Congenital Solitary Kidney in Children: Size Matters

Abstract

Some children with congenital solitary kidney show decreased glomerular filtration rate. Associated anomalies of the kidney/urinary tract and insufficient renal length appear to be significant risk factors. Adequate length of the congenital solitary kidney is a key parameter for maintenance of renal function and should be examined routinely during followup.

Genetics of Congenital Anomalies of the Kidney and Urinary Tract: The Current State of Play

“…In a cohort of 312 children affected by renal malformations (excluding cases with isolated ureteric anomalies) who were followed up until the age of 30 years, an overall poor renal survival for CAKUT patients was described, with a lower outcome for patients carrying bilateral renal hypodysplasia, solitary kidney, and posterior urethral valves, compared with other categories [9]. Nevertheless, retrospective data from an Italian cohort of 146 children 0–18 years old with congenital solitary kidney show a decreased estimated glomerular filtration rate in 12% of the population at a median age of 2.2 years, an estimated survival of 82% at 10 years and proteinuria and/or systemic hypertension in less than 5% of the population; these data highlight the importance in renal outcome of an adequate size of the solitary kidney, which, if smaller than expected, can significantly increase the risk of chronic kidney disease (CKD) [10]. Anyhow, children with CAKUT are known to experience a slower progression of CKD compared to those with glomerular disease [11].…”

Risk stratification for children with a solitary functioning kidney

“…Patient characteristics such as sex and ethnicity could be involved. Most studies showed no association between sex and risk for kidney injury in SFK patients [4,6,[8][9][10][11][12]. One notable exception is the study by Alfandary et al in which male adolescents with SFK had a threefold higher risk of kidney injury compared to female patients [11].…”

“…In a normal cSFK, compensatory growth is expected to start before birth and continue throughout childhood [12,21,44,45]. Before birth, this growth can comprise both hyperplasia (increase in cell number) and hypertrophy (increase in cell size) [46].…”

“…The evidence that the absence of compensatory growth is associated with the risk of kidney injury is convincing. Several studies have found that larger SFK size, especially when present at birth, was associated with a lower risk of kidney injury [4,6,11,12,17,21,22] suggesting that a responsive mechanism triggering hyperplasia is very important in dealing with kidney mass reduction. The evidence supporting an association between additional CAKUT of the SFK and kidney injury is also strong, with hazard ratios varying between 1.7 and 13, which is in line with the results reported by Dr. Matsell and colleagues [4-6, 11, 12, 17, 20, 23-26].…”

Born with a solitary kidney: at risk of hypertension

“…During the seventies, studies on animals w i t h e x t e n s i v e r e n a l a b l a t i o n d e m o n s t r a t e d glomerulosclerosis with progressive azotemia, proteinuria, and hypertension [1]. Since then, the association between a low number of nephrons and blood pressure dysregulation or hypertension has also been described in humans, in particular in subjects with a solitary kidney [2][3][4][5][6][7][8][9][10][11].…”