Congenital Solitary Kidney from Birth to Adulthood

Purpose: To evaluate the course of prenatally diagnosed and early-enrolled congenital solitary functioning kidney (CSFK) patients followed-up until adulthood and to identify risk factors for kidney injury. Material and Methods: Among all CSFK patients followed-up (period: 1993–2018), we recalled 56 patients with prenatal diagnosis and CSFK confirmation at 1-3 months of life reaching at least 18 years of age. Serum uric acid (SUA), heavy smoking (≥25 cigarettes/day) and overweight/obesity were clustered as modifiable risk factors (MRF). Kidney injury was defined by estimated glomerular filtration rate (eGFR) <90 ml/min/1.73m2 and/or 24h-ambulatory blood pressure monitoring confirmed hypertension and/or proteinuria. MRF and Congenital Anomalies of the Kidney and Urinary Tract (CAKUT) of CSFK were evaluated as risk factors for kidney injury. Results: The mean follow-up period was 21.1 years (range: 18-33 years). Mild kidney injury was found in 15 out of 56 patients (26.8%). The mean age at proteinuria, reduced eGFR and hypertension onset was 19.7 years (1.2 SDS), 20.7 years (2.7 SDS), and 22 years (5.6 SDS), respectively. Patients with CAKUT of CSFK and with both CAKUT of CSFK and MRF presented survival free from kidney injury of 0% at 22.2 and 24.2 years of age, respectively. Patients with MRF presented survival of 42.4% at 30 years. Patients without CAKUT of CSFK nor MRF presented 100% of survival at 30 years of age (p=0.002). The presence of CAKUT of CSFK was the only significant risk factor (Hazard Ratio=4.9; 95% Confidence Interval: 1.8–14.2; p=0.003). Conclusions: The outcomes of CSFK in early adulthood appear better than previously reported. Prompt diagnosis of CAKUT, healthy life-style promotion and monitoring of SUA may improve the prognosis of CSFK patients.