Renal function in man during transition from hydropenia to water diuresis with superimposed mannitol load

Role of hypervolemia and renin in the blood pressure control of patients with pyelonephritis renal scarring

Patients with pyelonephritic renal scarring are at risk of developing renal failure and hypertension. We studied glomerular filtration rate (GFR), renal plasma flow (RPF), filtration fraction (FF), systolic (SBP) and diastolic (DBP) blood pressure, fractional sodium, potassium and phosphate excretion, peripheral renin activity (PRA), plasma aldosterone (p-Aldo), urinary albumin excretion (U-Alb) and urinary beta 2-microglobulin excretion (beta 2-M) in hydropenia and during transition to 3% volume expansion with isotonic saline infusion in 22 female patients with renal scarring due to pyelonephritis and 9 healthy controls. The patients had significantly lower GFR, higher SBP and higher PRA in hydropenia, but there was no significant difference in RPF, FF, DBP or p-Aldo. After volume expansion, SBP, DBP, PRA and p-Aldo were significantly higher in patients than in controls. Transition to 3% volume expansion was associated with a similar increase in SBP in both patients and controls, whereas DBP increased significantly more in the patients (p less than 0.01). Volume expansion resulted in a significant suppression of PRA and p-Aldo in both patients and controls. The patients with renal scarring had the same capacity to excrete sodium and water during transition to volume expansion as the healthy controls. The renin-aldosterone system seems abnormally activated and is probably more important than hypervolemia in the development of hypertension in this group of patients.

The effect of fluid deprivation, antidiuretic hormone and forced fluid intake on 51-Cr-EDTA clearance

The effect of fluid deprivation, antidiuretic hormone (DDAVP) and forced fluid intake on glomerular filtration rate (GFR) was studied in 41 healthy males by determining 51-Cr-EDTA clearance after a single bolus injection. GFR was the same on forced and on free fluid intake. A small, clinically insignificant decrease in GFR (-6.5%), compared to values on free fluid intake, was registered during the periods of fluid deprivation plus DDAVP. There seem to be no objections to combining a clearance study with a concentrating ability test when screening groups of subjects with normal or near normal GFR.

Effects of alpha 2-adrenergic blockade on renal hemodynamics in patients with insulin dependent diabetes mellitus

The role of renal alpha 2-adrenoceptors in the regulation of glomerular filtration and renal perfusion is unknown. We studied the effects of alpha 2-adrenergic blockade on renal hemodynamics in six patients with insulin-dependent diabetes mellitus (IDDM) and in six healthy subjects. At the basal state, glomerular filtration rate (GFR) was higher in IDDM although the difference from control levels was not statistically significant. Volume expansion, achieved by infusion of isotonic sodium chloride solution, during placebo infusion induced a significant drop in GFR in healthy subjects but not in IDDM patients. Infusion of the alpha 2-adrenoceptor antagonist idazoxan did not further modify the effect of volume expansion on GFR. Renal plasma and blood flow as well as filtration fraction were not significantly changed by volume expansion or idazoxan infusion. Plasma renin activity and plasma aldosterone levels decreased during volume expansion in both IDDM and control subjects. In conclusion, volume expansion induced decreased GFR in healthy controls but not in IDDM patients. Since infusion of idazoxan did not affect GFR or other parameters of renal hemodynamics, renal alpha 2-adrenoceptors do not seem to be involved in the regulation of renal function. Hence, enhanced renal alpha 2-adrenoceptor activity is not likely to underlie hyperfiltration as seen in IDDM.

Regulation of renal water excretion in newborn full-term infants

The renal response to low (45 ml/kg) and high (73 ml/kg) fluid intake was studied during an 8-hour period in healthy 3-4-day-old full-term infants. 20 infants received low fluid (LF) intake and 15 infants received high fluid (HF) intake. HF significantly increased urine flow and significantly decreased urine osmolality but did not influence glomerular filtration rate measured as the clearance of creatinine. Serum arginine vasopressin (s-AVP) was not different in the LF and HF groups and did not correlate to urine osmolality. Urinary sodium excretion was significantly correlated to the diuresis.

CONCLUSION

Following high fluid intake full-term infants are capable to adaptively excrete larger urine volumes and more dilute urine by mechanisms independent of AVP. S-AVP appears to relate differently to the state of hydration and to urine osmolality in infants than in adults.

Renal functional changes in acute glomerulonephritis in children. A one-year follow-up

Renal function was studied in three patients with post-streptococcal, four patients with IgA and one patient with non-streptococcal proliferative glomerulonephritis (GN) at the onset of the disease and two, six and 12 months later. Renal biopsies were performed at the onset of the disease and 12 months later. Standard clearance techniques were used for the functional studies. The latter were performed during hydropenia and continuous isotonic saline infusion. During hydropenia, the GFR was uniformly depressed shortly after the onset of the disease, but it normalized during the following two months. The filtration fraction was depressed in poststreptococcal GN at the onset and it normalized with the GFR. In IgA GN, the filtration fraction remained within normal limits during the entire course of the illness. The natriuretic response to isotonic saline volume expansion was low in all patients at the onset of the disease, but normalized in post-streptococcal and IgA GN during the one-year follow-up. In spite of normalized renal function, biopsy findings in IgA GN were unchanged 12 months later. An episode of macroscopic hematuria in one patient with IgA GN at the six-month investigation had no apparent effect on renal function.

Effect of vesicoureteral reflux on renal function in children with recurrent urinary tract infection.s

The functional damage caused by vesicoureteral reflux (VUR) has been examined by unilateral clearance studies in 22 children with recurrent urinary tract infection (UTI) and representing 23 kidneys with large VUR. 7 kidneys with small to moderate VUR and 14 kidneys without VUR. Inulin clearance, Na+ excretion and glucose reabsorption were determined. In kidneys without or with small and moderate VUR, UTI had no effect on renal function if treated. In kidneys with large VUR extending into the pelvis and dilating the ureter, there was a gradual deterioration of glomerular filtration rate (GFR) that was accelerated after the age of 6 yr. Before puberty more than 50% of renal function was lost despite strict medical care of the UTI. If this functional loss was unilateral, hyperfunction of the contralateral kidney was generally observed. Maximal glucose reabsorption was depressed in proportion to GFR. In kidneys with unilaterally low GFR, the fractional Na+ excretion was consistently increased as compared to the contralateral kidney with normal GFR. This adaptive increase in Na+ excretion must therefore be of intrarenal origin.

Kidney function during hydropenia nad water diuresis in patients with idiopathic recurring nephrolithiasis

The kidney function of 41 patients with idiopathic recurring kidney stones was investigated by inulin- and PAH-clearances and by measuring the excretion of electrolytes during hydropenia and water diuresis. All patients had normal inulin- and PAH-clearances and normal concentrating capacity as indicated by free water reabsorption (Tc H2O). Seven patients, all of whom had previously been found to have low excretion of magnesium in urine, were unable to dilute their urine. During water diuresis these patients also had lower osmolar clearance and lower excretion of sodium than the other patients. A defective dilution capacity may be of pathogenetic significance for stone formation; the causes of the defect, however, are not clear.