Incidental hydronephrosis on bone scintigraphy: sonographic verification.

We studied 98 kidneys in 55 patients with bone scintiscans and renal sonography. Among the 29 kidneys in which hydronephrosis was suspected on bone scintiscans only 12 were truly hydronephrotic by renal ultrasound. In the other 17 cases extrarenal pelves, postural stasis, early urinary tract obstruction or renal parenchymal disease may have contributed to the discrepant findings. By ultrasound criteria there were no false negative readings for hydronephrosis on scintiscan. While it is safe to interpret absence of hydronephrosis caution should be used in diagnosing hydronephrosis, since less than half of the cases actually will have the disease when suspected on a bone scintiscan.