.6 ml (p < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)