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

Management of the congenital solitary kidney: consensus recommendations of the Italian Society of Pediatric Nephrology

In recent years, several studies have been published on the prognosis of children with congenital solitary kidney (CSK), with controversial results, and a worldwide consensus on management and follow-up is lacking. In this consensus statement, the Italian Society of Pediatric Nephrology summarizes the current knowledge on CSK and presents recommendations for its management, including diagnostic approach, nutritional and lifestyle habits, and follow-up. We recommend that any antenatal suspicion/diagnosis of CSK be confirmed by neonatal ultrasound (US), avoiding the routine use of further imaging if no other anomalies of kidney/urinary tract are detected. A CSK without additional abnormalities is expected to undergo compensatory enlargement, which should be assessed by US. We recommend that urinalysis, but not blood tests or genetic analysis, be routinely performed at diagnosis in infants and children showing compensatory enlargement of the CSK. Extrarenal malformations should be searched for, particularly genital tract malformations in females. An excessive protein and salt intake should be avoided, while sport participation should not be restricted. We recommend a lifelong follow-up, which should be tailored on risk stratification, as follows: low risk: CSK with compensatory enlargement, medium risk: CSK without compensatory enlargement and/or additional CAKUT, and high risk: decreased GFR and/or proteinuria, and/or hypertension. We recommend that in children at low-risk periodic US, urinalysis and BP measurement be performed; in those at medium risk, we recommend that serum creatinine also be measured; in high-risk children, the schedule has to be tailored according to kidney function and clinical data.

Renal function in children with a congenital solitary functioning kidney: A systematic review

INTRODUCTION

Abnormal renal development that results in lack of function or development of one of two kidneys is known as congenital solitary functioning kidney (CSFK). Two well characterized sub-categories of CFSK are unilateral renal agenesis (URA) and multicystic dysplastic kidney (MCDK). This systematic review sought to evaluate the change in renal function in children ≤18 years old with a CSFK as a result of URA or MCDK.

METHODS

A literature search in MEDLINE and Embase was conducted (1946 to July 13, 2020). All relevant articles were retrieved and evaluated based on pre-selected criteria by two independent researchers. Data was then extracted from variables of interest and conflicts were resolved by a third researcher. The primary outcome was renal function, and the secondary outcomes were proteinuria and hypertension.

RESULTS

Forty-five studies were included, of which 49% (n = 22) were retrospective and/or 58% (n = 26) were cohort studies. A combined total of 2148 and 885 patients were diagnosed with MCDK or URA, respectively. The proportion of children with worsened renal function at follow-up was found to be 8.4% (95% CI: 5.2%-13.4%). Among the studies reporting renal function as a group mean or median at follow-up, 84% (21/25) had a GFR/CrCl above 90 (mL/min/1.73  m²/ml/min). In terms of secondary outcomes, the proportion of children with proteinuria and hypertension was found to be 10.1% (95% CI: 6.9%-14.6%) and 7.4% (95% CI: 5.0%-10.9%), respectively.

CONCLUSION

The risk of developing proteinuria (10.1%), hypertension (7.4%), and/or worsened renal function (8.4%) for children with CFSK as a result of MCDK or URA is low. However, the level of evidence in the literature is weak. Further research is needed to identify the predisposing factors that may differentiate the small subset of children with CSFK at a higher risk of developing adverse renal outcomes.

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.

A clinical predictive model of renal injury in children with congenital solitary functioning kidney

BACKGROUND

Solitary functioning kidney (SFK) is an important condition in the spectrum of congenital anomalies of the kidney and urinary tract. The aim of this study was to describe the risk factors for renal injury in a cohort of patients with congenital SFK.

METHODS

In this retrospective cohort study, 162 patients with SFK were systematically followed up (median, 8.5 years). The primary endpoint was time until the occurrence of a composite event of renal injury, which includes proteinuria, hypertension, and chronic kidney disease (CKD). A predictive model was developed using Cox proportional hazards model and evaluated by c statistics.

RESULTS

Among 162 children with SFK included in the analysis, 132 (81.5%) presented multicystic dysplastic kidney, 20 (12.3%) renal hypodysplasia, and 10 (6.2%) unilateral renal agenesis. Of 162 patients included in the analysis, 10 (6.2%) presented persistent proteinuria, 11 (6.8%) had hypertension, 9 (5.6%) developed CKD stage ≥ 3, and 18 (11%) developed the composite outcome. After adjustment by the Cox model, three variables remained as independent predictors of the composite event: creatinine (HR, 3.93; P < 0.001), recurrent urinary tract infection (UTI) (HR, 5.05; P = 0.002), and contralateral renal length at admission (HR, 0.974; P = 0.002). The probability of the composite event at 10 years of age was estimated as 3%, 11%, and 56% for patients assigned to the low-risk, medium-risk, and high-risk groups, respectively (P < 0.001).

CONCLUSION

Our findings have shown an overall low risk of renal injury for most of infants with congenital SFK. Nevertheless, our prediction model enabled the identification of a subgroup of patients with an increased risk of renal injury over time.

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.

Evidence-based treatment of multicystic dysplastic kidney: a systematic review

OBJECTIVES

There is a lack of a standardised protocol for the investigation and non-operative management of paediatric multicystic dysplastic kidney (MCDK). Institutional protocols for non-operative management remain essentially ad hoc. The primary outcome of this systematic review is to establish the incidence of hypertension associated with an MCDK. The secondary outcome is to determine the malignancy risk associated with an MCDK. The tertiary outcome is to assess the rate of MCDK involution. Subsequent to these, an evidence-based algorithm for follow-up is described.

METHODOLOGY

A systematic review of all relevant studies published between 1968 and April 2017 was performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Studies were identified by specific inclusion and exclusion criteria, all of which included data relevant to the primary, secondary and tertiary outcomes. Hypertension was defined as systolic blood pressure greater than the 95th centile for gender, age and height centile. Subset analysis was performed for hypertension associated with an MCDK.

RESULTS

The primary outcome measure revealed a 3.2% (27/838) risk of developing hypertension associated with an MCDK. The secondary outcome measure noted a 0.07% malignancy risk (2/2820). The tertiary outcome measure established that 53.3% (1502/2820) had evidence of involution of the dysplastic kidney. A total of 44 cohort studies (2820 patients) were analysed.

CONCLUSION

Given the low risk of hypertension and malignancy, which is similar to the general population, the current conservative non-operative pathway is an appropriate management strategy. An algorithm to help support clinicians with ongoing management is proposed.

History of Childhood Kidney Disease and Risk of Adult End-Stage Renal Disease

BACKGROUND

The long-term risk associated with childhood kidney disease that had not progressed to chronic kidney disease in childhood is unclear. We aimed to estimate the risk of future end-stage renal disease (ESRD) among adolescents who had normal renal function and a history of childhood kidney disease.

METHODS

We conducted a nationwide, population-based, historical cohort study of 1,521,501 Israeli adolescents who were examined before compulsory military service in 1967 through 1997; data were linked to the Israeli ESRD registry. Kidney diseases in childhood included congenital anomalies of the kidney and urinary tract, pyelonephritis, and glomerular disease; all participants included in the primary analysis had normal renal function and no hypertension in adolescence. Cox proportional-hazards models were used to estimate the hazard ratio for ESRD associated with a history of childhood kidney disease.

RESULTS

During 30 years of follow-up, ESRD developed in 2490 persons. A history of any childhood kidney disease was associated with a hazard ratio for ESRD of 4.19 (95% confidence interval [CI], 3.52 to 4.99). The associations between each diagnosis of kidney disease in childhood (congenital anomalies of the kidney and urinary tract, pyelonephritis, and glomerular disease) and the risk of ESRD in adulthood were similar in magnitude (multivariable-adjusted hazard ratios of 5.19 [95% CI, 3.41 to 7.90], 4.03 [95% CI, 3.16 to 5.14], and 3.85 [95% CI, 2.77 to 5.36], respectively). A history of kidney disease in childhood was associated with younger age at the onset of ESRD (hazard ratio for ESRD among adults <40 years of age, 10.40 [95% CI, 7.96 to 13.59]).

CONCLUSIONS

A history of clinically evident kidney disease in childhood, even if renal function was apparently normal in adolescence, was associated with a significantly increased risk of ESRD, which suggests that kidney injury or structural abnormality in childhood has long-term consequences.

Outcomes of prenatally diagnosed solitary functioning kidney during early life

OBJECTIVE

To evaluate outcomes of congenital solitary functioning kidney (SFK) in early childhood.

STUDY DESIGN

A retrospective study of 32 children diagnosed in utero with SFK owing to unilateral renal agenesis or multicystic dysplastic kidney and followed for 1 to 11.5 years.

RESULTS

SFK length was in the compensatory hypertrophy range in 45% of fetal sonographic evaluations from mid-pregnancy, and in 85% on postnatal follow-up. Glomerular filtration rate was below normal range in 44.4%, 12.5% and 0% at <1 year, age 1 to 3 years and thereafter, respectively. Hyperfiltration was detected in 18.5% and 82.6% at <1 year and >3 years, respectively. Hypertension was documented in 35% at age 1 to 3 years but in none at an older age. Proteinuria was absent in all children.

CONCLUSION

Congenital SFK is apparently associated with little or no renal damage in infancy or childhood. Compensatory enlargement of the functioning kidney begins in utero and might serve as a prognostic indicator for normal renal function after birth.

[Solitary kidney: Management and outcome]

Solitary functioning kidneys form an important subgroup of congenital anomalies of the kidney and urinary tract (CAKUT). A solitary kidney can be congenital or acquired after unilateral nephrectomy and is often associated with ipsilateral urogenital anomalies. Both types of solitary functioning kidney are associated with an increased risk of chronic kidney disease (CKD). A low functional nephron number results in compensatory glomerular hypertension and enlargement of remnant nephrons, indicating glomerular hyperfiltration. Glomerular hyperfiltration may lead to glomerulosclerosis, which further results in hypertension, proteinuria, and decline of the glomerular filtration rate (GFR) in the long run. About 20-30% of patients with solitary functioning kidney have hypertension, proteinuria, or reduced GFR during childhood, especially those with associated CAKUT. Regular and lifetime monitoring (including growth, blood pressure, serum creatinine, proteinuria or microalbuminuria, and renal ultrasound) is required. The frequency and modality of follow-up should be adapted to individual risk for CKD. Early detection of renal injury and timely nephroprotective measures are critical.

Congenital unilateral renal agenesis: Prevalence, prenatal diagnosis, associated anomalies. Data from two birth-defect registries

BACKGROUND

The different mechanisms leading to a solitary kidney should be differentiated because the long-term outcome might be different. The fetal period is the best moment to make a true diagnosis of congenital unilateral renal agenesis (URA). The objective was to determine the prevalence of URA at birth. The secondary objectives were to describe the evolution of sensitivity of prenatal diagnosis over time and the different forms of URA (isolated and associated with other malformations) detected up to 1 year.

METHODS

The cases were retrospectively identified through two French population-based birth defect registries (Auvergne and Bas-Rhin) between 1995 and 2013. Stillbirths and fetuses up to 22 weeks of gestation and infants up to 1 year old with URA were included.

RESULTS

A total of 177 cases of URA were registered. The prevalence at birth was 4.0/10,000. The overall prenatal prevalence was 3.6/10,000 (isolated URA: 2.8/10,000). URA were isolated (59.9%), associated with isolated contralateral congenital anomaly of kidney or urinary tract (CAKUT) (7.3%) and with other extra-renal anomalies (32.8%). The total proportion of contralateral CAKUT was 15%. Only three cases presented an aneuploidy, prenatally detected and conducting to a termination of pregnancy. The sensitivity of prenatal diagnosis improved over time (from 54.2% in 1995 to 1997 to 95.8% in 2010 to 2013; p = 0.002).

CONCLUSION

Our study provides estimates of prevalence of URA at birth. A longitudinal cohort from the antenatal period to puberty should be performed to determine the prognosis of the contralateral kidney among these children with isolated, associated with contralateral CAKUT and URA with extra-renal anomalies. Birth Defects Research 109:1204-1211, 2017. © 2017 Wiley Periodicals, Inc.

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.

Long-term impact of unilateral hypo/dysplastic kidney in infants with primary vesicoureteral reflux

INTRODUCTION

Renal abnormality is not a rare finding in infants with primary VUR. The pathophysiology of the renal abnormality is considered to be congenital or acquired. Congenital hypo/dysplastic kidney is a common finding in infants with primary VUR, especially in boys. However, the long-term impact of unilateral hypo/dysplastic kidney has not been elucidated. The aim of the current study is to clarify the long-term impact of unilateral hypo/dysplastic kidney with primary vesicoureteral reflux diagnosed in infancy.

MATERIAL AND METHODS

The medical records of patients with primary VUR detected in infancy with unilateral hypo/dysplastic kidney on initial nuclear renal scan (<40% relative renal function) and no scar on the contralateral kidney were reviewed retrospectively. Among them, 29 patients who were followed for more than 5 years were included in this study. Their clinical outcomes including chronic kidney disease (CKD) stage using estimated glomerular filtration rate (GFR) and the incidences of hypertension and proteinuria were analyzed.

RESULTS

Mean age at final visit was 12.4 years (range 5.9-22.2). Estimated GFR was evaluated in 26 patients at a mean age of 12.0 years (5.9-22.2). CKD stage was 1 in all. According to the guidelines of the Japanese Society of Hypertension, while none exceeded the standard level of systolic blood pressure (BP), two patients slightly exceeded the standard level of diastolic BP. In addition, no significant proteinuria was detected in all patients, although microalbuminemia was detected in 7.7% of patients.

DISCUSSION

The prognosis of reflux nephropathy depends on the remnant renal tissue mass, that is, the number of normal nephrons. The normal congenital solitary kidney is reported to be hyperplastic with normal-sized glomeruli rather than hypertrophic ones with larger nephrons, and to have better long-term outcome regarding renal function. Accordingly, we speculated that patients with unilateral hypo/dysplastic kidney would have a similar number of nephrons to those without hypo/dysplastic kidney who have no or minimal scar as far as the contralateral kidney is well preserved. Long-term outcome of the current retrospective study was consistent with our speculation in terms of estimated GFR, proteinuria, or hypertension.

CONCLUSIONS

The present study demonstrated that significant clinical findings related to unilateral hypo/dysplastic kidney detected in infancy were rarely observed in the long term. Accordingly, unilateral hypo/dysplastic kidney seems to be a benign condition. To confirm this finding, further follow-up of these patients is necessary.

Multicystic dysplastic kidney: Impact of imaging modality selection on the initial management and prognosis

OBJECTIVE

To evaluate the impact of imaging modalities on the evaluation and prognosis of children with multicystic dysplastic kidney (MCDK) disease.

PATIENTS AND METHODS

A retrospective analysis of all children with MCDK diagnosed from 2004 until 2012 was performed. The study included 63 patients for whom all postnatal imaging modalities were available: renal bladder ultrasound (RBUS), dimercaptosuccinic acid scan (DMSA) and voiding cystourethrogram (VCUG). Cases with major congenital abnormalities or incomplete data were excluded. Abnormalities in the contralateral kidney and the fate of MCDK were also addressed.

RESULTS

At diagnosis, the average age was four-and-a-half months. The majority of cases were detected antenatally (87%). Postnatal RBUS and DMSA scans established the diagnosis of MCDK in 92% and 98% of patients, respectively. DMSA showed photopenic areas in the contralateral kidneys in 10% of patients; all of them had hydronephrosis and were confirmed to have vesicoureteral reflux (VUR). Contralateral VUR was detected in 16 patients; 63% of them had hydronephrosis. After a mean follow-up of three-and-a-half years, involution occurred in 62% of patients and the involution rate was inversely proportional to the initial size.

CONCLUSIONS

The classical appearance of MCDK on RBUS was sufficient to establish the diagnosis in most patients. DMSA scan was more accurate in confirming the diagnosis and evaluating the contralateral kidney. Selective screening for VUR in patients with contralateral hydronephrotic kidney should be considered.

Clinical implications of the solitary functioning kidney

Congenital anomalies of the kidney and urinary tract are the major cause of ESRD in childhood. Children with a solitary functioning kidney form an important subgroup of congenital anomalies of the kidney and urinary tract patients, and a significant fraction of these children is at risk for progression to CKD. However, challenges remain in distinguishing patients with a high risk for disease progression from those patients without a high risk of disease progression. Although it is hypothesized that glomerular hyperfiltration in the lowered number of nephrons underlies the impaired renal prognosis in the solitary functioning kidney, the high proportion of ipsilateral congenital anomalies of the kidney and urinary tract in these patients may further influence clinical outcome. Pathogenic genetic and environmental factors in renal development have increasingly been identified and may play a crucial role in establishing a correct diagnosis and prognosis for these patients. With fetal ultrasound now enabling prenatal identification of individuals with a solitary functioning kidney, an early evaluation of risk factors for renal injury would allow for differentiation between patients with and without an increased risk for CKD. This review describes the underlying causes and consequences of the solitary functioning kidney from childhood together with its clinical implications. Finally, guidelines for follow-up of solitary functioning kidney patients are recommended.

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.

Excessive urinary tract dilatation and proteinuria in pregnancy: a common and overlooked association?

BACKGROUND

Proteinuria and dilatation of the urinary tract are both relatively common in pregnancy, the latter with a spectrum of symptoms, from none to severe pain and infection. Proteinuria is a rare occurrence in acute obstructive nephropathy; it has been reported in pregnancy, where it may pose a challenging differential diagnosis with pre-eclampsia.The aim of the present study is to report on the incidence of proteinuria (≥ 0.3; ≥ 0.5 g/day) in association with symptomatic-severe urinary tract dilatation in pregnancy.

METHODS

Case series.

SETTING

Nephrological-Obstetric Unit dedicated to pregnancy and kidney diseases (January 2000-April 2011).

SOURCE

database prospectively updated since the start of the Unit. Retrospective review of clinical charts identified as relevant on the database, by a nephrologist and an obstetrician.

RESULTS

From January 2000 to April 2011, 262 pregnancies were referred. Urinary tract dilatation with or without infection was the main cause of referral in 26 cases (predominantly monolateral in 19 cases): 23 singletons, 1 lost to follow-up, 1 twin and 1 triplet. Patients were referred for urinary tract infection (15 cases) and/or renal pain (10 cases); 6 patients were treated by urologic interventions ("JJ" stenting). Among them, 11 singletons and 1 triple pregnancy developed proteinuria ≥ 0.3 g/day (46.1%). Proteinuria was ≥ 0.5 g/day in 6 singletons (23.1%). Proteinuria resolved after delivery in all cases. No patient developed hypertension; in none was an alternative cause of proteinuria evident. No significant demographic difference was observed in patients with renal dilatation who developed proteinuria versus those who did not. An association with the presence of "JJ" stenting was present (5/6 cases with proteinuria ≥ 0.5 g/day), which may reflect both severer obstruction and a role for vescico-ureteral reflux, induced by the stent.

CONCLUSIONS

Symptomatic urinary tract dilatation may be associated with proteinuria in pregnancy. This association should be kept in mind in the differential diagnosis with other causes of proteinuria in pregnancy, including pre-eclampsia.

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.

Unilateral multicystic dysplastic kidney: does initial size matter?

BACKGROUND

We report the long-term follow-up of children with antenatally detected unilateral multicystic dysplastic kidney (MCDK) who were followed between 1985 and 2009.

METHODS

Involution rates were documented over time based on the initial size of the MCDK, as documented on postnatal ultrasound (USS), as well as long-term complications and renal function.

RESULTS

In 323 patients (182 male), 10 % of MCDK had involuted, as evidenced on the first postnatal USS, with survival function analysis showing the probability of complete involution to be 35 % in 249 patients by 2 years of age, 47 % in 180 patients by 5 years of age and 62 % in 94 patients by 10 years of age. There was a significant difference in the involution rates of MCKD at the 10-year follow-up between MCDK with an initial size of >5 cm versus MCDK with an initial size of ≤5 cm (p < 0.0001). No patients in the whole cohort developed sustained hypertension or malignancy during a median follow-up of 10.1 years (range 0.3-15.4 years). Median estimated glomerular filtration rate (eGFR) in 76 patients (7 at 5 years, 69 at 10 years) was 93 ml/min/1.73 m(2) (range 46-175 ml/min/1.73 m(2)), with 40 (53%) having an eGFR of between 90 and 140 ml/min/1.73 m(2). Twenty-three (30 %) of the 76 patients at 10 years had normal eGFR (90-140 ml/min/1.73 m(2)) as well as complete involution of the MCDK, compensatory hypertrophy of the contralateral kidney, no proteinuria and no hypertension.

CONCLUSIONS

Larger MCDK at birth are less likely to involute during the first decade of life. However, conservative management remains justified due to the lack of complications. A minority of patients fulfil current criteria for discharge from specialty follow-up at 10 years.

Abdominopelvic ultrasound: a cost-effective way to diagnose solitary kidney

PURPOSE

Solitary kidneys are detected on approximately 1 of 1,500 prenatal ultrasounds and during evaluation for other urological complaints. Although renal scintigraphy is currently the gold standard for confirming the diagnosis and ruling out renal ectopia, scintigraphy is associated with radiation exposure, placement of an intravenous line and sedation. We hypothesize that ultrasonography alone is sufficient to detect solitary kidneys and that confirmatory renal scintigraphy is unnecessary.

MATERIALS AND METHODS

We reviewed the records of children with a solitary kidney who underwent ultrasound and nuclear scintigraphy at our institution from 2001 to 2010. Radiological findings were compared to assess the accuracy of ultrasound in diagnosing solitary kidneys. Costs were calculated based on 2011 Medicare global reimbursement.

RESULTS

A total of 25 children met the inclusion criteria of undergoing ultrasound and renal scintigraphy (dimercapto-succinic acid or mercaptoacetyltriglycine scan). The majority of cases were male (16, 64%) and left sided (17, 68%). Median age was 9 days (range 1 day to 11.6 years) at first ultrasound and 4.4 months (3 weeks to 12 years) at first renal scintigraphy. In 24 patients ultrasound correctly diagnosed a solitary kidney as confirmed by nuclear scan. In 1 patient ultrasound suggested a pelvic kidney but repeat ultrasound was negative, as was dimercapto-succinic acid scan. The diagnostic accuracy of ultrasound was 96%. Medicare reimbursement for dimercapto-succinic acid scan (CPT 78700) is $460 to $720 ($222 plus $240 for radiotracer plus $260 for anesthesia, if used).

CONCLUSIONS

Our findings suggest that ultrasonography alone is sufficient to make the diagnosis of solitary kidney. Omitting routine renal scintigraphy saves approximately $460 to $720 per case, and avoids radiation and discomfort without sacrificing diagnostic accuracy.

The Clinical Research Office of the Endourological Society Percutaneous Nephrolithotomy Global Study: nephrolithotomy in 189 patients with solitary kidneys

BACKGROUND AND PURPOSE

The study compared characteristics and outcomes in patients with solitary and bilateral kidneys who were treated with percutaneous nephrolithotomy (PCNL) in the Clinical Research Office of the Endourological Society (CROES) PCNL Global Study.

PATIENTS AND METHODS

Data from consecutively treated patients from 96 centers worldwide were collated after a 1-year period. The following variables in patients undergoing PCNL with solitary or bilateral kidneys were compared: Prevalence, patient characteristics, intraoperative differences and outcomes, including bleeding and transfusion rates, renal function, and stone-free rates.

RESULTS

Data from 5803 patients were collated; 189 (3.3%) with solitary and 5556 (96.7%) with bilateral kidneys. Patient characteristics were well matched generally with the exception of cardiovascular disease and American Society of Anesthesiologists (ASA) risk scores, which were significantly greater in patients with solitary than with bilateral kidneys (P<0.0001 and P=0.004, respectively). Patients with solitary kidneys had also undergone significantly more procedures to remove calculi before this survey than bilateral patients (P= 00.049 -<0.0001). Levels of renal impairment were significantly greater (P<0.0001) and stone-free rates were significantly lower (P=0.001) post-PCNL in solitary than bilateral kidney patients. Although bleeding rates were the same in both groups, transfusion rates were significantly greater in solitary kidney patients (P=0.014).

CONCLUSIONS

Patients with a solitary kidney had a higher cardiovascular risk and ASA score. Outcomes related to morbidity and stone-free rate were less favorable for solitary kidneys.

Long-term risk of chronic kidney disease in unilateral multicystic dysplastic kidney

The clinical spectrum of renal dysplasia includes the non-functioning multicystic dysplastic kidney (MCDK). We report our experience of the outcome of unilateral MCDK and its contralateral kidney in 101 children with the diagnosis of MCDK from 1985 to 2009. Data collected included urine protein/creatinine ratio, estimated GFR (eGFR), blood pressure, surgical intervention, renal length and abnormalities of the contralateral kidney, and the involution rate. There was a predominance of left-sided MCDK. Diagnosis was made prenatally in 86.7%. Contralateral abnormalities included vesicoureteral reflux (16.8%), UPJ obstruction (4.1%), and megaureter (2.4%). Complete involution of MCDK occurred within 5 years in 60%. Compensatory hypertrophy of the contralateral kidney to >97% occurred in 74.1%. Nephrectomy was performed in 19.8%. There was an increased risk of chronic kidney disease (CKD) stage ≥ 2, and hypertension in those with contralateral abnormalities (p<0.0001; p<0.001 respectively). In those without contralateral abnormalities, hyperfiltration with mean eGFR of 149 ± 13 ml/min/1.73 m(2) was seen in 32% and proteinuria in 9.8%. There was a significantly inverse relationship between proteinuria and eGFR (p<0.0001). In conclusion, children with contralateral abnormalities are at risk for developing decreased kidney function, whereas a substantial number of patients with no obvious contralateral abnormalities have markers of renal injury. Therefore, systematic follow-up of all patients is recommended.

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.

Postnatal evaluation of infants with an abnormal antenatal renal sonogram

PURPOSE OF REVIEW

Antenatally detected renal abnormalities are frequently encountered. Recommended postnatal evaluation of these infants has evolved to minimize invasive testing while maximizing detection of significant abnormalities.

RECENT FINDINGS

There is a low rate of detectable renal abnormalities in infants with a normal postnatal sonogram at 4-6 weeks of age. Routine prophylactic antibiotics are not indicated in infants with isolated antenatal hydronephrosis. Infants with a multicystic dysplastic kidney and a normal contralateral kidney on renal ultrasound do not require further evaluation. Parents of these children should be counseled on symptoms of urinary tract infections to allow prompt diagnosis.

SUMMARY

All infants with abnormalities on antenatal sonogram should undergo postnatal evaluation with a sonogram after birth and at 4-6 weeks of age. Further evaluation can be safely limited when the postnatal sonogram is normal at 6 weeks of age.

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.

Management and etiology of the unilateral multicystic dysplastic kidney: a review

In children, unilateral multicystic dysplastic kidney (MCDK) is one of the most frequently identified urinary tract abnormalities. A variety of proposed etiologies has been associated with the underlying pathogenesis of MCDK. These include genetic disturbances, teratogens, in utero infections, and urinary outflow tract obstruction. From 5-43% of the time, MCDK has associated genito-urinary anomalies, both structural and functional in nature. A review of the literature reveals that involution rates are reported to be 19-73%, compensatory hypertrophy of the contralateral kidney occurs from 24-81% of the time, and estimated glomerular filtration rates (GFRs) (by the Schwartz formula) range from 86-122 ml/min per 1.73 m(2) body surface area. Most authors suggest serial ultrasonography to monitor contralateral growth, routine blood pressure monitoring, and a serum creatinine monitoring algorithm. The risk of hypertension in those with MCDKs does not appear to be greater than that of the general population, and the rates of malignant transformation of MCDK are small, if at all increased, in comparison with those in the general population. If the patient develops a urinary tract infection or has abnormalities of the contralateral kidney, shown on ultrasound, a voiding cystourethrogram is recommended. Finally, the body of literature does not support the routine surgical removal of MCDKs.

Unilateral multicystic dysplastic kidney: a meta-analysis of observational studies on the incidence, associated urinary tract malformations and the contralateral kidney

BACKGROUND

Many papers are published on cohorts with unilateral multicystic dysplastic kidney (MCDK) patients, but show variable results as to the incidence of associated urinary tract abnormalities. The objective of this study was to describe the status of the urinary tract, including contralateral hypertrophy and malformations, in patients with unilateral MCDK based on a meta-analysis of the literature, taking into account the timing of diagnosis (pre- versus postnatal) as a possible source of bias.

METHODS

A systematic review of the scientific literature in English was conducted using PubMed and Embase. A meta-analysis was performed with the studies that were identified using our reproducible search.

RESULTS

Based on analysis of the data in 19 populations, the overall incidence of unilateral MCDK is 1 in 4300 with an increasing trend over the years. A total of 67 cohorts with over 3500 patients with unilateral MCDK were included in the meta-analysis. Fifty-nine percent of patients were male and the MCDKs were significantly more often found on the left side (53.1%). Associated anomalies in the solitary functioning kidney were found in 1 in 3 patients, mainly vesicoureteric reflux (VUR, in 19.7%). In patients with VUR, 40% have severe contralateral VUR, defined as grade III-V. Contralateral hypertrophy, present in 77% of patients after a follow-up of at least 10 years, showed a trend to be less pronounced in patients with VUR. Timing of the diagnosis of MCDK did not essentially influence the results.

CONCLUSIONS

These aggregate results provide insight into the incidence, demographic data and associated anomalies in patients with unilateral MCDK. One in three patients with unilateral MCDK show anomalies in the contralateral, solitary functioning kidney. However, studies into the long-term consequences of these anomalies are scarce.