Intravenous pyelography is often utilized as a diagnostic aid to help clarify many different clinical problems. When both kidneys are visualized by this technique many problems can be solved. Occasionally one side will fail to concentrate the urographic medium. When this situation is found some interesting questions arise: 1. Why did one side fail to concentrate the media? 2. What further examinations are necessary to make the diagnosis? 3. What should be looked for in making the diagnosis? To help clarify the problem of differential diagnosis a series of such cases was reviewed. Seventy cases from the Seattle Veterans' Administration Hospital, King County Hospital, and the Children's Orthopedic Hospital were collected and reviewed. No attempt was made to establish the incidence of this problem.
The cases were divided into three groups: (1) primary diseases of the genitourinary tract, (2) diseases in which the diagnosis is not completely certain or has