Renal length and inulin clearance in the radiologically normal single kidney

Towards adulthood with a solitary kidney

Around 1/1000 people have a solitary kidney. Congenital conditions mainly include multicystic dysplastic kidney and unilateral renal aplasia/agenesis; acquired conditions are secondary to nephrectomy performed because of urologic structural abnormalities, severe parenchymal infection, renal trauma, and renal or pararenal tumors. Children born with congenital solitary kidney have a better long-term glomerular filtration rate than those with solitary kidney secondary to nephrectomy later in life. Acute and chronic adaptation processes lead to hyperfiltration followed by fibrosis in the remnant kidney, with further risk of albuminuria, arterial hypertension, and impaired renal function. Protective measures rely on non-pharmacological renoprotection (controlled protein and sodium intake, avoidance/limitation of nephrotoxic agents, keeping normal body mass index, and limitation of tobacco exposure). Lifelong monitoring should include blood pressure and albuminuria assessment, completed by glomerular filtration rate (GFR) estimation in case of abnormal values. In the absence of additional risk factors to solitary kidney, such assessment can be proposed every 5 years. There is no current consensus for indication and timing of pharmacological intervention.

The clinical characteristics of Chinese patients with unilateral renal agenesis

BACKGROUND

We aimed to investigate the clinical characteristics of Chinese patients with unilateral renal agenesis.

METHODS

We enrolled patients with unilateral renal agenesis diagnosed radiologically at the Department of Nephrology from January 2008 to January 2016. Patients with a solitary kidney due to nephrectomy or renal atrophy due to secondary factors were excluded. Clinical data were recorded and analyzed.

RESULTS

In this study, 118 Chinese patients with unilateral renal agenesis were recruited, and the gender ratio (male/female) was 1.11:1. A total of 14 (11.9%) patients had additional abnormalities, 15 (12.7%) had a family history, and 30 (25.4%) presented with renal insufficiency. Kidney length, serum creatinine level and estimated glomerular filtration rate were significantly different between patients with and without family history (P < 0.05, respectively). Gender showed a significant difference between patients with and without other abnormalities. Kidney length and the incidence of proteinuria, hematuria, hypertension, and hyperuricemia were significantly different between patients with and without renal insufficiency. Logistic regression analysis revealed that family history was associated with severe renal failure (OR = 7.11, 95% CI 1.52-33.25).

CONCLUSION

Renal insufficiency is common in patients with unilateral renal agenesis. Patients with renal insufficiency have shorter kidney lengths and a higher incidence of proteinuria, hypertension, hematuria, and hyperuricemia. Family history is considered a risk factor for severe renal failure.

Nephron number, hypertension, and CKD: physiological and genetic insight from humans and animal models

The kidneys play a vital role in the excretion of waste products and the regulation of electrolytes, maintenance of acid-base balance, regulation of blood pressure, and production of several hormones. Any alteration in the structure of the nephron (basic functional unit of the kidney) can have a major impact on the kidney's ability to work efficiently. Progressive decline in kidney function can lead to serious illness and ultimately death if not treated by dialysis or transplantation. While there have been numerous studies that implicate lower nephron numbers as being an important factor in influencing susceptibility to developing hypertension and chronic kidney disease, a direct association has been difficult to establish because of three main limitations: 1) the large variation in nephron number observed in the human population; 2) no established reliable noninvasive methods to determine nephron complement; and 3) to date, nephron measurements have been done after death, which doesn't adequately account for potential loss of nephrons with age or disease. In this review, we will provide an overview of kidney structure/function, discuss the current literature for both humans and other species linking nephron deficiency and cardio-renal complications, as well as describe the major molecular signaling factors involved in nephrogenesis that modulate variation in nephron number. As more detailed knowledge about the molecular determinants of nephron development and the role of nephron endowment in the cardio-renal system is obtained, it will hopefully provide clinicians the ability to accurately identify people at risk to develop CKD/hypertension and lead to a shift in patient care from disease treatment to prevention.

Growth and function in childhood of a normal solitary kidney from birth or from early infancy

BACKGROUND

Children with a solitary kidney (SK) have an increased long-term risk of hypertension, albuminuria and glomerulosclerosis. In this study, we assessed the early signs of impaired glomerular filtration in children with a SK from birth or from early infancy.

METHODS

Renal growth and function at ages 4-15.5 years were studied in 38 children with SK and 40 matched control subjects in terms of accelerated growth.

RESULTS

The systolic/diastolic blood pressure Z-scores (p = 0.01/<0.05) and the resistance index (RI) of the arcuate arteries (p = 0.05) were higher in the children with SK. Creatinine clearance and 24-h protein and albumin urinary excretion showed no difference. All but seven children with SK had 99mTc diethylene-triamine pentaacetic acid glomerular filtration rate values of >80 ml/min/1.73 m(2). An independent positive correlation was found between length of the follow-up time and 24-h albumin urinary excretion (β = 0.54, p < 0.01). Accelerated postnatal growth was positively related with kidney volume (β = 0.35, p < 0.05).

CONCLUSIONS

Among our patient cohort, renal function was well preserved at ages 4-15.5 years in children who were born with a SK. However, both their higher blood pressure and RI and the correlation of 24-h albumin urinary excretion with length of follow-up time underline the need for monitoring to detect early signs of glomerular hyperfiltration and, if necessary, implement timely intervention. SK hypertrophy was found to be correlated with postnatal growth.

Compensatory renal growth after unilateral or subtotal nephrectomy in the ovine fetus

BACKGROUND

Clinical and experimental studies show that unilateral (1/2Nx) and subtotal nephrectomy (5/6Nx) in adults result in compensatory renal growth without formation of new nephrons. During nephrogenesis, the response to renal mass reduction has not been fully investigated.

METHODS

Ovine fetuses underwent 1/2Nx, 5/6Nx, or sham surgery (sham) at 70 d of gestation (term: 150 d), when nephrogenesis is active. At 134 d, renal function was determined, fetuses were killed, and kidneys were further analyzed at the cellular and molecular levels. Additional fetuses subjected to 5/6Nx were killed at 80 and 90 d of gestation to investigate the kinetics of the renal compensatory process.

RESULTS

At 134 d, in 1/2Nx, a significant increase in kidney weight and estimated glomerular number was observed. In 5/6Nx, the early and marked catch-up in kidney weight and estimated glomerular number was associated with a striking butterfly-like remodeling of the kidney that developed within the first 10 d following nephrectomy. In all groups, in utero glomerular filtration rates were similar.

CONCLUSION

Compensatory renal growth was observed after parenchymal reduction in both models; however, the resulting compensatory growth was strikingly different. After 5/6Nx, the remnant kidney displayed a butterfly-like remodeling, and glomerular number was restored.

The relationships between renal compensatory hypertrophy etiologic factors and anthropometric development in the pediatric age group

OBJECTIVE

To evaluate the factors associated with compensatory hypertrophy in the functional kidneys of children.

METHODS

The medical files of patients with a solitary functional kidney were reviewed retrospectively. Data regarding anthropometric measurements, functional renal length, functional renal length of standard deviation score (SDS) of functional kidney at diagnosis, and end of follow-up were obtained. Patients were divided into 2 groups, those with a unilateral kidney function of <10% (hypoplasia, dysplasia, and atrophy, group 1) and those with a solitary kidney (agenesis, and multicystic dysplastic kidney, group 2).

RESULTS

A total of 126 patients (70 boys) were evaluated. Both the sizes of the functional kidney and functional kidney SDS values at diagnosis were greater in group 1 relative to group 2. At the end of the follow-up period, anthropometric values including functional kidney size were higher in group 2. Functional kidney size of 2 SDS above the normal was mostly predictive at age 17.5 months (odds ratio [OR] 5.06) and at a body height of 82 cm (OR 5.57).

CONCLUSION

The most determining factors for renal length SDS values were age and height. Solitary kidneys complete compensatory hypertrophy by 17.5 months of age, and after that their growth continues in parallel to normal growth.

Unilateral renal agenesis: a systematic review on associated anomalies and renal injury

BACKGROUND

Unilateral renal agenesis (URA) is associated with other congenital anomalies of the kidney and urinary tract (CAKUT) and extra-renal anomalies. However, the reported prevalences of these anomalies are highly variable. We estimated the prevalence of associated CAKUT and extra-renal anomalies in patients with URA. Furthermore, we determined the prevalence of renal injury in URA patients.

METHODS

We conducted a systematic review of English and non-English articles using PubMed and Embase.com. Included studies reported at least one of the following items: incidence of URA, gender, side of URA, prenatal diagnosis, performance of micturating cystourethrogram, associated CAKUT, urinary tract infection or extra-renal anomalies. Studies that described a mean/median glomerular filtration rate (GFR) and proportions of patients with hypertension, micro-albuminuria or a decreased GFR were also included.

RESULTS

Analyses were based on 43 included studies (total number of patients: 2684, 63% male). The general incidence of URA was 1 in ∼2000. Associated CAKUT were identified in 32% of patients, of which vesicoureteral reflux was most frequently identified (24% of patients). Extra-renal anomalies were found in 31% of patients. Hypertension could be identified in 16% of patients, whereas 21% of patients had micro-albuminuria. Ten per cent of patients had a GFR<60 mL/min/1.73 m2;.

CONCLUSIONS

These aggregate results provide insight in the prevalence of associated anomalies and renal injury in patients with URA. Our systematic review implicates that URA is not a harmless malformation by definition. Therefore, we emphasize the need for clinical follow-up in URA patients starting at birth.

Risk factors for renal injury in children with a solitary functioning kidney

OBJECTIVE

The hyperfiltration hypothesis implies that children with a solitary functioning kidney are at risk to develop hypertension, proteinuria, and chronic kidney disease. We sought to determine the presenting age of renal injury and identify risk factors for children with a solitary functioning kidney.

METHODS

We evaluated 407 patients for signs of renal injury, defined as hypertension, proteinuria, an impaired glomerular filtration rate, and/or the use of renoprotective medication. Patients were subdivided on the basis of type of solitary functioning kidney and the presence of ipsilateral congenital anomalies of the kidney and urinary tract (CAKUT). The development of renal injury was analyzed with Kaplan-Meier analysis. Risk factors were identified by using logistic regression models.

RESULTS

Renal injury was found in 37% of all children. Development of renal injury increased by presence of ipsilateral CAKUT (odds ratio [OR] 1.66; P = .04) and age (OR 1.09; P < .001). Renal length was inversely associated with the risk to develop renal injury (OR 0.91; P = .04). In all patients, the median time to renal injury was 14.8 years (95% confidence interval 13.7-16.0 years). This was significantly shortened for patients with ipsilateral CAKUT (12.8 years, 95% confidence interval 10.6-15.1 years).

CONCLUSIONS

Our study determines independent risk factors for renal injury in children with a solitary functioning kidney. Because many children develop renal injury, we emphasize the need for clinical follow-up in these patients starting at birth.

Renal functional reserve in children with apparently normal congenital solitary functioning kidney

OBJECTIVE

The aim of the study was to investigate renal functional reserve (RFR) and to assess its relationship with serum cystatin C and blood pressure in children with apparently normal congenital solitary functioning kidney (SFK).

MATERIAL AND METHODS

RFR was obtained from the difference of endogenous creatinine clearance (CrCs) before and after a meat-free oral protein load (OPL) in the patients who were pre-treated with cimetidine. Serum cystatin C and urinary protein excretion were determined before and after OPL.

RESULTS

Among 22 patients (13 boys), aged 9.5 ± 4.3 years, 72.7% had increased serum cystatin C, and 54.5% had decreased RFR. Following OPL, CrCs and urine creatinine increased, while serum creatinine and cystatin C remained unchanged. The multiple regression analysis demonstrated that cystatin C could predict more than 90% of RFR variability.

CONCLUSION

Half of the patients with apparently normal SFK had decreased RFR. Serum cystatin C is one of the best predictors of RFR.

Renal injury in children with a solitary functioning kidney--the KIMONO study

BACKGROUND

Children with a solitary functioning kidney (SFK) have an increased risk of developing hypertension, albuminuria and chronic kidney disease in later life. This renal injury is hypothesized to be caused by glomerular hyperfiltration that follows renal mass reduction in animal studies. Furthermore, children with an SFK show a high incidence of congenital anomalies of the kidney and urinary tract (CAKUT), which could further compromise renal function.

METHODS

A retrospective study of renal injury markers was performed in 206 children, divided into groups based on the origin of SFK [primary (congenital) SFK (n = 116) and secondary SFK (n = 90)]. Data on ipsilateral CAKUT were stratified separately. For blood pressure, albuminuria and glomerular filtration rate, longitudinal models were additionally developed using generalized estimated equation analysis.

RESULTS

Renal injury, defined as the presence of hypertension and/or albuminuria and/or the use of renoprotective medication, was present in 32% of all children with an SFK at a mean age of 9.5 (SD 5.6) years. Children with ipsilateral CAKUT had higher proportions of renal injury (48.3 versus 24.6%, P < 0.05). Furthermore, longitudinal models showed a decrease in glomerular filtration rate in both groups from the beginning of puberty onwards.

CONCLUSIONS

This large cohort study demonstrates that renal injury is present in children with an SFK at a young age, whereas our longitudinal models show an increased risk for chronic kidney disease in adulthood. Renal injury is even more pronounced in the presence of ipsilateral CAKUT. Therefore, we underline that clinical follow-up of all children with an SFK is needed.

Congenital versus acquired solitary kidney: is the difference relevant?

BACKGROUND

Serious concerns have risen during the last decades regarding the potential role of solitary kidney (SK) in promoting systemic hypertension, proteinuria and glomerulosclerosis. The aim of the study was to assess mid- and long-term outcome of children with SK, with special highlight on the differential functional outcome of congenital and acquired forms of SK.

METHODS

Ninety-seven patients (43 females) aged from 2.9 to 25 years with radiologically normal SK were divided into two groups depending on whether they had a congenital (CSK, n = 44) or an acquired SK (ASK, n = 53). Mean follow-up time with SK was 8.3 ± 3.2 and 9.1 ± 4.4 years, respectively (P = NS). Blood pressure (BP), glomerular filtration rate (GFR) measured by inulin clearance, and microalbuminuria were assessed in all patients.

RESULTS

Two children (2%), one in each group, had systemic hypertension confirmed by 24-h ambulatory BP monitoring, and 17 (17.5%) had a significant microalbuminuria (8 in CSK and 9 in ASK, P = NS). The overall mean GFR was 100.6 ± 15 mL/min/1.73 m(2) and was found to be inversely correlated with age and follow-up time. Seven children had a GFR <80 mL/min/1.73 m(2), all had been nephrectomized in early childhood. Interestingly, GFR was higher in CSK than in ASK group (107.2 vs. 95.2 mL/min/1.73 m(2), P < 0.01) and was negatively related to follow-up time only in the latter but not in the former group.

CONCLUSIONS

In the light of these results, it appears that renal function in children with SK is well preserved in short and medium term, but it seems to decline gradually with longer periods of follow-up, particularly in ASK, thus assuming a better functional adaptation in CSK. Both conditions remain yet risky and predispose children to a greater incidence of hypertension and renal impairment in later life. Thereby, careful screening should be proposed throughout childhood to detect early signs of glomerular hyperfiltration and prevent its progression to more serious complications.

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.

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.

Renal outcome of children with one functioning kidney from birth. A study of 99 patients and a review of the literature

In patients with a single functioning kidney, renal function was assessed at regular intervals over a period of 10 years. Serum creatinine, glomerular filtration rate (GFR), blood pressure, and urinary protein-creatinine ratio were assessed at the age of 2, 5 and 10 years. Between January 1980 and December 2005, 99 such patients were diagnosed in the first year of life. They were divided into three groups: A, patients with multicystic kidney disease and a normal contralateral kidney (n = 36); B, patients with a normal solitary kidney without uropathy (n = 20); and C, patients with obstructive uropathy and one nonfunctioning kidney (n = 43). Serum creatinine levels increased significantly with increasing age in every group. In group C, serum creatinine was significantly elevated compared with group A in all age categories (p = 0.043, p = 0.019, p = 0.001 respectively). Median figures of GFR remained within normal limits over the 10-year period. GFR was significantly lower in group C compared with group A (p = 0.001, p = 0.009, p = 0.019 respectively) and B in all age categories (p = 0.013, p = 0.002, p = 0.016 respectively). There were no changes in blood pressure over time and no differences among the three groups were observed. At the age of 10 years, the patients in group C had a significantly higher median urinary protein-creatinine ratio (p = 0.022) than those in groups A and B. There was also an increasing level of proteinuria with increasing age in group C (p = 0.002). In conclusion, renal function was stable over time in all patients, but children with obstructive uropathy have a lower median GFR and higher serum creatinine level for the whole study period. Hypertension was exceptionally observed in group C, with obstructive uropathy, as was an elevated urinary protein-creatinine ratio.

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.