Normal development and experimental models of cystic renal disease

From a review of renal development and experimental cystic disease, the following observations can be made: 1. The previous theories developed to explain cystic renal disease (nonunion, failure of regression, and obstruction to urine flow) do not adequately fit with the numerous recent observations made in studies of most experimental models or in human renal cystic disease. 2. The most acceptable theory to date for most types of renal cystic abnormalities (except those due to known obstruction of urine flow) is that abnormalities of the tubular supporting wall occur, probably as a result of toxic or metabolic injury to the tubular cells of the wall and the related interstitial tissues, which are exposed to the highest concentrations of these compounds. This theory would also help explain the etiology of cystic renal diseases in man and should lead to attempts to isolate toxic factors or enzyme abnormalities in susceptible families and in early cases. 3. Induction of cystic abnormalities through a variety of experimental manipulations and drugs reveals impressive strain, sex, and species variability, and these differences should be more carefully examined. 4. The same chemical that induces a cystic change in the mature, fully developed kidney may cause changes which are quite different (location, severity, etc.) in both the fetal and newborn kidney, in which continual nephrogenesis is occurring. 5. Many of the previous explanations of cystic changes require careful reinterpretation of the findings (to reconcile certain differences), and confirmatory studies should be performed to help piece together some of the puzzling observations noted, such as the cystic changes seen with adrenocorticosteroids, and their relationship to potassium depletion.