The signs of a passed ureteral stone

Ten patients with typical renal colic fortuitously passed a urinary calculus, which was retrieved during or shortly after excretory urography. Characteristic alterations in the urogram included: (a) no delay in passage of contrast medium down the entire length of the ureter, (b) decreased radiodensity of contrast on the affected as compared to that of the normal side, (c) dilatation of the ureter on the affected side and (d) a hazy appearance of the ureter with poor definition of its borders. Post-obstructive diuresis explains these changes. This constellation of findings, with accompanying absence of an opaque calculus on the plain film, correctly diagnoses a recently passed stone. The sign complex indicates that obstruction has been relieved, even when the calculus remains in situ.