Renal growth and function in patients nephrectomized in childhood

Increased risk for kidney sequelae surrogates in survivors of Wilms tumor

BACKGROUND

There is evidence of increased risk of hypertension, albuminuria, and development of chronic kidney disease (CKD) in long-term follow-up of survivors of Wilms tumor (WT). However, most studies were conducted in heterogeneous groups, including patients with solitary kidney. In addition, little is known about tubular dysfunction. This study aimed to investigate kidney sequelae, including CKD development, hypertension, and glomerular and tubular damage in WT survivors.

METHODS

This cross-sectional, single-center study included 61 patients treated for WT. Surrogates for kidney sequelae were defined as presence of at least one of the following: decrease in GFR for CKD, hypertension detected by ambulatory blood pressure monitoring, albuminuria (albumin-to-creatinine ratio [ACR] > 30 mg/g), or increase in at least one tubular biomarker (beta-2-microglobulin, neutrophil gelatinase-associated lipocalin, kidney injury marker-1, and liver fatty acid-binding protein) in 24-h urine.

RESULTS

Median age of patients was 11.7 years, with median follow-up of 8.8 years. Thirty-eight patients (62%) had at least one surrogate for kidney sequelae. Twenty-four patients (39%) had CKD, 14 patients (23%) had albuminuria, 12 patients (21%) had hypertension, and 11 patients (18%) had tubular damage. Urine ACR was significantly higher in patients with advanced tumor stage and patients with nephrotoxic therapy than their counterparts (p < 0.05), but neither eGFR nor tubular biomarkers showed any association with tumor- or treatment-related factors.

CONCLUSIONS

A considerable number of patients with WT have kidney sequelae, especially early-stage CKD with a high prevalence. Albuminuria emerges as a marker associated with tumor stages and nephrotoxic treatment. A higher resolution version of the Graphical abstract is available as Supplementary information.

Kidney injury rates after unilateral nephrectomy in childhood-a systematic review and meta-analysis

BACKGROUND

Unilateral nephrectomy is a relatively common procedure in children which results in a solitary functioning kidney (SFK). Living with an SFK predisposes to kidney injury, but it remains unknown which children are most at risk. We aimed to investigate kidney injury rates in patients who underwent unilateral nephrectomy in childhood and to investigate differences among nephrectomies performed for a congenital anomaly, malignancy or other condition.

METHODS

MEDLINE and EMBASE were searched for studies reporting kidney injury rates [i.e. proteinuria, hypertension and/or a decreased glomerular filtration rate (GFR)] of patients who underwent unilateral nephrectomy during childhood. Studies including five or more patients with at least 12 months of follow-up were eligible. Analyses were performed using random effects models and stratified by indication for nephrectomy. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and Meta-analysis Of Observational Studies in Epidemiology (MOOSE) guidelines were used for reporting.

RESULTS

Over 5000 unique articles were screened, of which 53 studies reporting on >4000 patients were included in the analyses. Proteinuria, hypertension and a decreased GFR were present in 15.3, 14.5 and 11.9% of patients, respectively. Heterogeneity among the studies was large in several subgroups, impairing quantitative meta-analyses. However, none of our analyses indicated differences in injury rates between a congenital anomaly or malignancy as an indication for nephrectomy.

CONCLUSIONS

Unilateral nephrectomy during childhood results in signs of kidney injury in >10% of patients, with no clear difference between the indications for nephrectomy. Therefore, structured follow-up is necessary in all children who underwent nephrectomy, regardless of the indication.

Influence of Vesicoureteral Reflux and Urinary Tract Infection on Renal Growth in Children with Upper Urinary Tract Duplication

The growth of the renal parenchyma was examined in children with duplicated outflow systems, vesicoureteral reflux (VUR), urinary tract infection (UTI) and no sign of obstruction. Ten patients with reflux occurring only in the caudal system (group A) and 4 patients with reflux both to the caudal and the apical system (group B) were studied shortly after their first UTI (study 1) and then 1.5 to 9 years later (study 2). The frequency of UTI was relatively high during the follow-up period. At urography, renal length and renal area were normal in group A in studies 1 and 2. Parenchymal thickness of the apical pole (APT/L) did not differ from normal values in any of the studies. Parenchymal thickness of the caudal pole (CPT/L) was significantly smaller than normal in both studies. There was also a significant decrease in CPT/L between study 1 and 2. UTI during the first year of life was associated with a greater reduction in CPT/L. The determination of renal length and renal area in children with a duplicated ureter, VUR and UTI, does not identify subjects at risk of developing renal growth retardation while serial determinations of parenchymal thickness appear to be an appropriate method.

Impact of nephrectomy on long-term renal function in non-syndromic children treated for unifocal Wilms tumor

OBJECTIVE

The present study is designed to assess the long-term renal function of children who underwent radical nephrectomy for unifocal Wilms tumor.

METHODS

A single institution retrospective cohort study of non-syndromic children treated with radical nephrectomy for unifocal Wilms tumor between 1995 and 2011 was performed to identify risk factors for decreased glomerular filtration rate (GFR). The primary endpoint was decrease in age-adjusted GFR below normal published ranges. The secondary endpoint was progression to chronic renal insufficiency (CRI).

RESULTS

A total of 55 patients were identified in the cohort. Eight (15%) patients exhibited decreased age-adjusted GFR during the follow-up period, with 2 (4%) progressing to CRI. Increasing time between surgery and the last known GFR follow-up was associated with decreased GFR, with the normal GFR group having median follow-up of 7.32 years versus 11.47 years (p = 0.019) in the decreased GFR group.

CONCLUSIONS

A trend toward decline in GFR was detected with longer follow-up. Longer follow-up may reveal that clinically significant decline in renal function occurs years following nephrectomy among a subset of Wilms tumor survivors, even among those who do not progress to end stage renal disease.

The late effects of anticancer therapy after childhood Wilm's tumor: the role of diastolic function and ambulatory blood pressure monitoring

OBJECTIVE

Wilms' tumor, or nephroblastoma, is the most common primary malignant renal tumor of childhood. The excellent outcome now expected for most children with this tumor is attributed to the combination of effective adjuvant chemotherapy, improved surgical and anesthetic techniques and also the radiosensitivity of the tumor. The numerous organ systems are subject to the late effects of anticancer therapy. The aim of this study was to investigate the blood pressure profile and ambulatory blood pressure monitoring, and also cardiac diastolic functions and pulmonary venous flow in 25 children with unilateral Wilms' tumor in remission.

METHODS

The patient group consists of 25 patients who successfully completed anticancer treatment for unilateral Wilms' tumor. Thirty-three age-, weight- and height-matched healthy children were considered as a control group for an echocardiographic study. Also, 20 age-, weight- and height-matched healthy children were considered as a control group for the ambulatory blood pressure monitoring study.

RESULTS

In our study, 24 h, daytime and night-time systolic blood pressure and night-time diastolic blood pressure measurements were found to be significantly increased in the patient group compared with healthy children. We detected diastolic filling pattern abnormalities. We also found increase in pulmonary venous flow (systolic and diastolic) in Wilms' tumor group.

CONCLUSIONS

We suggest the regular follow-up of survivors of Wilms' tumor for care and prevention of cardiovascular diseases.

Renal programming: cause for concern?

Development of the kidney can be altered in utero in response to a suboptimal environment. The intrarenal factors that have been most well characterized as being sensitive to programming events are kidney mass/nephron endowment, the renin-angiotensin system, tubular sodium handling, and the renal sympathetic nerves. Newborns that have been subjected to an adverse intrauterine environment may thus begin life at a distinct disadvantage, in terms of renal function, at a time when the kidney must take over the primary role for extracellular fluid homeostasis from the placenta. A poor beginning, causing renal programming, has been linked to increased risk of hypertension and renal disease in adulthood. However, although a cause for concern, increasingly, evidence demonstrates that renal programming is not a fait accompli in terms of future cardiovascular and renal disease. A greater understanding of postnatal renal maturation and the impact of secondary factors (genes, sex, diet, stress, and disease) on this process is required to predict which babies are at risk of increased cardiovascular and renal disease as adults and to be able to devise preventative measures.

Consequences of Intrauterine Growth Restriction for the Kidney

Low birth weight due to intrauterine growth restriction is associated with various diseases in adulthood, such as hypertension, cardiovascular disease, insulin resistance and end-stage renal disease. The purpose of this review is to describe the effects of intrauterine growth restriction on the kidney. Nephrogenesis requires a fine balance of many factors that can be disturbed by intrauterine growth restriction, leading to a low nephron endowment. The compensatory hyperfiltration in the remaining nephrons results in glomerular and systemic hypertension. Hyperfiltration is attributed to several factors, including the renin-angiotensin system (RAS), insulin-like growth factor (IGF-I) and nitric oxide. Data from human and animal studies are presented, and suggest a faltering IGF-I and an inhibited RAS in intrauterine growth restriction. Hyperfiltration makes the kidney more vulnerable during additional kidney disease, and is associated with glomerular damage and kidney failure in the long run. Animal studies have provided a possible therapy with blockage of the RAS at an early stage in order to prevent the compensatory glomerular hyperfiltration, but this is far from being applicable to humans. Research is needed to further unravel the effect of intrauterine growth restriction on the kidney.

Compensatory renal growth due to neonatal ureteral obstruction: implications for clinical studies

In response to unilateral ureteral obstruction (UUO), the contralateral kidney undergoes compensatory renal growth, which is enhanced in early development. We investigated the renal growth response to UUO in the neonatal rat. Within 2 days of birth, animals were subjected to sham-operation, complete UUO, or variable partial UUO, and kidneys were harvested 3-60 days later. Contralateral kidney weight increased after only 7 days of complete UUO. Increase in contralateral kidney weight was not significant for partial UUO until 45 days, but kidney/body weight ratio increased after only 14 days of 0.3 mm partial UUO. The rate of contralateral renal growth increased with age and with increasing severity of UUO. In rats subjected to 45 days UUO, glomerular area was proportional to kidney/body weight ratio (r =0.61, p <0.01). We conclude that the rate of compensatory renal growth is dependent on the severity and duration of obstruction, and takes place at the single nephron level. The results suggest that biologic variability limits the early detection of compensatory renal growth, which is compounded by limitations in measuring renal size by clinical imaging. Factoring kidney length (or volume) by intervertebral length (or body surface area) should improve the precision of tracking renal growth.

Follow-up after unilateral nephrectomy in children: is an estimate of glomerular filtration rate necessary?

OBJECTIVE

To determine the need for an estimate of glomerular filtration rate (GFR) in the follow-up of children undergoing unilateral nephrectomy for benign renal disease.

PATIENTS AND METHODS

Forty-four children (21 girls and 23 boys) undergoing unilateral nephrectomy for benign renal disease over a 3-year period were reviewed for the underlying diagnosis and indication for nephrectomy, imaging before and after surgery, postoperative GFR and final outcome. The follow-up included ultrasonography (US) of the contralateral kidney at 3 and 12 months and an estimate of GFR before discharge at > or = 1 year. All children were aged > 2 years when the GFR was measured. The criteria for discharge were normal imaging of the contralateral kidney before and after surgery and a normal GFR afterward. Spearman's correlation coefficient was used to determine the relationship between age, GFR and contralateral renal length after surgery.

RESULTS

The median (range) age at surgery was 2.5 (0.67-16) years. The indications for nephrectomy included reflux nephropathy in 18, multicystic dysplastic kidney in 12, a congenital obstructive uropathy in eight, congenital renal dysplasia in four and miscellaneous in two. All patients had a normal contralateral kidney before surgery on US and functional imaging, and normal US at the follow-up, with evidence of compensatory hypertrophy in all. The median (range) corrected GFR for the 44 children was 109 (81-140) mL/min/1.73 m2, with no correlation between age and GFR, or between renal length and GFR.

CONCLUSION

After unilateral nephrectomy for benign renal disease, provided there is a structurally and functionally normal contralateral kidney before surgery, with no abnormality on US, a routine estimate of GFR is unnecessary before discharge from follow-up. There was no correlation between GFR and age or renal length.

Management of neonatal ureteropelvic junction obstruction

No topic in urology is more contentious than the management of neonatal ureteropelvic junction obstruction. Those favoring early diagnosis and correction of obstruction in early infancy cite excellent return of function and superior surgical results compared with delayed repair. Others believe that hydronephrosis improves or resolves with growth in many instances. In the most widely quoted series, almost all such patients improved. This article attempts to separate opinion from fact. The arguments for early surgery and for observation, even when obstruction has been diagnosed, are reviewed. Several experiences with long-term surveillance are summarized.

Renal growth in children with severe vesicoureteral reflux: 10-year prospective study of medical and surgical treatment: the International Reflux Study in Children (European branch)

PURPOSE

To determine whether medical or surgical treatment better promotes renal growth in children with severe vesicoureteric reflux (VUR) and to examine factors influencing renal growth.

MATERIALS AND METHODS

Three hundred two children younger than 11 years with urinary tract infection and grade III or IV VUR were randomly assigned to surgical (n = 149) or medical (n = 153) treatment and were followed up at serial intravenous urography for up to 5 years; 223, for up to 10 years (surgical, n = 110; medical, n = 113). Renal size was measured planimetrically on serial intravenous urograms and was related to the virtual height of L1 through L3 by expressing it as an SD score.

RESULTS

There was no significant difference in mean renal growth between patients treated surgically or those treated medically after 5- or 10-year follow-up. Bilateral renal size of 80 surgical and 75 medical patients remained within 1 SD score. In patients entering the study at 2 years of age or younger and in those with grade IV VUR, bilateral VUR, or renal scars, there was a trend toward improved renal growth in those treated medically, but this finding was not statistically significant. When renal scarring or thin parenchyma was unilateral, the affected kidney grew less well, irrespective of treatment. Bilateral renal scarring was usually asymmetrical, with a corresponding effect on renal growth.

CONCLUSION

There was no significant difference in renal growth during 10 years between surgical and medical treatment in patients with severe reflux.

The effect of Wilms tumor chemotherapy on contralateral renal growth after nephrectomy

PURPOSE

Our aim was to evaluate the effect of current Wilms tumor chemotherapy on renal growth and function after unilateral nephrectomy.

MATERIALS AND METHODS

Yorkshire piglets were enrolled in 2 study groups: group 1--6 underwent unilateral nephrectomy and placebo infusion, and group 2--10 underwent nephrectomy, and infusion of 7.5 mcg/kg. actinomycin D and 0.75 mcg/m2 vincristine according to the National Wilms Tumor Study 4 protocol. Weekly measurements of renal size by ultrasound and gross specimens at sacrifice at age 11 weeks were examined and weekly laboratory studies were recorded. Growth rates of renal length and volume were evaluated by linear regression analysis. Terminal renal length and volume were compared between groups.

RESULTS

Mean slope plus or minus standard deviation of the rate of growth in length in the control and chemotherapy groups was 0.067 +/- 0.004 and 0.074 +/- 0.011, respectively (p < or = 0.148, not statistically significant). Mean slope of growth in volume was 1.401 +/- 0.240 versus 1.642 +/- 0.456 (p < or = 0.252), average terminal renal length was 10.71 +/- 1.02 versus 11.58 +/- 1.03 cm (p < or = 0.13, not significant) and mean final volume was 128.67 +/- 32.41 versus 137 +/- 32.52 cc (p < or = 0.65). No differences in final serum creatinine levels were noted.

CONCLUSIONS

Chemotherapy for Wilms tumor did not adversely affect contralateral renal growth or function in a nephrectomized piglet model.

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.

Atrial natriuretic peptide inhibits mesangial cell proliferation induced by early postnephrectomy serum

Rat kidney mesangial or tubular cells were grown in tissue culture medium supplemented with sera of 20 sham-operated vs. 20 nephrectomized Charles River rats. Each cell sample was grown with or without addition of atrial natriuretic peptide (ANP) to the medium. ANP completely abolished the growth stimulatory effect of postnephrectomy serum [i.e., effect of renotropic factor(s) present in the serum] on mesangium cells. Tubular cell proliferation was unchanged. We propose that interaction between renotropin and atrial natriutetic peptide activity might be one of the possible mechanisms regulating compensatory renal growth following nephrectomy.

Urinary protein/creatinine index in follow up of patients with Wilms' tumour after nephrectomy

The protein/creatinine index (p/c) was determined in early morning urine (EMU) samples from available patients with Wilms' tumour who had had a nephrectomy and whose diagnosis had been made between January 1970 and December 1989. Clinical details were obtained by case note review. Results were obtained from 36 boys and 40 girls. The mean interval between nephrectomy and measurement of the EMUp/c was 9.0 years (2-23). Eleven patients had a EMUp/c greater than 20 mg/mmol (normal range less than 20). Of the 11 patients with proteinuria, there were in addition to nephrectomy other adverse features including bilateral tumours, treatment with nephrotoxic drugs, and dysplastic kidneys. Renal dysfunction seems most likely to occur where there are adverse factors in addition to unilateral nephrectomy. There was a significant correlation between the glomerular filtration rate and the EMUp/c, and it is thought that this is a simple tool which can be used for the regular monitoring of renal function in these patients.

Increased insulin-like growth factor-II tissue concentrations during compensatory kidney growth in infantile rats

Insulin-like growth factor (IGF)-I and IGF-II serum and kidney tissue concentrations were measured in compensatory kidney growth in infantile and adult rats. We hypothesized that the known switch from IGF-II in fetal life to IGF-I in adult life may be responsible for the different modes of compensatory kidney growth, which are mainly characterized by hyperplasia in infantile rats and hypertrophy in adult rats. While IGF-I serum concentrations increased with age in infantile rats, kidney tissue concentrations of IGF-I showed a similar increase in both age groups after uninephrectomy. In adult rats, serum and kidney tissue concentrations of IGF-II were unchanged by uninephrectomy. In infantile rats, however, a significant increase in both serum and kidney concentrations of IGF-II was observed with a maximum at day 5 after uninephrectomy. To investigate if compensatory kidney growth is dependent on hyperperfusion of the remnant kidney, the left renal artery was clipped in infantile rats. The clipped kidney showed growth retardation despite normal kidney tissue concentrations of IGF-I and IGF-II. The contralateral kidney was enlarged and IGF-II kidney concentrations were elevated. However, animals with one clipped kidney and nephrectomy of the contralateral kidney showed compensatory kidney growth of the clipped kidney combined with increased IGF-II kidney tissue concentrations. We conclude that IGF-II mainly promotes compensatory kidney growth in infantile rats by hyperplasia. Hyperperfusion of the remnant kidney seems to be unnecessary for initiation of compensatory kidney growth.

Prognosis of children with solitary kidney after unilateral nephrectomy

The clinical course of 138 children who underwent unilateral nephrectomy and had a normal contralateral kidney at the time of nephrectomy was reviewed. The diagnosis leading to nephrectomy included obstructive uropathy in 46% of the cases, reflux or pyelonephritis in 30%, Wilms tumor in 15%, hypertension in 4%, dysplastic kidney in 2% and trauma in 2%. Mean age at nephrectomy was 7.3 years and median followup was 24.7 years. Of the 138 patients 121 (88%) are well and 17 died, including 14 secondary to metastatic Wilms tumor and 1 of renal failure. Survival of nonWilms tumor patients was similar to that of an age-matched control group. In 30 patients 24-hour creatinine clearance and 24-hour urinary protein excretion were measured. Proteinuria (greater than 150 mg./24 hours) was found in 8 of the 30 patients (27%) (p less than 0.001), renal insufficiency developed in 9 (30%) (p less than 0.0001) and hypertension occurred in 10% (p greater than 0.10). Children with an acquired solitary kidney are at increased risk for proteinuria and renal insufficiency.

Compensatory hypertrophy effectively assesses the degree of impaired renal function in unilateral renal disease

A series of 66 children with unilateral renal disease and normal total renal function were reviewed with the aim of determining whether clinically detectable compensatory hypertrophy indicated severe contralateral renal impairment. The proportion of total renal function that was contributed by each kidney was determined using isotope renography (99mTc-DTPA for 46 children, 99mTc-DMSA for 20). Kidney length was measured from plain abdominal radiographs or intravenous urograms and hypertrophy was expressed as the renal size index (RSI). Of 37 kidneys with a RSI greater than 2 standard deviations from the mean, 36 had less than 15% of total function in the contralateral diseased kidney. Kidneys with less than 10 or 15% of total renal function could be selected with 97 or 80% sensitivity and 84 or 97% specificity, respectively, using the same RSI selection level.

The effect of unilateral nephrectomy on the subsequent radiation response of the pig kidney

The left kidney of 14 Large White female pigs, approximately 14 weeks of age, was surgically removed. Thirty weeks after unilateral nephrectomy (UN) the remaining kidney was irradiated with a single dose of between 11.9 and 15.6 Gy of 60Co gamma-rays; three pigs received sham irradiation. Following irradiation glomerular filtration rate (GFR), effective renal plasma flow (ERPF) and haematocrit (Hct) were determined for up to 48 weeks after irradiation. Irradiation resulted in a dose-dependent decline in GFR, evident 8 weeks after irradiation. This was followed by a gradual improvement in GFR, although after doses of 14.0 Gy GFR remained below control values throughout the study. A similar pattern of response was seen in terms of ERPF, but this was not dose-related. Doses of greater than or equal to 14.0 Gy also caused a significant reduction (p less than 0.001) in Hct within 4-8 weeks. Minimal levels were evident 16 weeks after irradiation; Hct then increased, but remained below preirradiation values. Dose-effect curves were obtained by determining the percentage of irradiated kidneys which showed a greater than or equal to 50% reduction in GFR and ERPF, fitted by probit analysis, and ED50 values (+/- SE) were calculated for each parameter. The ED50 values for GFR and ERPF were 14.49 +/- 0.27 Gy and 12.56 +/- 0.98 Gy, respectively. These values were not significantly different from those obtained from intact age-matched pigs in which the right kidney alone was irradiated; UN did not compromise or alter the radiation response of the kidney to irradiation. However, the ED50 values obtained for the UN pigs were significantly greater (p less than 0.001) than the values of 9.76 +/- 0.17 Gy and 6.19 +/- 0.93 Gy, seen for GFR and ERPF in intact age-matched pigs in which both kidneys were irradiated. Thus although both experimental situations involved irradiating the entire renal tissue, the relative radiosensitivity of the kidneys varied considerably. These findings show that the radiosensitivity of the pig kidney can vary markedly, depending on the physiological status of the kidney at the time of irradiation.

Renal growth and function 11-28 years after treatment of Wilms' tumour

In order to obtain more information on the long-term effects of treatment of Wilms' tumour we investigated 30 subjects treated at the Children's Hospital between 1960 and 1976. All had been nephrectomized and in 4 the length of the remaining kidney was subnormal. In the other subjects kidney length was related to follow up time and age at follow up. Blood pressure was elevated in 5 subjects. Urinary albumin excretion deviated only slightly from normal. Tubular functions were well preserved in all subjects. In this small series we were unable to establish any relation between the abnormalities observed and the treatment given. Our results suggest that, despite wide interindividual variation those who survive Wilms' tumours seldom have long-term renal complications.

Hyperfiltration-induced renal injury in normal man: myth or reality

Current knowledge fails to support the notion that adaptive hyperfiltration of the remnant kidney after donor nephrectomy is deleterious. Rather than being maladaptive, hyperfiltration appropriately compensates for the loss of functional renal mass. Accordingly, most kidney donors can be expected to maintain a stable level of renal function without proteinuria or hypertension. Essential to this is proper selection of donors for nephrectomy and exclusion of high risk potential donors, bearing in mind the fact that apparently healthy, asymptomatic relatives of end stage renal disease patients are prone to the same disease processes that inflict the general population and have a higher risk of underlying renal disease.

Natural history of fetal and neonatal hydronephrosis

Since pyelocalicectasis alone is common in fetuses, we reviewed reports of fetal hydronephrosis that resolved spontaneously or at birth. Severe fetal hydronephrosis with calicectasis or parenchymal thinning rarely resolves spontaneously before or after birth. We also reviewed the clinical and experimental literature on renal hypertrophy. After unilateral nephrectomy in neonatal animals or after birth with congenital absence of one kidney in humans, the remaining kidney hypertrophies very quickly. In infants and young animals, the eventual size of the remaining kidney is inversely proportional to the age at which one kidney is lost. This improvement in residual renal function seen after renal loss in infancy, compared with older children, itself constitutes a strong argument for early relief of obstruction. If contralateral renal hypertrophy has occurred, the treated damaged kidney may resume growth in parallel with its hypertrophied mate but does not become as large or recover normal potential for growth. In other words, if correction of a unilateral obstruction is deferred until contralateral hypertrophy occurs, the obstructed kidney then has less potential for recovery of function.

An approach to protein restriction in children with renal insufficiency

Children with mild to moderate renal insufficiency may be at an increased risk for developing glomerulosclerosis and subsequent renal failure. Low protein diets (LPD) have been shown to delay the progression of renal insufficiency in laboratory animals and may be of benefit in adult humans. The nutritional costs of a LPD in adults are reportedly minimal. We review the protein and caloric requirements of growing children and discuss the potential harmful effects and benefits of an LPD in this population. We also discuss dietary adherence and the difficulty of designing an LPD for children. We conclude that the protein content of a typical American diet can safely be reduced to, but not below, the recommended daily allowance for protein if diets are carefully planned, patients and their parents extensively counseled, and if dietary supplements are given to help meet the caloric and vitamin-mineral nutrient needs of growing children. In addition, ongoing nutritional assessment, counseling, and frequent monitoring of growth, diet and biochemical indicators of protein status are essential for maintaining the health of these children.

The solitary kidney: a model of chronic hyperfiltration in humans

Reduction of renal mass (11/12) in rats leads to progressive azotemia, proteinuria, and hypertension. Less extensive renal ablation resulting from uninephrectomy also accelerates the progression of focal glomerulosclerosis (FGS) induced by experimental diabetes, renal irradiation, aminonucleoside nephrosis, or aging. The consequence of the absence of one kidney in man are examined in three different clinical situations. Unilateral renal agenesis seems to predispose to the development of FGS, but most reports include isolated cases and the true incidence of FGS is not known. The solitary kidney following uninephrectomy for acquired unilateral disease undergoes a compensatory rise in glomerular filtration rate (GFR) that remains stable for several decades. Finally, kidney donors followed for over 2 decades show unimpaired GFR, elevated at 70% to 80% of the normal (two-kidney) GFR. Some donors develop mild, nonprogressive proteinuria. Their incidence of hypertension matches that in the control population. Thus, hyperfiltration secondary to 50% reduction of renal mass in humans does not lead to loss of function of the remaining parenchyma.

Kidney function in adults born with unilateral renal agenesis or nephrectomized in childhood

We have evaluated the long-term prognosis in an unselected group of adult patients either uni-nephrectomized in childhood because of hydronephrosis or born with unilateral renal agenesis. Thirty-six patients aged 7-47 years were followed for 7-40 years. In 23 control subjects aged 20-47 years the glomerular filtration rate (GFR) and the p-aminohippuric acid clearance (CPAH) did not change significantly with age. In patients with a single kidney the size of that kidney was larger and GFR and CPAH were higher than single kidney values in control subjects. However, in patients with a single kidney since childhood the GFR and the CPAH declined slowly but significantly during the follow-up period. Significant microalbuminuria occurred in 47% of the patients with a single kidney and was more frequent with a longer follow-up period. No patient had renal insufficiency or a marked increase in arterial blood pressure. We conclude that in patients with a single kidney since childhood the long-term prognosis is good, but the late decrease in GFR and increase in albumin excretion may indicate a moderate risk for premature renal damage.

Development of focal glomerulosclerosis after unilateral nephrectomy in infant rats

Rats unilaterally nephrectomized in infancy (Nx5) or in adulthood (Nx55) and fed a normal (21%) protein diet were studied at 2, 3 and 6 months after surgery with regard to glomerular filtration rate (GFR) and the development of both albuminuria and focal glomerulosclerosis (FGS) in the remnant kidney. Nx rats were compared with sham-operated animals (S) of corresponding age. The incidence of FGS never exceeded 1.4% in S rats. In Nx5 rats the incidence of FGS was not increased at 2 and 3 months after surgery whereas it was significantly higher (range 10%-27%) than in S rats 6 months after surgery. Urinary albumin excretion was significantly increased in Nx5 rats 2 months after surgery and was even higher 6 months after surgery. In Nx55 rats the incidence of FGS was the same as in Nx5 rats 2, 3 and 6 months after surgery, but urinary albumin excretion was significantly lower than in Nx5 rats 6 months after surgery. The GFR expressed per unit of body weight decreased in both Nx5 and S5 rats from 2 to 6 months, but the decrease was more pronounced in Nx5 rats than in S5 rats. The GFR factored by kidney weight was significantly lower in Nx5 than in any of the other groups at the 6-month follow-up study. We conclude that, as in adults, when unilateral nephrectomy is performed in infancy, FGS will develop in the remnant kidney. More pronounced albuminuria and reduction of GFR may indicate that the glomerular lesion is more severe in rats nephrectomized in infancy than in adulthood.

A comparative study of size and function of the remnant kidney in patients nephrectomized in childhood for Wilms' tumor and hydronephrosis

To obtain more information about the natural history of compensatory renal hypertrophy beginning in childhood we traced those who were nephrectomized in childhood for Wilm's tumor (W) and hydronephrosis (Hn) between 1950 and 1978 at one department of surgery in Stockholm. All W patients had received treatment that suppresses cellular division. None of the patients were in renal failure or treated with antihypertensive drugs. All the patients in the follow-up study (22 W, 15 Hn) had a normal contralateral kidney at nephrectomy. Five healthy adults served as controls. The kidney was enlarged in both Hn (142%) and W (125%), but significantly larger in Hn than in W. Renal compensatory growth in W was retarded during the first two years after nephrectomy. The glomerular filtration rate (GFR) was 92% of control in Hn and 82% of control in W. The GFR did not seem to decline with a longer follow-up time in any of the groups. PAH clearance was the same in Hn and W. Albumin excretion was significantly higher in Hn than in W, but not significantly higher in W than in controls. The highest albumin excretion rates were found among the Hn patients with long follow-up time. The results suggest that the large increases in size and function that follow childhood nephrectomy can be blunted by antimitotic agents.

Renal involvement in the Laurence-Moon-Biedl syndrome. Functional and radiological studies

The renal abnormality of the Laurence-Moon-Biedl syndrome (LMBS) was investigated in six patients. The glomerular filtration rate (CIn) and the effective renal plasma flow (CPAH) were evaluated by standard clearance techniques and the single injection method, and the maximal concentration capacity was estimated by the ddAVP test. The kidney surface area and length were related to the body surface area, as well as the lumbar vertebrae L1-L3, and the relationship with the GFR was studied. All six patients showed renal abnormalities: Five had small kidneys with reduced GFR and concentrating ability, and one had hyperaminoaciduria (but normal kidney size). Two patients developed terminal renal failure (one of them was successfully transplanted), illustrating the progressive character of the renal lesion. Three of the patients had had recurrent urinary tract infections, but the radiological changes of the kidneys were of the same character as in the others (symmetrical and irregular parenchymal reduction, and blunting and clubbing of the calyces). Since renal abnormalities, with considerable risk for progression to terminal renal failure, are common in the LMBS, regular urine cultures and blood pressure measurements are probably of great importance.

Focal sclerosis of hypertrophied glomeruli in solitary functioning kidneys of humans

Morphometric data on glomerular size are presented on three patients with solitary functioning kidneys and one with bilateral oligomeganephronic hypoplasia. Renal biopsy of each of two patients with a congenitally absent kidney (unilateral renal agenesis) and a patient with oligomeganephronie, all with proteinuria and renal insufficiency, reveal increases of mean glomerular diameters of at least 1.75X and mean glomerular volumes greater than 5X. These dimensions, which are in the range of maximal increases recorded for man, are associated in all three biopsies with focal sclerosis of the hypertrophied glomeruli. By contrast, the functionally fully-compensated solitary kidney of a patient who lost function of the contralateral kidney from acquired disease, is characterized by the absence of focal glomerulosclerosis and by glomerular enlargement of significantly lesser degree (increased mean diameter 1.24X and mean volume less than 2X). These observations correlate glomerular injury with glomerular size and suggest that in the setting of reduced nephron numbers, nephron destruction via focal glomerulosclerosis may be initiated when compensatory glomerular hypertrophy has reached its limits.

Renoprival growth following treatment of unilateral Wilms' tumour

The renal growth pattern following uninephrectomy for Wilms' tumour was analysed in 18 boys and 18 girls by means of a comparison between renal parenchymal and body surface area. No straightforward correlation was noted between age at nephrectomy, chemo- and radiation therapy applied, and subsequent renoprival dimensions. Five years on average after operation, a mean renal size corresponding to approximately 125 per cent of the normal for one of two healthy kidneys was recorded. However, wide variations in size were observed, but only 10 patients had a compensatory growth of the remaining kidney equivalent to that seen in patients nephrectomized for unilateral, non-malignant renal disease.

Increased fractional excretion of phosphate and beta 2-microglobulin in unilateral renal disease

Following progressive nephron loss tubular reabsorption in the remaining nephrons will fall to preserve solute and electrolyte excretion. We have examined the fractional excretion (FE) of phosphate, sodium, beta 2-microglobulin (beta 2M) and tubular glucose reabsorption (T glucose) in children with unilateral renal disease to find 1) the threshold for this response and 2) whether intrinsic renal mechanisms can elicit this response. Separate renal function studies were performed using unilateral ureteral compression. Total glomerular filtration rate (GFR) was 93.7 +/- 2.99 ml/1.73(m2)-1 X min-1, and 110.25 +/- 5.40 in control children. GFR in the scarred kidney (SK) was 22.4 +/- 2.46 and in the contralateral kidney (CIK) 67.2 +/- 4.60 ml X 1.73 (m2)-1 X min-1. The kidney area was reduced in proportion to GFR in SK. FE phosphate and beta 2M were significantly higher in SK than in CIK (sign test), but absolute values for FE phosphate and beta 2M were not higher in SK than in control kidneys. FE sodium and T glucose were the same in SK and CIK.

CONCLUSION

Following moderate unilateral reduction of GFR selective depression of tubular reabsorption can occur without extrarenal impulses.

Growth of renoprivals following uninephrectomy for Wilms' tumour: application and suitability of a method of assessment

In an attempt to evaluate the long-term renoprival growth in patients uni-nephrectomized for Wilms' tumour, renal length was related to the length of the lumbar segment L1-L3. The results of this study indicated that spinal growth retardation, secondary to applied adjuvant treatment, invalidated employment of the method for this particular purpose. A computerized analysis showed no straight-forward correlation between age at operation, chemotherapy utilized, irradiation and the post-treatment renoprival growth as established by substitution of the observed L1-L3 length with a mathematically corrected value. Emergent figures exclude significant compensatory growth of the remaining kidney.

Long-time effect of large vesicoureteral reflux with or without urinary tract infection

In children more than one year old the growth rate of the renal parenchyma is delayed if the kidney has a large reflux-ureter and is exposed to urinary tract infection. The growth rate of the parenchyma is normal, if the kidney has a large reflux-ureter but no infection. However, since moderate reduction of the renal parenchyma is often observed in patients with large reflux-ureter but without a history of urinary tract infection, it is concluded that a large reflux may cause back pressure injury on the kidney during infancy but, in children more than one year old, will cause renal growth retardation and renal scarring only be predisposing to pyelonephritis.

Size of the unaffected kidney in children with unilateral hydronephrosis

Children with unilateral hydronephrosis, but without evidently decreased excretion of urographic contrast medium, generally had enlargement of the unaffected mate kidney, indicating reduced function of the hydronephrotic kidney.

Renal compensatory hypertrophy in children with unilateral renal disease

Kidney parenchymal size was estimated on urograms from 22 children with unilateral vesico-ureteral reflux (VUR), 14 children with bilateral VUR and seven children with unilateral heminephrectomy. In the bilateral VUR group, one kidney was roentgenologically normal and the other was growth-retarded. The GFR was estimated in 19 of the children. The age of the children was 3-17 years and all had a history of urinary tract infection. The size of the smaller kidney varied between 33-97% of normal. Children in the unilateral VUR group with a small kidney due to scarring and/or growth retardation showed a varying degree of compensatory hypertrophy in the contralateral kidney, which was proportional to the parenchymal reduction. This compensation was inhibited in the bilateral VUR group. There was a positive correlation between the GFR and kidney size.

Renal functional adaptation in the remnant kidney in patients with renal agenesis and in patients nephrectomized in childhood

The renal response to volume expansion was determined in four patients with renal hypertrophy due to unilateral renal agenesis (URA) and in four patients with renal hypertrophy due to nephrectomy (Nz). Four healthy controls were also studied. The studies were performed during water diuresis and following i.v. infusion of isotonic saline solution. Conventional clearance techniques were used. GFR and PAH clearence were increased to about the same extent in Nz and in URA. Fractional Na+ excretion was highest in the Nz group and lowest in the control group. It was higher in the Nz group than in the URA group. Fractional water excretion (V/GFR) and free water clearance (CH2O) were also determined and the results indicate that the high fractional excretion of Na+ from the hypertrophied kidney can be attributed to reduced fractional reabsorption of filtrated Na+ both in the proximal and the distal tubules. The fractional Na+ reabsorption in the distal tubule appears to be higher in URA than in Nz. It is concluded that glomerular tubular balance for Na+ is more similar to that found in healthy controls if the stimulus to hypertrophy occurs prenatally than if it occurs postnatally.