Immunohistochemical Expression Pattern of RIP5, FGFR1, and FGFR2 in Normal Human Kidney Development and Congenital Anomalies of the Kidney and Urinary Tract (CAKUT)

Background: In the last decade the association between congenital single functional kidney (cSFK) and increased risk of hypertension, proteinuria and kidney injury has become clear. Regarding CKD long-term outcome, kidney hypertrophy at ultrasound (US) in the early months of life is reported as protective. Kidney US measuring renal lenght (BPL) and renal scintigraphy (RS) measuring GFR (mGFR) are both useful tools for the clinical management. The follow-up is frequently based on local protocols, although clinical recommendations have been proposed recently. The aim of the present study was to assess the utility of RS and to compare it to US in gathering information on kidney function, long term outcome and the appropriate use in the follow-up of patients with cSFK. Methods: Retrospective, monocentric, observational study enrolling pediatric cSKF patients. Demographic, clinical, instrumental and laboratory data were collected from medical records for all the patients included in this study. CKD was considered as composite outcome (at least one: reduced mGFR or eGFR, proteinuria in at least two different examinations, hypertension). Results: 163 cSFK patients were included. The BPL showed a linear increase over time, with curve flattening after 144 months of age. Conversely, mGFR rapidly increased between 0 and 60 months, stabilizing thereafter (Fig.1) and reaching a median value over the threshold of normal function between 24 and 60 months; we observed a slight decrease after 180 months, although not statistically significant. Comparing the trend of BPL and mGFR over time, we observed a significant correlation (R2=0.5, p-value<0.05) between 1 and 60 months of life, that was lot thereafter. Proteinuria, hypertension, impaired eGFR and mGFR were found in 11.7 %, 18.7%, 30.4% and 39.3% patients, respectively, with overall CKD rate of 41.6%. Of note, 25% of these patients were identified only by RS, having no other considered abnormality. Moreover in this subgroup patients only one showed kidney hypertrophy at US before the age of 60 months. Conclusions: RS can be as useful as US in the follow-up of cSFK. It allows to early spot an higher number of CKD patients and probably represent the best option for those with late referral in which early US is not available, to guide the clinicians in defining the risk of CKD and inform prognosis.