[Solitary kidney: Management and outcome]

Solitary functioning kidneys form an important subgroup of congenital anomalies of the kidney and urinary tract (CAKUT). A solitary kidney can be congenital or acquired after unilateral nephrectomy and is often associated with ipsilateral urogenital anomalies. Both types of solitary functioning kidney are associated with an increased risk of chronic kidney disease (CKD). A low functional nephron number results in compensatory glomerular hypertension and enlargement of remnant nephrons, indicating glomerular hyperfiltration. Glomerular hyperfiltration may lead to glomerulosclerosis, which further results in hypertension, proteinuria, and decline of the glomerular filtration rate (GFR) in the long run. About 20-30% of patients with solitary functioning kidney have hypertension, proteinuria, or reduced GFR during childhood, especially those with associated CAKUT. Regular and lifetime monitoring (including growth, blood pressure, serum creatinine, proteinuria or microalbuminuria, and renal ultrasound) is required. The frequency and modality of follow-up should be adapted to individual risk for CKD. Early detection of renal injury and timely nephroprotective measures are critical.