Hypersensitivity to Visceral and Cutaneous Pain in the Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is one of the most common gastrointestinal illnesses and is characterized by altered visceral perception. Previous studies in IBS have failed to demonstrate altered somatic or cutaneous perception. The aims of the study were to determine whether IBS patients have visceral hypersensitivity and cutaneous heat-induced hyperalgesia restricted to lumbosacral dermatomes, consistent with a localized segmental mechanism. Twelve patients (ten women, two men) with IBS and 17 control subjects (13 women, four men) rated pain intensity and unpleasantness to distension of the rectum (35, 55 mmHg) and thermal stimulation (45, 47 degrees C) of the hand and foot. Patients with IBS demonstrated cutaneous allodynia/hyperalgesia to thermal pain applied to the hand and foot. The cutaneous hyperalgesia was pronounced in the lower extremity yet present in the upper extremity to a lesser extent. Psychological testing revealed the IBS patients report more state anxiety and a greater number of somatic symptoms that significantly correlated with most of the pain measures. However, they did not differ from controls on several personality trait measures. These results suggest that patients with IBS have visceral hyperalgesia and cutaneous hyperalgesia that is distributed over a considerable rostral-caudal distance yet optimally expressed in lumbosacral dermatomes. This distribution is consistent with patterns of spinal hyperexcitability observed in experimentally induced persistent pain conditions.