Cumulative risk to develop hypertension: on the left office blood pressure values; on the right measurements with ABPM. Group A1: multicystic dysplastic kidney involuted within 4 years of age; group A2: multicystic dysplastic kidney persistent beyond 4 years of age; group B: nephrectomies for multicystic dysplastic kidney; group C: kidney agenesis

Cumulative risk to develop hypertension: on the left office blood pressure values; on the right measurements with ABPM. Group A1: multicystic dysplastic kidney involuted within 4 years of age; group A2: multicystic dysplastic kidney persistent beyond 4 years of age; group B: nephrectomies for multicystic dysplastic kidney; group C: kidney agenesis

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Purpose Solitary functioning kidney (SFK) may be associated to hypertrophy, hypertension and chronic kidney disease. We evaluated blood pressure (BP) of children with congenital SFK comparing agenesis to multicystic dysplastic kidney (MCDK) and correlated BP profiles with renal dimensions of affected and contralateral kidney. Methods We compared 4...

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... At present, nomograms constructed from US measurements to assess kidney length in children with two kidneys [24][25][26] are used. Compensatory enlargement of the CSK in children is defined either in relation to age (length ≥ 2 or >2.5 SD) [23,[27][28][29][30][31][32][33], or in relation to height (≥ 95th percentile) [7,17,22,[34][35][36][37], while in adults, the expected value is ≥ 120 mm [38,39]. As there is a wide variability of physical growth with age, we believe that relating kidney length to height rather than to age is more appropriate. ...
... Ten studies evaluated BP by ABPM in a total number of 379 children with CSK [28,32,37,[70][71][72][73][74][75]85] (Table 7). Five studies reported data on kidney length for a total of 136 patients and about 86% presented compensatory enlargement [28,32,70,72,85]. ...
... Ten studies evaluated BP by ABPM in a total number of 379 children with CSK [28,32,37,[70][71][72][73][74][75]85] (Table 7). Five studies reported data on kidney length for a total of 136 patients and about 86% presented compensatory enlargement [28,32,70,72,85]. Six studies reported data on ipsilateral CAKUT, which were present in a minority of patients [28,37,70,71,75,85], while in the study by Lubrano et al., 24 out of 38 had kidney scars [74]. ...
Article
Background: 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.
... Normally, poor renal outcomes associated with SFK are attributed to glomerular alterations, secondary to hyperfiltration-mediated injury [27,44,45]. It is considered that albuminuria and hypertension are reliable markers of this process [21,46,62]. Patients who already have proteinuria and hypertension may be at increased risk of developing complications [49]. ...
... There is no specific treatment for congenital SFK. The management is conservative if complications are absent [62]. The purpose of monitoring these patients is to identify risk factors and complications as soon as they appear and intervene quickly. ...
Article
Background: Solitary functioning kidney (SFK) is a subgroup of the Congenital Anomalies of the Kidneys and Urinary Tract (CAKUT). Although in the past the prognosis of these patients was considered good, numerous studies have shown different levels of kidney damage associated with this condition. Serum creatinine measurement is still the most used marker to assess renal function, even though the limitations are widely known. Objective: The present review aimed to summarize and update the scientific literature on congenital SFK, discussing its pathophysiology, diagnosis, complications, prognosis, role of novel urinary biomarkers, treatment and follow-up. Results: The natural history of congenital SFK is still an unresolved issue due to several factors. Although it has not yet been proven in humans, Brenner's hyperfiltration hypothesis is the most concrete theory to explain the poor renal outcomes of patients born with one functioning kidney. The search for novel urinary biomarkers capable of assessing renal function and predicting renal outcomes has already started, but there are still few studies with this specific population. Among the most studied markers, Cystatin C, EGF and NGAL have shown potential usefulness for the follow-up of these patients. The treatment still relies on the search for kidney injury and general renoprotective measures. Conclusion: Further research with longer follow-up duration is needed to better understand the natural course of congenital SFK and the role of novel urinary biomarkers in this specific population. Thus, it will be possible to improve the prognosis of these patients.
... ABPM revealed the absence of dipping in diastolic and/or systolic BP in 82% of the patients with SFK. 24 In children with congenital solitary kidney, an inverse correlation between the renal size of the remnant kidney and mean ABPM has been found. 25 This finding reinforces the knowledge that reduced nephron mass is associated with elevated BP in adulthood, as suggested in research. ...
... Adequate length of the congenital solitary functioning kidney is a key parameter for renal function [12]. However, according to several theories and some evidence of remained functional renal tissue in MCDK [13], the renal growth slope can be different between renal A c c e p t e d A r t i c l e agenesis and MCDK [14]. ...
Article
Purpose: This study aimed to analyze the renal growth slope in children with congenital and acquired solitary functioning kidneys. Methods: This retrospective study included all renal ultrasonography examinations performed in children in the agenesis, multicystic dysplastic kidney (MCDK), or nephrectomy group between September 2002 and February 2019. We reviewed the images and recorded the contralateral kidney size only when there was no focal lesion. Linear mixed model or piecewise linear mixed model analyses with a time point of 24 months of age were performed. Results: There were 132 patients, including 26 patients in the agenesis group, 35 in the MCDK group, and 71 in the nephrectomy group. The nephrectomy group showed the largest baseline kidney size (7.4 cm vs. 5.3 cm in the agenesis group [P<0.001] and 5.2 cm in the MCDK group [P<0.001]) and the smallest overall growth slope (0.04 cm/mo vs. 0.06 cm/mo in the agenesis group [P=0.004] and 0.07 cm/mo in the MCDK group [P<0.001]). However, considering the time point of 24 months for reaching adult renal function, there were significant changes in slope, from 0.1 cm/mo before 24 months of age to 0.03 cm/mo after 24 months of age in all three groups (P<0.001), without a significant difference among the groups. Conclusion: Significant changes were found in the renal growth slope before and after 24 months of age, with no significant difference between congenital and acquired solitary functioning kidneys.
... It is well established that following a reduction in kidney mass whether it is congenital in origin or following unilateral nephrectomy in the child or the adult, there is marked compensatory kidney growth that is comprised of hypertrophy of both the kidney tubules and the glomerulus (Moritz et al., , 2005Singh et al., 2010;Fong et al., 2014;Chen et al., 2016;Wang et al., 2019;Zambaiti et al., 2019). In humans, compensatory kidney hypertrophy of the SFK begins as early as 20 weeks into gestation and by 36 weeks into gestation there is an ∼11% mean enlargement of the SFK compared with age matched controls (Van Vuuren et al., 2012b). ...
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Children born with a solitary functioning kidney (SFK) have an increased risk of hypertension and kidney disease from early in adulthood. In response to a reduction in kidney mass, the remaining kidney undergoes compensatory kidney growth. This is associated with both an increase in size of the kidney tubules and the glomeruli and an increase in single nephron glomerular filtration rate (SNGFR). The compensatory hypertrophy and increase in filtration at the level of the individual nephron results in normalization of total glomerular filtration rate (GFR). However, over time these same compensatory mechanisms may contribute to kidney injury and hypertension. Indeed, approximately 50% of children born with a SFK develop hypertension by the age of 18 and 20–40% require dialysis by the age of 30. The mechanisms that result in kidney injury are only partly understood, and early biomarkers that distinguish those at an elevated risk of kidney injury are needed. This review will outline the compensatory adaptations to a SFK, and outline how these adaptations may contribute to kidney injury and hypertension later in life. These will be based largely on the mechanisms we have identified from our studies in an ovine model of SFK, that implicate the renal nitric oxide system, the renin angiotensin system and the renal nerves to kidney disease and hypertension associated with SFK. This discussion will also evaluate current, and speculate on next generation, prognostic factors that may predict those children at a higher risk of future kidney disease and hypertension.
Article
Use of ambulatory blood pressure monitoring in children and adolescents has markedly increased since publication of the last American Heart Association scientific statement on pediatric ambulatory blood pressure monitoring in 2014. In addition, there has also been significant expansion of the evidence base for use of ambulatory blood pressure monitoring in the pediatric population, including new data linking ambulatory blood pressure levels with the development of blood pressure–related target organ damage. Last, additional data have recently been published that enable simplification of the classification of pediatric ambulatory monitoring studies. This scientific statement presents a succinct review of this new evidence, guidance on optimal application of ambulatory blood pressure monitoring in the clinical setting, and an updated classification scheme for the interpretation of ambulatory blood pressure monitoring in children and adolescents. We also highlight areas of uncertainty where additional research is needed.
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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/1.73m²/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.
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Context A congenital solitary functioning kidney (cSFK) is a common developmental defect that predisposes to hypertension and chronic kidney disease (CKD) as a consequence of hyperfiltration. Every urologist takes care of patients with a cSFK, since some will need lifelong urological care or will come with clinical problems or questions to an adult urologist later in life. Objective We aim to provide clear recommendations for the initial clinical management and follow-up of children with a cSFK. Evidence acquisition PubMed and EMBASE were searched to identify relevant publications, which were combined with guidelines on related topics and expert opinion. Evidence synthesis Initially, cSFK diagnosis should be confirmed and risk factors for kidney injury should be identified using ultrasound. Although more research into early predictors of kidney injury is needed, additional congenital anomalies of the kidney or urinary tract and absence of compensatory kidney hypertrophy have repeatedly been associated with a worse prognosis. The role of voiding cystourethrography and antibiotic prophylaxis remains controversial, and is complicated by the exclusion of children with a cSFK from studies. A yearly follow-up for signs of kidney injury is recommended for children with a cSFK. As masked hypertension is prevalent, annual ambulatory blood pressure measurement should be considered. During puberty, an increasing incidence of kidney injury is seen, indicating that long-term follow-up is necessary. If signs of kidney injury are present, angiotensin converting enzyme inhibitors are the first-line drugs of choice. Conclusions This overview points to the urological and medical clinical aspects and long-term care guidance for children with a cSFK, who are at risk of hypertension and CKD. Monitoring for signs of kidney injury is therefore recommended throughout life. Large, prospective studies with long-term follow-up of clearly defined cohorts are still needed to facilitate more risk-based and individualized clinical management. Patient summary Many children are born with only one functioning kidney, which could lead to kidney injury later in life. Therefore, a kidney ultrasound is made soon after birth, and other investigations may be needed as well. Urologists taking care of patients with a solitary functioning kidney should realize the long-term clinical aspects, which might need medical management.