Imaging of renal cystic diseases.

The improved understanding of hereditary cystic diseases is changing the nomenclature used to describe these diseases. Detailed family studies of the inheritance of these conditions become possible as the genes involved, or their DNA markers, are identified. At the same time, ultrasonography allows cystic disease to be detected very early in life in some patients. The new information necessitates changes in the terminology, which was based previously on the patient's age at clinical presentation. Thus, because ultrasonography now sometimes identifies the cysts of adult polycystic kidney disease in utero or in neonates, the term autosomal dominant polycystic kidney disease is now more appropriate. Similarly, the term autosomal recessive polycystic kidney disease is replacing infantile polycystic kidney disease. Despite the success of ultrasonography in identifying the cysts of these and other inherited conditions very early, it is important to appreciate that precise definition of the type and heredity of the condition concerned requires detailed pathologic and genetic studies. The other renal cystic disease receiving considerable attention in the recent literature is acquired cystic disease, about which more data are accumulating. With increasing numbers of patients on long-term dialysis, the condition and its complications, especially renal adenocarcinoma but also hemorrhage, continue to cause concern. The evidence for an increased incidence of renal cell carcinoma has strengthened over recent years, and the debate on the need for CT screening of patients on long-term dialysis continues.