The explanations advanced to account for cystic kidney, by which is meant total polycystic transformation nearly always associated with great increase in size, may be divided into three sets, and we may speak of the retention theory, the cystadenoma theory, and the malformation theory of cystic kidney.
Virchow (1847) was the father of the retention theory, which assumes that the cysts arise as the result of obstruction to the outflow of urine from the kidney. Many varieties of possible forms of obstruction have been enumerated. Virchow first suggested uric acid deposits, but a little later he adopted the view that the obstruction was the result of a papillitis or pyelonephritis. At the present time the retention theory does not seem to find much favor with those that study the subject closely, and for various reasons, but more particularly because the structure of the cystic kidney is not simply that of