Does medullary sponge kidney cause nephrolithiasis?

The prevalence of medullary sponge kidney in patients with nephrolithiasis and the issue of whether or not medullary sponge kidney has a role in the pathogenesis of renal stones are controversial. We studied the excretory urograms of 280 patients with nephrolithiasis and 280 patients without either nephrolithiasis or a history of renal stones to determine the frequencies of medullary sponge kidney in the two groups. The criterion for the diagnosis of medullary sponge kidney was the presence of a minimum of three linear or round collections of contrast material within one renal papilla. In the patients with nephrolithiasis, we also looked for biochemical evidence of metabolic causes of renal stones. The frequency of medullary sponge kidney was 12% in patients with nephrolithiasis compared with 1% in patients without nephrolithiasis. The statistical difference was highly significant (chi square = 27.1; p less than .001). Metabolic disorders accounting for the lithiasis were detected in 93% of the patients with stones without medullary sponge kidney. Such evidence was present in 60% of patients with stones and medullary sponge kidney. The statistical difference was significant (chi square = 25.8; p less than .001). Our results suggest that medullary sponge kidney is a cause of nephrolithiasis.