Simple cysts of the kidney in children.

We discuss 5 children with simple renal cysts, 2 of whom were diagnosed initially as having a Wilms tumor or mesoblastic nephroma. The most common presenting feature of this lesion is a palpable mass, especially in the infant or younger child. In older children characteristic radiographic features can suggest a correct preoperative diagnosis. However, distinguishing a simple cyst and a solid tumor with necrotic degeneration may not be possible in the infant and younger child, and surgical exploration is indicated.