RELATIONSHIP BETWEEN ANAL PRESSURE AND ANODERMAL BLOOD-FLOW - THE VASCULAR PATHOGENESIS OF ANAL FISSURES

PURPOSE: The aim of this study was to investigate the relationship bet ween anal pressure and anodermal blood flow. METHODS: We performed Dop pler laser flowmetry of the anoderm combined with anorectal manometry in 178 subjects (87 males and 91 females; median age, 55 (range, 17-87 ) years). This group consisted of 31 healthy volunteers, 23 patients w ith fecal incontinence, 17 patients with hemorrhoids, and 9 patients w ith anal fissure. The remaining 98 patients had other colorectal disor ders. In 16 controls we examined anodermal blood flow in the four quad rants of the anal canal. RESULTS: Perfusion of the anoderm at the post erior midline was significantly lower than in the other three segments of the anal canal (posterior midline: 0.74 +/- 0.26 V; left lateral s ide: 1.68 +/- 0.81 V; right lateral side: 1.57 +/- 0.52 V; anterior mi dline: 1.48 +/- 0.69 V, P< 0.001). In the overall group, we found a si gnificant correlation between maximum anal resting pressure and anoder mal blood flow at the posterior midline (r = -0.616, P < 0.001). In th e nine patients with chronic anal fissure, the mean maximum anal resti ng pressure was 125 +/- 26 mmHg, which was significantly higher than i n patients with hemorrhoids (82 +/- 15 mmHg), controls (66 +/- 19 mmHg ), and patients with fecal incontinence (42 +/- 14 mmHg, P < 0.001), w hereas the blood flow at the base of the fissure was significantly low er (0.43 +/- 0.10 V vs. 0.57 +/- 0.19 V vs. 0.75 +/- 0.26 vs. 1.03 +/- 0.34 V). In ten patients we also studied the influence of anesthesia on both anal pressure and anodermal blood flow. During the administrat ion of anesthesia, anal pressure dropped from 63 +/- 21 mmHg to 32 +/- 15 mmHg (P < 0.001), whereas anodermal blood flow at the posterior mi dline increased from 0.79 +/- 0.22 V to 1.31 +/- 0.35 V (P < 0.001). C ONCLUSION: Anodermal blood flow at the posterior midline is less than in the other segments of the anal canal. The perfusion of the anoderm at the posterior commissure is strongly related to anal pressure. The higher the pressure, the lower the flow. Our findings support the hypo thesis that anal fissures are ischemic ulcers.