The solitary kidney: a model of chronic hyperfiltration in humans

The Effect of Higher and Lower Protein Intakes on Nitrogen Balance in Renal Transplant Recipients with Underlying Graft Dysfunction

It is essential to determine the optimum protein intake in renal transplant recipients on steroids with renal dysfunction to maintain a neutral nitrogen balance. Our aim was to study the effect of higher (1.2 g/kg/day) and lower (0.8 g/kg/day) protein intakes on nitrogen balance, body composition, glomerular filtration rate (GFR), and proteinuria in renal transplant recipients with low estimated GFR (eGFR) (15-44 mL/min/1.73 m²). This prospective, open-labeled, randomized, cross-over, interventional study enrolled patients who were ≥4 months posttransplant with eGFR between 15 and 44 mL/min/1.73 m². Subjects were randomized to either Group 1 [Diet: proteins (1.2 g/kg/day), 35 kcal/kg/day] or Group 2 [Diet: proteins (0.8 g/kg/day) and 35 kcal/kg/day] for one month. Subjects crossed over to the other diet for 2^nd month. Body composition analysis, serum creatinine, blood urea nitrogen, serum protein, serum albumin, 24-h proteinuria, GFR measurement (24 h creatinine clearance), three-day diet recall and nitrogen balance estimation were performed at baseline and at the end of the first and 2^nd month. Statistical analysis was performed using IBM SPSS Statistics version 21. Thirty-two of 35 patients completed the study. Three-day diet recall showed that daily protein and energy consumption was 1.2 g/kg and 36.47 kcal/kg with higher and 0.94 g/kg and 31.94 kcal/kg with lower protein diets, respectively. Nitrogen balance was +3.61 g/day (P = 0.0002) with higher and +1.66 g/day with lower protein diets. A significant increase was noted in muscle mass (P = 0.0317), blood urea nitrogen (P = 0.0118), GFR (P = 0.0114), and proteinuria (P = 0.010) with a higher protein diet. Renal transplant recipients remained in positive nitrogen balance with both diets. Muscle mass and proteinuria increased significantly with a higher protein diet.

Is microalbuminuria a risk factor for hypertension in children with solitary kidney?

BACKGROUND

The correlations between ambulatory blood pressure measurements (ABPM) and serum cystatin C (Cys C), serum creatinine (Cr), microalbumin (MA), and β2-microglobulin (β2-MG) levels in 24 h (24-h) urine were analyzed in children with solitary kidney (SK) and compared to healthy children.

METHODS

Fifty children with normal functioning SK and 25 controls were studied. The ABPM, serum Cys C, serum Cr, MA, and β2-MG levels in 24-h urine were measured in all children. Clinical symptoms and signs, laboratory results, urinary ultrasonography, voiding cystourethrography, and Dimercaptosuccinic acid (DMSA) scintigraphy results were recorded in the SK group. Four patients with Wilms' tumor and two with renal scarring were excluded from the study.

RESULTS

The mean ages of the SK group and controls were 9.6 ± 3.6 and 9.3 ± 3.3 years, respectively. The serum Cys C and Cr levels, 24-h urinary β2-MG and MA levels were similar in both groups (p > 0.05). However, 24-h urinary MA excretion was higher in patients living with SK more than 5 years (p = 0.01). Standard deviation scores of ABPM parameters showed no significant correlation with serum Cr, serum Cys C, MA, and β2-MG in 24-h urine of both groups.

CONCLUSIONS

Children with SK have increased 24-h urinary MA excretion in the long term, and need prolonged follow-up to detect early deterioration of renal function and to prevent end-organ damage later in life.

Renal function and solitary kidney disease: Wilms tumour survivors versus patients with unilateral renal agenesis

AIMS

To test the hypothesis that Wilms tumour survivors (WTs) experience increased disturbance in renal function, even after prompt treatment, compared to patients with unilateral renal agenesis (URA).

METHODS

To assess the renal function of 30 WTs and 17 individuals with URA, the estimated glomerular filtration rate (eGFR) was calculated using the Schwartz and Filler formulas as well as the new Schwartz equation for chronic kidney disease. To measure kidney damage, serum levels and urine excretion of β(2)-microglobulin (B2M), cystatin C (Cys C), neutrophil gelatinase-associated lipocalin (NGAL) were tested, N-acetyl-β-glucosaminidase (NAG), and albumin urine excretion and urine sediment were examined. Blood pressure was measured.

RESULTS

No differences were found between the groups in terms of eGFR, serum Cys C, B2M and NGAL concentrations. The urine excretion of Cys C, NGAL and NAG was similar in both groups. URA patients had higher B2M excretion than WTs. Arterial hypertension was present in 7/30 (23%) WTs and 1/17 (6%) patients with URA.

CONCLUSIONS

WTs have similar eGFR to individuals with URA and are more likely to have arterial hypertension. The patients with URA have signs of tubular damage. This study demonstrates the need for nephrological monitoring of individuals with a single kidney.

Cystatin C and parenchymal thickness/kidney length ratio in Wilms tumor survivors

BACKGROUND

This study presents a clinical, biochemical, and sonographic evaluation of single kidneys in Wilms tumor survivors.

PROCEDURE

The function of single kidneys in 26 Wilms tumor survivors (mean age, 11.17 years; mean follow-up, 7.09 years) was evaluated using cystatin C (CysC) levels and compared to serum creatinine concentration and glomerular filtration rate (eGFR), the latter of which was estimated by the Schwartz formula. The length of the kidney, the resistance index (RI) of the renal vessels, and the parenchymal thickness/kidney length ratio (PT/KL) were evaluated by sonographic examination.

RESULTS

Group A (n = 15) consisted of children with normal CysC levels, and group B (n = 11) consisted of children with CysC over 0.95 mg/L. No differences were observed between the groups in creatinine concentration, age, follow-up evaluation, age at the time of diagnosis, or kidney size. Children with elevated CysC had statistically lower eGFR (P = 0.02) and PT/KL (P = 0.0065). The correlation rate between CysC and PT/KL in all children was -0.38. Kidney hypertrophy was observed in 23 children and was correlated with CysC (group A, R = 0.46; group B, R = 0.4; P < 0.05). RI was normal in all individuals.

CONCLUSIONS

CysC levels may be elevated in people with normal GFR. Hypertrophy of a single kidney increases with deteriorating kidney function. PT/KL should be verified in future studies as a sonographic marker of kidney impairment.

Additive interaction between the renin-angiotensin system and lipid metabolism for cancer in type 2 diabetes

OBJECTIVE

Clinical and experimental studies suggest cross-talk between lipid metabolism and the renin-angiotensin system (RAS) in atherogenesis. The aim of this study was to explore interactions between these two systems in mediating cancer risk in type 2 diabetes.

RESEARCH DESIGN AND METHODS

A prospective cohort of 4,160 Chinese patients with type 2 diabetes, free of cancer at enrollment, were analyzed using Cox models. Interaction of RAS inhibitors (angiotensin I-converting enzyme inhibitors or angiotensin II receptor blockers) and statins was estimated using relative excess risk due to interaction (RERI), attributable proportion due to interaction (AP), and synergy index (S). RERI > 0, AP > 0, or S > 1 indicates additive interaction between the two classes of drugs. Molecular mechanisms underlying these interactions were explored using a uninephrectomy (UNX) rat model with renal carcinogenesis.

RESULTS

During 21,992 person-years of follow-up, 190 patients developed cancer. Use of RAS inhibitors and statins in isolation or combination during follow-up was associated with reduced risk of cancer after adjustment for covariates. The multivariable RERI and AP for the additive interaction between these drug classes for cancer were significant (0.53 [95% CI 0.20-0.87] and 2.65 [0.38-4.91], respectively). In the UNX rat model, inhibition of the RAS prevented renal cell carcinoma by normalizing hydroxymethylglutaryl-CoA reductase (HMGCR) expression and the insulin-like growth factor-1 (IGF-1) signaling pathway.

CONCLUSIONS

Combined use of RAS inhibitors and statins may act synergistically to reduce cancer risk, possibly via HMGCR and IGF-1 signaling pathways in high-risk conditions such as type 2 diabetes.

Urinary transforming growth factor beta1 in children and adolescents with congenital solitary kidney

The aim of the study was to assess urinary transforming growth factor beta1 (TGF beta1) level in children and adolescents with congenital solitary kidney (CSK), depending on estimated glomerular filtration rate (eGFR) and compensatory overgrowth of the kidney. The study group (I) consisted of 65 children and young adults, 0.5-22 years of age (median 10.0 years) with CSK and no other urinary defects. The control group (C) contained 44 healthy children and adolescents, 0.25-21 years old (median 10.3 years). We used an enzyme-linked immunosorbent assay (ELISA) to determine the urinary level of TGF beta1, the Jaffe method to assess creatinine concentration, and the Schwartz formula to estimate GFR. Kidney length was measured while the patient was in a supine position, and overgrowth (O%) was calculated with reference to the charts. Urinary TGF beta1 level in CSK patients was more than twice as high as that in controls (P < 0.05). Also, eGFR in patients with CSK exceeded the values in the control group (P < 0.01). Compensatory overgrowth of the solitary kidney was found (median 19.44%). Urinary TGF beta1 concentration was positively correlated with eGFR (r = 0.247, P < 0.05), uric acid concentration (r = 0.333, P < 0.01), and percentage of overgrowth (r = 0.338, P < 0.01) and body mass index (BMI) centile (r = 0.274, P < 0.05). We concluded that, although proteinuria and progressive renal insufficiency is not observed in patients with CSK during childhood, the renal haemodynamic changes are present and may be a risk factor for impairment of renal function and hypertension in future life.

Blood pressure, renal function, and proteinuria in children with unilateral renal agenesis

BACKGROUND/AIM

Unilateral renal agenesis (URA) is a model for a reduced nephron number that is believed to be a risk factor for blood pressure (BP) elevation and reduced renal function. The aim of the study was to investigate BP and renal function in children with URA.

METHODS

Data on children with URA from two pediatric nephrology centers were firstly retrospectively reviewed (renal ultrasound and scintigraphy, clinical BP, creatinine clearance, urinalysis). Children with normal renal ultrasound and scintigraphy were thereafter investigated using ambulatory BP monitoring.

RESULTS

Twenty-nine children with URA were investigated--14 children with an abnormal kidney (mostly scarring) and 15 children with healthy kidneys. Hypertension was diagnosed on the basis of clinical BP in 57% of the children with abnormal kidneys and on the basis of ambulatory BP monitoring in 1 child (7%) with healthy kidneys. The mean ambulatory BP in children with normal kidneys was not significantly different from that in controls. Forty-three percent of the children with abnormal kidneys had a reduced renal function, but none of children with normal kidneys.

CONCLUSIONS

Children with abnormalities of a solitary kidney have often hypertension, proteinuria, or a reduced renal function. In contrast, children with healthy solitary kidneys have BP and renal function similar to those of healthy children.

Assessment of serum cystatin C in children with congenital solitary kidney

The aim of the study was to assess serum cystatin C level in children with a congenital solitary kidney, depending on their age and compensatory overgrowth of the kidney. The study group (I) consisted of 36 children, 3-21 years of age (median 10.8 years), with a congenital solitary kidney and no other urinary defects. The control group (C) contained 36 healthy children, 5-21 years old (median 10.9 years). Nephelometric methods were used to determine serum cystatin C level, the Jaffe method to assess creatinine concentration and the Schwartz formula to estimate glomerular filtration rate. Kidney length was measured with the patient in a supine position, and overgrowth was estimated (O%) in comparison with the respective kidney in the control group. Serum cystatin C level in group I was higher than that in the control group (P<0.05). Increased values, above 0.95 mg/l, were found in 16/36 (44%) children aged 12-21 years. Glomerular filtration rate (GFR, estimated by the Schwartz formula) and creatinine level in group I were similar to those of the control group (P>0.05). Increased kidney length was found (median 18.2%). Cystatin C concentration was positively correlated with O% (r=0.406, P<0.01) and kidney length to child height ratio (L/H) (r=0.376, P<0.05). We conclude that Increased serum cystatin C concentration in patients with a unilateral congenital solitary kidney occurs after 12 years of age and correlates with compensatory overgrowth of the kidney.

Long-term consequences of low birth weight

There is accumulating evidence of the impact of low birth weight in adult age. Thus, the Barker theory and Brenner hypothesis gain more power. This article reviews and analyzes the evidence that supports the intrauterine origin of chronic noncommunicable diseases in adult age, particularly systemic arterial hypertension and chronic renal insufficiency. These are possibly related to lower nephron numbers, acquired in utero or later in life, which can increase susceptibility to kidney damage from diseases such as hypertension and diabetes mellitus, or cause arterial hypertension and secondary renal damage.

Impact of Graft Mass on the Clinical Outcome of Kidney Transplants

The effect of nephronic mass reduction of kidney transplants has not been analyzed specifically in a large cohort. Transplant injuries in cadaver kidney graft may have led to an underestimation of the magnitude of this factor. The aim of this study was to analyze the consequences of kidney mass reduction on transplantation outcome. The weights of 1142 kidney grafts were collected prospectively immediately before grafting. Donors and recipients <15 yr of age, simultaneous kidney/pancreas grafts, and technical failures before day 7 were excluded from the analysis. The analysis was performed on Cockroft-calculated creatinine clearance and proteinuria in 964 patients for whom all of the necessary information was available. This study reports that the smallest kidneys transplanted into the largest recipients (donor kidney weight/recipient body weight [DKW/RBW] <2 g/kg, n = 88) increased their clearance by 2.38 ml/min every month for 6 mo (P < 0.0001) and by 0.27 ml/min thereafter (P < 0.0001). Conversely, creatinine clearance did not change for the largest kidneys transplanted into the smallest recipients (DKW/RBW ratios >/=4 g/kg). Next, using a Cox model analysis, it was shown that the risk of having a proteinuria >0.5 g/kg was significantly increased for the low DKW/RBW ratios <2 g/kg with 50% of patients having a proteinuria, compared with DKW/RBW ratios >/=4 g/kg (P < 0.001). In cadaver transplant recipients, graft mass has a rapid impact on graft filtration rate and proteinuria. Avoiding major kidney/recipient inadequacy should have a significant influence on long-term transplant function.

Long-term protein intake control in kidney transplant recipients: effect in kidney graft function and in nutritional status

BACKGROUND

Reduction in renal mass is followed by progressive renal failure. The reduction in filtration surface area, caused by the absence of 50% of renal mass, in patients with customary salt intake is followed by expansion of extracellulary volume and systemic and glomerular hypertension. High protein intake may contribute to renal allograft injury arising from insufficient renal mass.

METHODS

The authors studied outcome of 48 patients with kidney transplant to whom normocaloric diets and moderate intake of protein (0.8 g/kg), of sodium (3 g/d), and lipids (no more than 30% of total energy) were prescribed. Monthly 24-hour urea excretion and 24-hour sodium excretion were measured. Renal function was assessed by creatinine clearances and by renal scintigraphy. The 30 patients who followed prescriptions exactly were the compliant group (group 1). The other 18, who followed the diet prescribed only partially (their intakes were 1.4 g/kg of protein and 5 g/d of sodium) were the control group (group 2).

RESULTS

Patients of the compliant group maintained unchanged renal function, whereas patients of the control group lost more than 40% of excretion efficiency as a mean.

CONCLUSIONS

Dietary restrictions of protein and sodium can stabilize renal function in patients with kidney transplant. Wider use of this treatment is indicated.

Measurement of renal vein blood flow in rats by high-field magnetic resonance

The aim of the present study was to examine whether magnetic resonance imaging (MRI) based method for non-invasive in vivo measurement of vein blood flow in rats could be used to estimate renal blood flow (RBF). Measurements were performed using a high-field (7 Tesla) MRI scanner with a short echo time phase contrast velocity measurement pulse sequence. The method was evaluated in vitro by flow measurements in an acrylic pipe and in vivo by recording left renal vein blood flow in normal and unilaterally nephrectomized rats. In a subset of animals RBF was measured by a direct method using 14C-tetraethylammoniumbromide. In vitro a high accuracy was found between applied and MRI measured flow rates in the range from 0.5 to 33 ml/min (r = 0.997; P < 0.001). In vivo the MRI measured left renal vein blood flow was 70% higher in unilaterally nephrectomized animals compared to control animals (3.4 +/- 0.4 ml/min/ 100 g body wt vs. 2.0 +/- 0.1 ml/min/100 g body wt, P < 0.001). Direct measurements of RBF revealed comparable values (3.4 +/- 0.3 ml/min/100 g body wt vs. 2.3 +/- 0.4 ml/min/100 g body wt, P = 0.05). In addition, the left kidney volume was recorded by MRI with an increase amounting to 40% (1.18 +/- 0.05 ml vs. 0.84 +/- 0.02 ml; P < 0.001) in the nephrectomized group compared to controls. Finally, a positive correlation was seen between left renal vein blood flow and MRI measured renal volume (r = 0.91; P < 0.001). In summary, MRI is a non-invasive tool by which measurement of renal vein blood flow can be performed, and it is concluded that MRI-based renal vein flow measurements can be used to estimate RBF in small rodents.

Image-directed color Doppler ultrasound evaluation of the single kidney after unilateral nephrectomy in adults

Renal adaptations occur in the single kidney. The kidney of 21 unilaterally nephrectomized adults was studied with image-directed color Doppler ultrasound (ICDU) and compared with 35 age-matched controls. Kidney volume, standardized kidney volume, hypertrophy, both intrarenal- and main renal artery-resistive indexes were quantified, correlated to each other and correlated to renal function. The influence of age, sex, or time since nephrectomy was also studied. There was a mean hypertrophy of approximately 20%. Intrarenal resistances lay within normal limits for age. There was no correlation between renal function, size, and hemodynamics. Age, sex, and time since nephrectomy had a limited influence on renal adaptations.

Renal function after unilateral nephrectomy for Wilms' tumour: the influence of radiation therapy

The effect of therapy on renal function after unilateral nephrectomy for Wilms' tumour was studied. In the second year following unilateral nephrectomy, glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were estimated simultaneously by measuring 125I-iothalamate clearance and 131I-hippurate clearance. Of 41 evaluable patients, 29 received chemotherapy as sole treatment modality following nephrectomy (group 1); 12 patients additionally received radiation therapy to a field that included the remaining kidney (group 2). Results were expressed as standard deviation scores (z-scores). In group 1, mean z-score for GFR was -0.27 (94.6% of normal) and in group 2 mean z-score was -1.51 (72.7% of normal for two kidneys) (P = 0.022, Mann-Whitney U-test). Mean z-score for ERPF was -0.09 (97.0%) in group 1 and -1.53 (73.8%) in group 2 (P = 0.039). It was concluded that the combination of chemotherapy and radiation therapy, in contrast to chemotherapy alone, negatively affects the ability of the remaining kidney to adjust its function after the loss of its counterpart.

Status of patients who underwent uninephrectomy in adulthood more than 20 years ago

We investigated the status of patients without systemic diseases who had undergone uninephrectomy for unilateral renal diseases in adulthood more than 20 years ago at Tokyo Denryoku Hospital. There were 21 participants (mean age +/- SD, 58.6 +/- 8.0 years) who fulfilled these criteria. The average interval since nephrectomy was 27.9 +/- 6.2 years. The mean current creatinine clearance was 88.5 +/- 21.2 mL/min/1.73 m2, which is 92.9% of that in healthy age- and sex-matched controls with two kidneys. The 24-hour urine protein excretion in these patients was only slightly higher than in the controls (214 +/- 190 mg v 119 +/- 62 mg, P = NS). Age at nephrectomy, length of time with a single kidney, or sex had little effect on the remnant renal functions. There was a positive correlation between current mean arterial pressure and serum creatinine (r = 0.44, P < 0.05). Patients who developed hypertension after uninephrectomy had a family history of hypertension more frequently than those with normotension (86% v 29%, P < 0.05). We conclude that (1) renal function after compensatory hyperfiltration of more than 20 years due to uninephrectomy for unilateral renal diseases in adulthood is well maintained, although hypertension has a considerable effect on the renal functions, and that (2) family history of hypertension plays a key role in determining the incidence of hypertension even in the uninephrectomized patients.

Renal function following unilateral nephrectomy for neuroblastoma and Wilms' tumour

To estimate the side effects of chemotherapy and the influence of age at the time of nephrectomy on renal function, we investigated renal function in 34 uninephrectomised children with neuroblastoma (NB) or Wilms' tumour (WT). The results were compared with 6 controls who underwent nephrectomy for non-malignant disease. Study of renal function was primarily based on the clearance of inulin and para-aminohippuric acid (Cin and CPAH, ml/min per 1.73 m2). No significant differences in Cin/CPAH (mean +/- SD) were found between the NB group (90 +/- 24/421 +/- 95), WT group (85 +/- 17/386 +/- 104) and the controls (93 +/- 13/430 +/- 61). Children with NB and WT were divided into two subgroups according to the theoretical nephrotoxic risk. There was no significant difference in renal function between NB or between WT subgroups. Cumulative cisplatin doses in children with NB did not affect renal function significantly. The age at time of unilateral nephrectomy (< or = 2 years vs. > 2 years) was not associated with a higher risk of renal damage in WT children, whereas in NB children the filtration fraction (Cin:CPAH) was higher in younger children (mean +/- SD: 0.243 +/- 0.023 vs. 0.191 +/- 0.041). In conclusion, uninephrectomised children with NB are supposed to have a higher risk of drug-induced renal impairment compared with those with WT. Our data do not confirm this hypothesis, since renal function was comparable to controls in both groups, except in younger patients with NB who show a high filtration fraction. Since the survival of children with NB has improved, a longer follow-up of their renal function in needed.

A quantitative analysis of the glomeruli in focal segmental glomerulosclerosis

Quantitative analysis of the glomerular area, mesangial matrix and mesangial cells was performed using renal biopsy specimens from 22 children with focal segmental glomerulosclerosis (FSGS) and 20 with minimal change nephrotic syndrome (MCNS). Non-sclerotic glomeruli were examined. All children in both groups showed nephrotic syndrome at the time of biopsy. Children with benign haematuria were examined as controls. Glomerular area increased with age in the FSGS, MCNS and control groups. The glomerular area was significantly greater in FSGS (1.5 +/- 0.4 x 10(4) microns 2) than in MCNS (1.2 +/- 0.2 x 10(4) microns 2) or in controls (1.2 +/- 0.3 x 10(4) microns 2) (P < 0.05). Mesangial matrix was increased with age in the three groups. The mesangial matrix was significantly increased in FSGS (28.3 +/- 4.0%; mesangial matrix area/glomerular area) compared with MCNS (24.9 +/- 4.1%) and controls (23.0 +/- 3.0%) (P < 0.01). These findings suggest that both glomerular hypertrophy and mesangial matrix increase in non-sclerotic glomeruli in FSGS may lead to glomerular sclerosis.

Renal functional reserve in cyclosporin-treated recipients of kidney transplant

The aims of this study were to determine whether renal functional reserve (RFR) is still present in cyclosporin-treated renal transplant recipients, and to examine the relationship between RFR and proximal reabsorption. A serial study was carried out in 12 renal allograft recipients (R) with good renal graft function at 20 +/- 2.5 days (S1) and at 7.6 +/- 0.4 months (S2) post-transplantation, and the results were compared to those in eight subjects who had undergone unine-phrectomy (one-kidney controls: UNx.C) and in 12 healthy volunteers (two-kidney controls: 2K.C). R and C were in similar sodium and protein balance and with similar plasma renin and aldosterone levels. R had normal serum creatinine level on moderate doses of cyclosporin (whole blood cyclosporin concentration: 212 +/- 20 and 125 +/- 20 ng/ml at S1 and S2, respectively). Eight one-hour clearance periods were performed prior to, during and following a three-hour i.v. infusion of a mixture of 20 l-amino acids (Azonutril 25, 4.5 mg amino acids/kg/min). Baseline glomerular filtration rate (GFR) was lower in recipients at S1 and S2 (55 +/- 5 and 54 +/- 4 ml/min/1.73 m2, respectively) than in UNx.C and 2K.C (72 +/- 4 and 113 +/- 4 ml/min/1.73 m2, respectively, P < 0.05 and 0.001). Amino acid infusion elicited significant GFR increases in controls as well as in recipients in spite of higher renal vascular resistances (RVR). The greater measured increase in GFR, which represented RFR, was 18 +/- 3 and 28 +/- 2 ml/min/1.73 m2 in UNx.C and 2K.C, respectively (P < 0.001), and 17 +/- 3 ml/min/1.73 m2 in R at both S1 and S2 (P < 0.001). Contrary to both UNx and 2K controls, the acute hyperfiltration in R at S1 and S2 occurred with a significant increase in effective renal plasma flow, no alteration in filtration fraction and a large decrease (approximately 20 and 17%) in RVR while no correlation could be detected between the RFR and baseline GFR. Baseline lithium clearance, used as a marker of overall proximal fluid delivery (CLi), was significantly lower, whereas baseline fractional excretion of lithium (FELi) was significantly higher in R at S1 and S2 and in UNx.C (41 +/- 4, 40 +/- 3 and 38 +/- 3%, respectively) than in 2K.C (31 +/- 2%, P < 0.05). Consistent and significant increase in CLi, FELi and absolute proximal reabsorption occurred both in R at S1 and S2 and in UNx and 2K controls during elicitation of RFR.(ABSTRACT TRUNCATED AT 400 WORDS)

Hemodynamic theory of progressive renal disease: a 10-year update in brief review

Experimental studies have suggested that glomerular hypertension is ultimately damaging to the kidney. Prevention of glomerular hypertension by dietary protein restriction or antihypertensive therapy lessens glomerular injury in several experimental models of chronic renal disease. Glomerular hypertension and hyperfiltration also occur in humans with diabetes mellitus, solitary or remnant kidneys, and various forms of acquired renal disease. Clinical studies are beginning to show that dietary protein restriction and antihypertensive therapy may slow progression in these disorders. Large multicenter trials are currently under way to better define the effects of these therapeutic maneuvers on the progression of chronic renal disease.

Renal function up to 50 years after unilateral nephrectomy in childhood

Removal of one kidney during childhood differs from removal of a kidney from an adult as the child's future depends on an adequate function of the remaining kidney during a longer period of time. We assessed the long-term effect of unilateral nephrectomy in childhood on renal function, protein excretion, and blood pressure. Data were obtained from 111 subjects undergoing uninephrectomy for unilateral renal disease before the age of 16 years who had no evidence of renal abnormalities in the contralateral kidney at the time of surgery. At investigation the patients were 18 to 56 years of age with an interval of up to 52 years after uninephrectomy. On average, renal function was well maintained at approximately 75% of the reported normal two-kidney value. Blood pressure in men was higher than in women. Stratification for age showed no statistically significant differences between those undergoing uninephrectomy before or after the age of 4.5 years. Stratification for post-uninephrectomy interval revealed renal function to be lower and blood pressure, urinary albumin excretion, and protein excretion to be higher in those with an interval of more than 25 years. In men over 30 years of age, linear regression analysis indicated a decrease in glomerular filtration rate, effective renal plasma flow, and creatinine clearance, and an increase in blood pressure and albumin excretion with time. Controlled longitudinal studies are needed to detect true changes and to ascertain whether such changes are different from the age-related changes seen in individuals with two kidneys.(ABSTRACT TRUNCATED AT 250 WORDS)

Nephron underdosing: a programmed cause of chronic renal allograft failure

The findings cited in this report suggest that renal allograft survival might be improved by matching nephron supply to recipient needs (analogous to prescription dialysis based on Kt/V). Methods for assessing functional graft capacity (ie, nephron number, filtration, or total microvascular surface area) are needed. Graft weights might serve as a useful alternative until better indices are devised. Measures for defining and possibly reducing recipient demands are also needed to preserve graft performance. Where gross imbalances between nephron supply and recipient demand are not likely to be corrected over the long term by engraftment of a single kidney, consideration should be given to dual kidney transplantation, currently feasible only from cadaveric, but eventually from xenogeneic sources as well. The predicted longer survival and avoidance of premature return to end-stage renal disease with the transplantation of two kidneys in certain conditions could render this approach more rational, both in clinical and economic terms, than single kidney engraftment for those at greatest risk for shortened graft survival. The dosing of larger numbers of nephrons might also lessen the risk of coexistent hypertension and thereby reduce the magnitude and tempo of immune injury to the graft.

Unilateral nephrectomy and progression of renal failure

Extensive ablation of renal mass in experimental animals leads to progressive glomerulosclerosis and chronic renal failure (CRF). Clinical studies are far from answering the question whether patients with reduced renal mass are at risk of developing progressive CRF. The aim of our study was to examine the morphological and functional aspects of the remnant kidney in a group of patients who underwent unilateral nephrectomy for renal tuberculosis: 313 patients (161 M, 152 F) mean age 57.2 +/- 10.7, were examined after a period ranging from 13.56 to 591.2 months. All patients were on ad libitum diet. Hypertension was found in 34.19% of the patients; SBP was 155.29 +/- 19.9 mmHg and DBP was 92.74 +/- 13.07 mmHg. Estimation of renal size performed by ultrasound scanner gave the following results: length 116.78 +/- 8.99 mm; width 58.24 +/- 7.21 mm; thickness 17.88 +/- 1.96 mm. Kidney function assessed by serum creatinine levels showed a mean level of 1.28 +/- 0.53 mg%. Forty-two patients (13.41%) had serum levels > 1.5 mg% but 18 of them had nonconcomitant systemic or renal involvement. Microalbuminuria determined by RIA assay was found in 50.5% of the patients. In our group of patients renal functional impairment was low and hyperfiltration expressed as microalbuminuria does not appear to be a primary factor in the progression of renal failure.

Evidence for activation of tubuloglomerular feedback following nephrectomy in human subjects

The intrarenal regulation of glomerular filtration rate (GFR) following a reduction in renal mass was evaluated in six normal subjects, studied before and 4 to 6 weeks after undergoing unilateral nephrectomy, performed for the purpose of living-related transplantation. The role of the tubuloglomerular feedback (TGF) system in regulating the final GFR on both occasions was assessed by determining the increase in GFR over baseline levels following blockade of TGF by a single dose of bumetanide, care being taken to replace sodium and water losses. Before donor nephrectomy, baseline GFR was 115 +/- 7 mL/min, which increased by 9.5% +/- 2.5% to 126 +/- 9 mL/min following the removal of TGF. Four to six weeks following donor nephrectomy, the baseline GFR was 83 +/- 8 mL/min, confirming significant hyperfiltration in the remaining kidney. After administration of bumetanide, the GFR increased by 15.6% +/- 3.1% to 96 +/- 9 mL/min. This greater fractional increase (P < 0.025) indicates an increase in tonic TGF activity in the uninephrectomized state compared with that demonstrated before nephrectomy. The results suggest that the hyperfiltration response following unilateral nephrectomy is limited by an appropriately activated TGF system. This phenomenon may be of importance in the maintenance of Na and water homeostasis, as well as limiting the pathological consequences that may result from, or be exacerbated by, an excessively high filtration rate in the remaining nephrons. Thus, dietary or therapeutic maneuvers that impair the TGF response may be best avoided following a reduction in renal mass.

Factors affecting renal allograft function in long-term recipients

The natural history of renal allograft function in long-term recipients is not known. To characterize renal allograft function and the factors that affect it, we reviewed the records of all patients who received a renal allograft at the University of Wisconsin between 1965 and 1981 and selected those who had annual data on renal function for at least 10 years. We identified 155 patients--78 with living-related donors and 77 with cadaveric donors. All patients were adults receiving azathioprine and prednisone. Renal function was estimated by calculated creatinine clearances (Ccr), which correlated well with measured 24-hour creatinine clearances. The creatinine clearance data for each patient were plotted versus time. In 73% of patients, the creatinine clearance increased for several years before reaching a peak value. After the peak, the creatinine clearance declined in a linear manner. Stepwise regression analyses indicated that allografts from cadaveric donors had a greater increase in creatinine clearance from the value at year 1 to the peak than allografts from living-related donors (0.35 +/- 0.25 v 0.21 +/- 0.23 mL/s [21.4 +/- 15.0 v 12.7 +/- 13.8 mL/min]; P less than 0.001). The average time to reach the peak value of creatinine clearance was longer in cadaveric allografts (6.8 +/- 3.5 v 4.6 +/- 4.0 years; P less than 0.001). Postpeak, the rate of decline in creatinine clearance was faster in cadaveric allografts than in living-related ones (0.06 +/- 0.05 v 0.04 +/- 0.04 mL/s/yr [3.50 +/- 2.99 v 2.55 +/- 2.16 mL/min/yr]; P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term follow-up of a human subject with a remnant kidney

It has been proposed that once functioning renal mass has been reduced below a critical level, either as the result of disease, congenital absence of a kidney, or surgical ablation, that hyperfiltration and glomerular hypertension lead to progressive glomerular sclerosis and end-stage renal failure. We report the clinical course and renal function of a human subject followed for 10.8 years after extensive renal ablation. Functioning renal mass was estimated at one fourth to one fifth of normal. During the follow-up period, creatinine clearance increased from 0.27 mL/s (16 mL/min) to 0.88 mL/s (53 mL/min), the total renal plasma flow (all of which was to the left kidney) increased from 62 mL/min to 190 mL/min, and 24-hour urine protein excretion increased from 0.09 g to 0.4 g. Despite probable glomerular hyperfiltration, neither progressive glomerular dysfunction nor end-stage renal failure developed over a period of 10 years.

Do glomerular hemodynamic adaptations influence the progression of human renal disease?

Although experiments in the rat suggest that glomerular hemodynamic alterations following a reduction of renal mass may be implicated in the progression of chronic renal failure, we argue that the deleterious effects of similar adaptations in human renal disease are unproven. In the otherwise normal solitary kidney the supranormal glomerular filtration rate (GFR) remains stable over the longterm, and in early diabetic nephropathy which is also accompanied by hyperfiltration, renal deterioration cannot be dissociated from a rise in systemic blood pressure. In patients with miscellaneous renal diseases and a depressed basal GFR there is indirect evidence that hyperfiltration might occur in some of the remnant glomeruli. However, at present there is little conclusive evidence to indicate that therapies which might normalize glomerular hemodynamics, e.g., dietary protein restriction, have any effect on progression of renal disease, or that angiotensin converting-enzyme inhibitors, which lower glomerular capillary pressure, have any advantage over other antihypertensive agents which are equally efficacious in lowering systemic blood pressure.

Morphological findings in 70 kidneys of living donors for renal transplant

Seventy donor kidneys for transplant were studied with light microscopy (LM), electron microscopy (EM) and immunofluorescence (IM) for C3, C4, Clq, IgG, IgA, IgE, IgM, and antifibrin; the samples were taken just before transplanting the allograft kidney. Glomerular changes were found in 35.7% of apparently normal living donors: 9 cases showed relative glomerular ischemia with an irregular basal membrane (12.9%); 5 cases showed a diffusely widened basal membrane without antecedents of hyperglycemia (7.1%); in one case (1.4%) there was a lesion similar to type 1 mesangio-capillary glomerulonephritis with C3++, IgG++, IgA+, and IgM+; in another case (1.4%) there were scant isolated C3 glomerular, subepithelial deposits with indentation of the basement membrane of the immunocomplex type with a microhematuria which was demonstrated only after donation, and in 9 cases (among them two pairs of siblings) there were mesangial IgA and mesangial electron-dense deposits compatible with Berger's disease (12.9%). None of these glomerulopathies were evident under LM.

Glomerular hypertrophy in minimal change disease predicts subsequent progression to focal glomerular sclerosis

The study sought a diagnostic clue to identify the group of pediatric patients with apparent minimal change disease who subsequently develop focal glomerular sclerosis (FGS). Review of all renal biopsy material at our institutions identified 42 pediatric patients who met the standard criteria for minimal change disease (MCD) on initial biopsies. Of those, 10 deteriorated clinically and on rebiopsy showed focal glomerular sclerosis (FGS). The initial renal biopsies of these 10 patients were analyzed morphometrically to determine the mean glomerular tuft area (GA). The results were compared to those of the remaining 32 patients whose subsequent benign clinical course was consistent with MCD, and to randomly selected, age-matched autopsy controls without renal disease (CONT, N = 10). The mean age was comparable among the three groups studied. Separate groups of adult (N = 12) and pediatric (N = 18) patients with initial biopsies with FGS were also studied. The initial biopsy of pediatric patients who subsequently showed FGS (rebiopsy performed on average 3.3 years later) had an average GA of 13.5 x 10(-3) mm2, 76% larger than glomeruli from children with MCD (7.7 x 10(-3) mm2, P less than 0.0005) and 62% larger than CONT (8.4 x 10(-3) mm2, P less than 0.005). Patients with FGS on initial biopsy, whether adult or pediatric, also had significantly larger GA than the age-matched MCD or CONT groups. Evaluation of GA in all the 42 pediatric biopsies with initial MCD further showed that in 23 patients GA was equal to or smaller than the CONT average.(ABSTRACT TRUNCATED AT 250 WORDS)