Laser Doppler flowmetry as a measure of extrinsic colonic innervation in functional bowel disease

Background--In functional disorders it is unknown whether disturbed functio n is due to an intrinsic gut abnormality or altered extrinsic innervation. Aims--To study whether measurement of mucosal blood flow could be used as a quantitative direct measure of gut extrinsic nerve autonomic activity in p atients with idiopathic constipation. Methods--Seventy two patients with idiopathic constipation and 26 healthy v olunteers had rectal mucosal blood flow measurements by a laser Doppler flo wmetry probe applied 10 cm from the anus. Measurements were made at rest an d after inhaled placebo and ipratropium 40 mu g. Results-Constipated subjects had lower baseline rectal blood flow than cont rols. Patients with slow transit had lower mucosal blood flow than normal t ransit. The number of retained markers on x ray was inversely correlated wi th blood flow. Ipratropium reduced blood how compared with placebo, reduced it less in constipated patients than controls, and reduced it less in pati ents with slow compared with normal transit. Constipated patients, not cont rols, showed a significantly attenuated RR interval (the interval between s uccessive R waves on the EGG) variability, and blood flow correlated with v agal function. Conclusions--Laser Doppler mucosal flowmetry is a gut specific, quantitativ e measure of extrinsic autonomic nerve activity. The technique has shown th at patients with idiopathic constipation have impaired extrinsic gut nerve activity, and this is more notable in those with slow transit. The degree o f slow transit correlates with the degree of impaired extrinsic innervation .