Medullary cystic disease complex may manifest in the infantile, juvenile, or early adulthood periods. Cysts may be microscopic or macroscopic and predominantly involve the medulla or corticomedullary junctions. It is the most common cause of end-stage renal disease in this age group and is caused by genetic mutations. 

In the infantile type, the kidneys may be enlarged on presentation, as in this case. In the juvenile or adult type, they are often small or normal-sized.

Ultrasound is the modality of choice for initial imaging and for follow-up imaging.