Medullary sponge kidney

Purpose of review After it was first described in 1939, medullary sponge kidney (MSK) received relatively little attention. This was because it was believed to have a low prevalence and because it was considered a benign condition. Studies in recent years have been changing these convictions however, hence the present review. Recent findings Insight has been obtained on the genetic basis of this disease, supporting the hypothesis that MSK is due to a disruption at the ‘ureteric bud–metanephric mesenchyme’ interface. This explains why so many tubular defects coexist in this disease, and particularly a distal tubular acidification defect of which the highly prevalent metabolic bone disease is one very important consequence. In addition to the typical clinical phenotype of recurrent stone disease, other clinical profiles have now been recognized, that is, an indolent, almost asymptomatic MSK, and a rare form characterized by intractable, excruciating pain. Summary Findings suggest the need for a more comprehensive clinical characterization of MSK patients. The genetic grounds for the condition warrant further investigation, and reliable methods are needed to diagnose MSK.