Abstract
We aimed to evaluate the prognostic value of renal length (RL) > 2 standard deviation scores (SDS) measured by renal ultrasound (RUS), across infancy, childhood and adolescence, in identifying which patients with congenital solitary functioning kidney (CSFK) are at lower risk of developing kidney injury (KI). We also estimated the cost saving of integrating the current follow-up protocols with an early RUS algorithm (ERUSA). Fifty-six CSFK adult patients who were 1–3 months old at first observation of undergoing RUS were enrolled. KI was defined by hypertension and/or proteinuria and/or declined renal function. ERUSA was assessed by early (at 1–3 months of life) RUS and was retrospectively tested in our patients. ERUSA establishes that patients with RL > 2SDS at early RUS do not undergo further follow-ups. The others undergo another RUS at 1 year of age along with follow-ups according with current protocols, with the exception of RUS which could be no longer performed. Direct and indirect costs were calculated for each analysed protocol and the cost saving of applying ERUSA was calculated. None of the patients with early RL > 2SDS presented KI in adulthood. A RL > 2SDS was predictive of absence of KI only at 1–3 months (OR = infinity) and 1 year of age (OR = 0.13; 95%CI: 0.03–0.66; p = 0.01). ERUSA provided a total cost-sparing ranging from 38.6% to 55.3% among the analysed follow-up protocols. With ERUSA, no patients developing KI in adulthood were missed. In conclusion, only a RL > 2SDS at 1–3 months and 1 year of age predicted good prognosis in young adulthood. ERUSA can guide a cost-sparing follow-up strategy in CSFK patients while maintaining important long-term information.
Highlights
As further confirmation of the prognostic relevance of a renal length (RL) > 2SDS in congenital solitary functioning kidney (CSFK) patients, we previously found that a RL > 2SDS in the neonatal period could allow the identification of patients at lower risk of both presenting with vesico-ureteral reflux, itself associated with development of negative outcomes in CSFK patients [3], and future decline of estimated glomerular filtration rate [4]
The latter, in turn, are different from CSFKs never reaching RL > 2SDS. The difference among these three groups could be the nephronic endowment, which is highest, and fully attained prenatally, for patients born with RL > 2SDS, intermediate for patients reaching RL > 2SDS later in life, and lowest for patients never reaching RL > 2SDS [4]. This could have an impact on the risk of hyperfiltration and kidney injury (KI) which is highest for patients never reaching RL > 2SDS and lowest for patients born with RL > 2SDS
A RL > 2SDS at 1–3 months of life identifies the population of CSFK patients with the best prognosis, and at 1 year of age it selects patients with reduced risk of KI
Summary
A RL > 2SDS in the early post-natal period could reflect renal hyperplasia characterized by increased nephron endowment [5–7] and subsequent reduced risk of hyperfiltration and kidney injury (KI) [8]. Most CSFK patients, develop renal compensatory hypertrophy (RL > 2SDS) within the first years of life [9]. We evaluated the utility of RL > 2SDS, periodically measured across infancy, childhood and adolescence, in selecting patients at lower risk of developing KI in adulthood (primary outcome). To identify earlyin-life predictors of absence of KI in adulthood could be useful in personalizing follow-up protocols of CSFK children in order to reduce unnecessary medicalization with impact on stressful procedures (such as blood sample collection in children) and economic costs. We estimated the cost saving of integrating the current follow-up protocols [2,10] with the early RUS algorithm (ERUSA) (secondary outcome). The ERUSA is based on the hypothesis that early RUS could provide the instruments to personalize follow-up
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