The term “cystic kidneys” is used to describe a heterogeneous group of conditions characterised either by single/multiple cysts or abnormal kidneys with no obvious cysts as the kidney may appear hyperechoic (solid). Confusion has arisen because the terminology is imprecise at times and multiple cysts do not necessarily denote a heritable condition or specific syndrome. The disorders span all ages in childhood and since the introduction of routine antenatal ultrasound many are identified antenatally.

The ultimate diagnosis of many of the “cystic kidneys” requires clinical, genetic, radiological, and pathological information. Errors arise when insufficient information is gathered and collated. A precise diagnosis is important for prognosis, treatment, and genetic counselling although this may not be possible at presentation.1-3 As the aetiology, histology, and clinical presentation are diverse, no single classification of “cystic renal disease” is satisfactory; the most widely acceptable classification is genetic and non-genetic (see table 1). A morphological classification of “cystic kidneys” however remains useful for the non-genetic disorders. Classification of a particular child's “cystic kidneys” requires information about any relevant family history; parental consanguinity; relevant histopathology if available, and ultrasound of parents and siblings. Full clinical evaluation, evidence of a syndrome or dysmorphic features, assessment of renal function, and any antenatal ultrasound findings are all important. Extrarenal manifestations occur and ultrasound examination of liver, pancreas, and spleen is mandatory.