Renal Function in the Separate Kidneys of Man. Ii. Hemodynamics and Excretion of Solute and Water in Essential Hypertension *†

Abstract

The frequent coincidence of hypertension and renal disease is universally recognized, and it has been proposed that all hypertensive disease, including essential hypertension, somehow or other has its origin in the kidneys. This interpretation would be favored by the demonstration of one or more defects in renal function early in the course of essential hypertension. Although the presumed causal defect may, of course, be bilateral, the only feasible approach to this problem at the present time appears to lie in the functional comparison of the separate kidneys, which might reveal some subtle impairment not evident in bilateral studies.In 1941, Chasis and Redish (1) examined 21 patients with essential hypertension by conventional methods and found that both kidneys were, grossly at least, equally affected. At that time, no data were available on the natural variability of function in the two kidneys of normotensive individuals. We have extended these observations by examining function in the separate kidneys, by ureteral catheterization, in 21 normotensive and 50 additional hypertensive subjects with respect to filtration rate, renal plasma flow, TmPAH, sodium, total solute and water excretion.In the preceding paper (2) compares the incidence of functional disparity in patients with essential hypertension to our normotensive group and also describes patterns of renal functional impairment which have been derived from correlating disparities in sodium and solute excretion. METHODSObservations were made in 50 patients with essential hypertension selected from the wards and outpatient clinic of the Third (New York University) Medical Division of Bellevue Hospital. Patients were chosen with minimal retinal and cardiac abnormalities according to heart X-ray, electrocardiogram and funduscopic examination, and the majority were judged to be in the early stage of essential hypertension. Patients known or suspected of having gross renal arterial or urologic disease were excluded.The group consists of 43 female and 7 male patients between the ages of 14 and 65 years. All patients were maintained on the regular hospital diet. Fluids were withheld for 15 hours and the test was performed in the morning with the subjects in a fasting state.Ureteral catheterization and the subsequent determination of filtration rate (GFR), renal plasma flow (RPF), TmPAH, and sodium, solute and water excretion (UN.V, Uo.mV and V) by the separate kidneys were performed according to the technique and methods outlined in the preceding paper (2). Calculations were made of sodium excretion fraction (EFNS), solute excretion fraction (EFo,m) and the per cent contribution of sodium and its attendant anion to the total urine osmolality (UNai/Uo.m X 100).The data were examined to determine the incidence of disparities for each function according to the normal limits of difference between the two kidneys as established in the normotensive group. RESULTSValues for GFR, RPF, TmPAH, V, UNa, Uosm and derived data in the separate kidneys of 50 hypertensive pat...

Responses of the stenosed and contralateral kidneys to [Sar1, Thr8] AII in human renovascular hypertension.

“…These figures are admittedly approximate, as previous measurements of split renal function in essential hypertension have indicated that renal function may not be always symmetric. 18 Nonetheless, these figures do reflect a marked discrepancy in function between stenotic and contralateral kidneys and provide an explanation of remarkably well-preserved overall function despite unilateral ischemic renal atrophy.…”

Renal Function in the Separate Kidneys of Man. I. Hemodynamics and Excretion of Solute and Water in Normal Subjects *

“…Per cent = -X 100, Uosm (1) where UNS is the urine sodium concentration in milli-equivalents per liter of urine, and Uo.m is the urine solute concentration in milliosmoles per kilogram of water. 2 Excretion fraction (EF) of sodium or total solute is the percentage of the filtered load excreted in the urine: It is conventional to define "normality" by recourse to probability theory and the use of parametric statistical analysis (mean + standard deviation), but the parametric method has the disadvantage that it is applicable only when the frequency distribution curve approaches the symmetrical or Gaussian form.…”

Asymmetry of Renal Blood Flow in Patients With Moderate to Severe Hypertension

“…From sequential renal blood flow measurements in the same kidney in patients with essential hypertension, Hollenberg et al 15 observed differences in flow that were comparable to those between the 2 kidneys as found by Baldwin et al 13 Compared with normotensive controls, renal blood flow in patients with essential hypertension exhibited a 2.2-fold greater variability, which the authors attributed to sinusoidlike oscillations in renal blood flow with a similar cycle length (about 40 sec), but increased maximal amplitude. 15,16 It can be concluded from their experiments that the total variability of blood flow in each kidney will randomly result in significant flow differences between both kidneys.…”

“…In 6 of the 15 essential hypertensives, differences in flow between kidneys exceeded 25%, whereas asymmetry was not found in the normotensives. In a study performed by Baldwin et al, 13 selective clearances of inulin and p-aminohippurate were used to investigate subjects who were judged to be in the early stage of essential hypertension. They defined disparity of effective renal plasma flow (ERPF) as being abnormal when it exceeded the 90th percentile of differences between two kidneys in subjects with normotension and found this to be present in 19 out of 36 patients.…”