Aims: To explore the clinical course of children with 'single kidney' (defined as either solitary or single functioning kidney) with reference to renal function (GFR and proteinuria), body height and particularly sonomorphological features.
Patients and methods: In this retrospective monocentric study we evaluated 119 children with solitary or single functioning kidney (over 90% unilateral function on isotope scan) between 1997 and 2007. Patients were followed for 6.3 years (median, range 1-17) and had at least 3 renal ultrasound examinations (median 8).
During recruitment six children were identified with chronic kidney disease (CKD) stage III or worse. These patients were analysed separately.
Results: Etiology of 'single kidney' was attributed to contralateral multicystic dysplastic kidney (26%), tumornephrectomy (24%), renal agenesis (18%), hypo-/dysplasia (11%) and obstructive or refluxive uropathy (18%). Irrespectively of etiology, sonographic dimensions of 'single kidneys' were in the upper range of normal paired kidneys and showed adequate growth. 'Compensatory renal hypertrophy' (defined as >95th CI on ≥2 recent measurements) occurred in 1/3 of the patients.
All six patients with CKD and GFR <60 ml/min*1.73m² had pathologic sonomorphology of their 'single kidney' with inadequate renal growth (6/6), abnormal echogenicity (5/6), hypo-/dysplasia (5/6). In addition, proteinuria (5/6) and short stature (3/6) were found.
Conclusions: New reference centiles were generated to assess renal size of 'single kidneys' in paediatric patients. These charts will facilitate counselling of patients and parents. Further evidence for a benign clinical course of children with 'single kidney' and absent additional pathology of the remnant kidney is presented.