[Improvement in the informativeness of diuretic kidney function scintigraphy by calculation of a washout index]

Diuresis renography after administration of 123I-(131I-)Hippuran of 248 patients (492 kidneys) were compared retrospectively with clinical findings, history, i.v. urography, and ultrasound examinations. A new wash-out-index was calculated. In cases with obstructive dilatation of the collecting system this index was smaller than 0.9. If it was 0.9 to 1.2 additional diagnostic procedures seem necessary. An index more then 1.4 excludes obstruction. The shape of the renogram curve after furosemide is important for the diagnosis too. A concave shape was found in non-obstructive dilatation, a convex shape in obstructive dilatation of the renal pelvis. The wash-out-index is a reliable parameter if cases with reflux, lower ureteral obstruction and shrunken kidneys are excluded.