Which is the best distension protocol to study rectal sensitivity in the irritable bowel syndrome?

To evaluate any differences in rectal distension perception between healthy subjects and patients with irritable bowel syndrome (IBS) according to an isobaric distension protocol (progressive or phasic).

10 healthy subjects and 41 patients with IBS (Rome II criteria). Rectal distension was performed using a barostat connected to a 500 mL bag, and a progressive distension protocol (continuous distension at a rate of 0.36 mmHg/sec) was compared to phasic distension protocol (distensions for 60 sec with 4 mmHg increases separated by 0 mmHg pressures during 60 sec). Perception was evaluated using three descriptive scales of 7 categories each for perception type, intensity, and affectivity. Perception thresholds were assessed.

No significant differences in any perception thresholds were found between control subjects and IBS patients using a progressive distension protocol. Differences in the perception of inconvenient distension and maximum tolerable distension were encountered with the phasic distension protocol. Uncomfortable distension thresholds below those of controls were found in 48.8% of patients with IBS when a phasic distension protocol was used, versus only 9.7% with a progressive protocol.

Hypersensitivity in patients with IBS is mainly seen with the use of phasic distension isobaric protocols for affective negative perceptions.