Diminished radiopacity of contrast material: a urographic sign of ureteral calculus.

Eleven patients with unilateral ureteral calculus had excretory urography which showed the radiopacity of excreted contrast material to be diminished on the side of the calculus. This finding was of diagnostic importance in nine patients who demonstrated little or no dilatation of the urinary tract proximal to the calculus. Other forms of unilateral renal disease, such as acute pyelonephritis, can produce the same urographic finding.