Is the Prognosis of Single Functional Kidney (SFK) Benign? A Population-based Study

Purpose: The outcome of congenital single functioning kidney (SFK) is of extensive debate. We conducted a large -scale population-based study to investigate an early renal injury in adolescents with SFK.

Material and methods: We accessed data from the compulsory medical evaluation of 17 years old in Israel, prior to their enlistment for military service between 2006-2018. The incidence of congenital SFK and the occurrence of renal injury, including proteinuria, hypertension, and decreased eGFR were documented.

Results: Of 979,630 candidates, 353 were diagnosed with SFK. The incidence of congenital SFK since 1995 was~1\1800 births with male to female ratio of 2.7:1. 42.2% of participants with SFK had renal injury by the age of 17 compared to 9.4% in the control group (P<0.001). Hypertension was reported in 31.7% of the SFK group compared to 9.1% in the control group (P<0.001). Proteinuria and eGFR below 90ml/min/1.73m2 were reported in 18.2% and 11.5% of the SFK group compared to 0.4% and 0.05% in the control group (p<0.0001). Morbid obesity was reported in 7.2% of SFK compared to 0.8% in the control group (p<0.0001). In a multivariate analysis, male gender ,SFK and higher BMI were found to be significantly associated with for renal injury.

Conclusion: this large population-based study documents a significant risk for renal injury among adolescent with SFK at the age of 17 years old. Obesity is more frequent among SFK and represents a major risk factor for renal injury, possibly warranting closer follow-up in this group of patients