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

Objective: The aim of this study was to identify differences in rectal wall contractility between healthy volunteers and patients with chronic severe constipation. Summary Background Data: 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. Methods: 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. Results: 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. Conclusions: 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.