Quantitation of hypertensive nephrosclerosis on an objective rational scale of measure in adults and children.

The development of a precise, mathematical relationship between blood pressure and renal microvascular abnormalities would be highly desirable. Such a relationship would require that abnormalities be quantitative on a rational scale. The dominant abnormality in nephrosclerosis occurs in arcuate and cortical arteries of 50 to 400 micron outer diameter. This abnormality consists of acquired inner layers of fibroplastic tissue accompanied by variable fibrosis or withering of the preexisting vessel wall. It is this pathologic variable of interest, the amount of fibroplasia, that can be measured by its thickness in a direction perpendicular to the arterial axis. A method for quantitating the fibroplasia is described. Use of this method in a series of 93 autopsies suggests two tentative conclusions. The outer diameter of 141 micron marks the size of artery in which fibroplasia best correlates with blood pressure. The linear function, mean blood pressure = 1.60 X microvascular lesions +79.7, with correlation coefficient 0.698, governs a relationship similar at all ages. This relationship can be used to compute expected blood pressure from measurements of microvascular abnormalities in kidneys obtained at autopsy. Because all ages include ages 14 to 21 years, the observations imply that the initial tissue changes of hypertensive disease occur early in life.