Rectal wall contractility in healthy subjects and in patients with chronic severe constipation

The aim of this study was to identify differences in rectal wall contractility between healthy volunteers and patients with chronic severe constipation.

Whether motor function of the rectum contributes to slow-transit constipation is unknown. Measurements of rectal contractility have been performed traditionally with perfused catheters or microtransducers. The rectal barostat is a new technique that quantifies the volume of air within an infinitely compliant intrarectal bag maintained at constant pressure; decreases in bag volume therefore reflect increases in rectal muscular contractility (tone). Increases in volume reflect decreased contractility.

Fifteen healthy volunteers (ten women and five men; mean age, 36 years) and eight patients (seven women and one man; mean age, 44 years) were studied. Barostat recordings were made for 1 hour before and after a meal. Randomly, neostigmine (0.5 mg) or glucagon (1 unit) was then given intravenously. After 1 hour, the other medication was given.

The fasting rectal volume was similar in the patient and control groups (113 +/- 7 mL vs. 103 +/- 4 mL, respectively; p > 0.05). Compared with controls, constipated patients had a significantly lower reduction in rectal volume after a meal (constipated, 35 +/- 8% vs. controls, 65 +/- 7%; p < 0.05) and after neostigmine administration (constipated, 39 +/- 6% vs. controls, 58 +/- 6%; p < 0.05). Moreover, constipated patients had a smaller increase in rectal volume after glucagon administration than did controls (28 +/- 6% vs. 64 +/- 18%, respectively; p < 0.05.

Changes in rectal wall contractility in response to feeding, a cholinergic agonist, and a smooth muscle relaxant were decreased in constipated patients. These findings suggest that an abnormality of rectal muscular wall contractility is present in constipated patients.