It is often necessary to divert the urinary stream while an obstructive lesion is corrected. This, in reality, is one of the fundamental principles of certain surgical procedures on the urinary excretory apparatus. The obstructive untreated uropathies will eventually destroy the renal parenchyma. If the obstruction can be relieved in whole or in part after a definitely increasing nephrosis is discovered, the recovery of the renal parenchyma is one of the amazing features of the convalescent period. No matter how badly damaged the renal parenchyma may seem to be, none of these cases are necessarily hopeless, even if a single renal mass is the only renal substance that can be found. We have all seen cases in which life has been indefinitely prolonged, with normal blood chemistry balance and only infinitesimal amounts of glomerular tissue clinging to the renal capsule. Equally if not more amazing is the ability of a