Medullary sponge kidney disorder is a familial disorder that has autosomal dominant transmission. In some cases, however, the occurrence of medullary sponge kidney disorder can be sporadic. It is estimated that 1 in 100 to 200 individuals have some form of medullary sponge kidney, but many may be asymptomatic. The true incidence may be closer to 1 in 5000 who evidence the disorder. In medullary sponge kidney disorder, the tubules of the kidneys that hold urine are irregular in diameter, forming small cysts of urine in the dilated portions. The dilation and cysts result in a spongey appearance to the kidneys. Associated with the dilation of the tubules is an increased likelihood of calcium deposits forming in the kidneys and subsequent kidney stones. Medullary sponge kidney may not be symptomatic unless calcium deposits are formed. As such, manifestation and identification of the disorder may be associated more with diet than with gender or ethnicity.