Medullary sponge kidney and congenital total hemihypertrophy

The incidences of medullary sponge kidney and congenital total hemihypertrophy in the general population are estimated at 0.005 and 0.001% respectively. The concurrence of these two diseases in 17 cases, representing 5 to 10% of all patients with total hemihypertrophy, is greater than that to be expected for the coincidence of 2 independent conditions. Because both diseases are developmental anomalies, this concurrence most probably reflects an underlying defect of ontogeny, the nature of which remains obscure. The clinical picture of patients with combined medullary sponge kidney and congenital total hemihypertrophy bears many similarities to that expected for each condition alone. However, comparative analysis of the manifestations of these diseases when independent and when concurrent seems to demonstrate a beneficial modification of the natural history of total hemihypertrophy by concurrent sponge kidney disease. Those patients with both diseases appear to constitute a subgroup of total hemihypertrophy in which there is a decreased incidence of mental retardation and of diverse congenital anomalies. Because of the limited case material available in the literature, careful clinical observation in additional patients will be required for verification of this observation.