The Crescent Sign

In 1962, Dunbar et al. (1) reported a “crescent” sign in hydronephrosis. This sign was attributed to the contrast material in collecting tubules that had changed their orientation by approximately 90 degrees so as to lie parallel to the renal convexity and close to its surface. This change in orientation is caused by increased pressure in the renal collecting system and is seen only in severe hydronephrosis. It is detectable during the early phases of intravenous pyelography and then disappears as calyces and pelvis are opacified. It is our purpose to present a case of hydronephrosis secondary to ureteropelvic stricture that appears to document Dunbar's explanation for the crescent sign. Case Report J. H. B., a 4-month-old white male, was hospitalized Jan. 4, 1963, because of an upper respiratory infection of ten days duration. The mother reported the presence of a protuberant abdomen since birth and an abdominal mass observed for the first time on the day of admittance. Physical examination revealed a we...