[Pathologic development of the kidney]

In the absence of firmly established views on the development of nephropathy, we describe in this paper the embryogenetic and clinical aspects of kidney disease. Congenital reductive nephropathy always arises in the ureteral bud and is determined by two factors, endogenous dysplasia and endogenous obstruction. The nine well-known patterns of disease that may result are described herein. The most important starting points are as follows: (a) A dysplastically disorganized and hence refluxive trigone of the bladder induces, via pyramidal-medullary deficiencies, a defect of the metanephros and thus what we term reflux nephropathy (III-V). BU and PN may supervene postnatally. (b) Similarly, obstruction of the ureteral outlet in the first trimester induces dysplastic ascending nephropathy. (c) The same obstruction beginning in the second trimester induces nondysplastic, purely obstructive nephropathy, characterized by glomerular hypogenesis and hemo-obliterative cirrhosis which varies considerably from stage to stage and from case to case and may go as far as complete loss of the parenchyma. (d) Obstruction of the pyeloureteral junction, occurring late in the embryonic phase and originating outside the urinary system, provides the clearest example of fully developed nondysplastic reductive nephropathy. The lesional process may come to a halt at any time. (e) Coincidence of early embryonic dysplastic-refluxive nephropathy and late embryonic infravesical obstruction (with no causal link) accounts for half the morbidity from valvular disease. The other half results from simple nondysplastic obstruction.