Sensitization to painful distention and abnormal sensory perception in the esophagus

The mechanism of abnormal esophageal sensory perception in patients with unexplained chest pain is unknown. The aim of this study was to test the following two hypotheses: (1) similar to cutaneous nociceptors, esophageal stretch receptors can be sensitized by a noxious chemical stimulus, and (2) patients with esophageal chest pain have sensitized receptors.

Twenty-five patients with noncardiac chest pain underwent esophageal manometry, provocation tests, and 24-hour pH monitoring. Eleven patients had positive and 14 had negative results of esophageal provocation tests. Esophageal perception and pain thresholds for balloon stretch (in milliliters) and electrical stimulation (in milliamperes) were determined in patients and 7 healthy controls performed before and after randomized, double-blind esophageal perfusion with normal saline or 0.1N HCl.

The basal balloon pain threshold was lower in patients with positive results of esophageal tests than in either those patients with negative results of esophageal tests or controls (P < 0.05). After acid perfusion, balloon perception and pain thresholds decreased in patients with negative results of esophageal tests (P < 0.05) and in controls (P < 0.05) but not in patients with positive results of esophageal tests. No change occurred after saline perfusion nor in electrical pain thresholds in any group after the perfusion of either fluid.

In patients with negative results of esophageal tests and in controls, the pain threshold to balloon distention is lowered by acid. The lack of such effect in patients with positive results of esophageal tests implies that pain receptors may already be sensitized.