Renal macrostructure and cortical circulation in hypertension assessed by dynamic computed tomography

The aim of this study was to assess the macrostructure of the kidney and the grade of heterogeneity in renal cortical circulation in the early stages of essential hypertension. The subjects consisted of 84 patients (<50 years old) who underwent dynamic computed tomography (CT) because of various abdominal diseases and who had no serious hemodynamic abnormalities. The volumes of the whole kidney, cortex, and medulla were measured with the program installed in the CT instrument. In dynamic CT under appropriate conditions, the CT number of each pixel (image element) reflects the blood volume in the pixel. The means and standard deviations were calculated from the CT numbers within the renal cortex. The coefficient of variation (CV) of CT numbers was used as the index of the heterogeneity of renal cortical circulation. The volume ratio of cortex/medulla was significantly (P < .01) smaller in the hypertensive patients (0.80 +/- 0.03 (mean +/- SE)) than in the normotensive subjects (0.92 +/- 0.03). The CV was significantly (P < .01) greater in the hypertensives (n = 23, 0.124 +/- 0.008) than in the normotensives (n = 61, 0.106 +/- 0.003). There was a significant correlation (r = -0.391, P < .001) between the CV of CT numbers and the volume ratio of cortex/medulla, and the relationship between the two variables was independent of other variables. These results suggest that the heterogeneity of renal cortical circulation is increased in the early stages of essential hypertension and is related to changes in renal macrostructure.