Compliance, tone and sensitivity of the rectum in different subtypes of irritable bowel syndrome

Irritable bowel syndrome (IBS) consists of various subtypes. It is not known whether these subtypes share a common pathophysiology. Evaluation of motor and sensory function of the rectum using a barostat may help to explore a common pathophysiological background or differences in pathophysiology in subtypes of IBS. We have evaluated compliance, tone and sensitivity of the rectum, in both fasting state and postprandially, using a computerized barostat in 15 patients with diarrhoea-predominant IBS (IBS-D), 14 patients with constipation-predominant IBS (IBS-C) and compared the results with those obtained in 12 healthy controls. Rectal compliance as calculated over the steep part of the pressure-volume curve (17-23 mmHg) was decreased in both IBS groups (IBS-D 8.0 +/- 1.4 mL mmHg (-1) ; IBS-C 5.6 +/- 1.1 mL mmHg (-1) ) compared with controls (24.7 +/- 3.5 mL mmHg (-1) ). The perception of urge was increased only in IBS-D patients, whereas pain perception was significantly increased in both IBS groups. Spontaneous adaptive relaxation was decreased in IBS-D patients. Postprandially, rectal volume decreased significantly in the controls and in IBS-D patients, but not in IBS-C patients. In conclusion, both rectal motor and sensory characteristics are different between IBS-D and IBS-C patients. Therefore, testing of rectal visceroperception, adaptive relaxation and the rectal response to a meal may help distinguish groups of patients with different subtypes of irritable bowel syndrome.