ISCHEMIC NATURE OF ANAL-FISSURE

Microvascular perfusion of the anoderm was assessed by laser Doppler f lowmetry in 27 patients with anal fissure. Anal pressure was recorded simultaneously. Both measurements were repeated 6 weeks after lateral internal sphincterotomy and compared with those obtained from 27 contr ols. Mean(s.d.) maximum anal resting pressure was significantly higher in those with a fissure than in controls (121.07(24.48) versus 68.78( 16.97) mmHg, P<0.001). Anodermal blood flow at the fissure site was si gnificantly lower than at the posterior commissure of the controls (0. 46(0.20) versus 0.76(0.28) V, P<0.001). The fissure healed in 24 patie nts within 6 weeks of sphincterotomy. In these patients a significant pressure decrease was noted (35 per cent) which was accompanied by a c onsistent rise in blood flow (65 per cent) at the original fissure sit e. The increased internal sphincter tone in patients with a fissure re duces anodermal blood flow at the posterior midline. Reduction of anal pressure by sphincterotomy improves anodermal blood flow at the poste rior midline, resulting in fissure healing. These findings provide evi dence for the ischaemic nature of anal fissure.