NORMAL CUTANEOUS MICROCIRCULATION IN GAITER ZONE (ULCER-SUSCEPTIBLE SKIN) VERSUS NEARBY REGIONS IN HEALTHY-YOUNG ADULTS

Skin just proximal to the medial malleolus ('gaiter' zone) is the usual site for venous ulceration in later life, whereas shin and dorsum of the foot are generally unaffected. We studied the microcirculation of these regions in 6 healthy young adults to see whether any premorbid, constitutional differences in microvascular physiology or anatomy exist between local leg sites even in normal subjects. Capillary density was assessed by capillaroscopy (native and fluorescein) and local flow by laser Doppler fluxmetry, in supine and upright positions and during reactive hyperaemia. Supine capillary densities in supra-medial malleolar skin (SMMS) averaged 31-38 mm(-2) (fluorescein and native count means, respectively) and was not statistically significantly different from those in the dorsum of the foot (36.0-36.2 mm(-2)) or shin 30-51 mm(-2)). Dependency did not alter the counts significantly, but the fluorescein transport time from antecubital vein to capillary increased by 16-69% (SMMS 40%). In the supine position, red cell flux in SMMS was only 42-43% of the flux in skin over the shin and dorsum of the foot (p < 0.04, 2-way analysis of variance) and cumulative reactive hyperaemia in SMMS was also less marked. Basal flux and reactive hyperaemia at all sites fell to closely similar levels in dependency (veni-arteriolar response). In relative terms, however, the posturally induced vasoconstriction was weaker in SMMS (flux reduction by 29% of supine value) than at other sites (reductions by 61-62% of supine value). The results showed that even in young healthy legs the cutaneous microcirculation is not physiologically homogeneous, raising the possibility that constitutional factors might influence the siting of overt pathology if chronic venous insufficiency develops in later life.