A prospective study was conducted to determine the possibility of obstructive
hydronephrosis in
horseshoe kidney found incidentally in school children and adolescents by using a
radionuclide diuretic renogram. In a 2-year period, 22 school children and adolescents with
horseshoe kidney were found in a mass renal sonography survey. They each underwent a
99mTc dimercaptosuccinic acid renal cortical scan to confirm the
horseshoe kidney. Each
diuretic renogram was performed with the patient in the supine position to rule out obstructive
hydronephrosis. The patients were advised to empty their bladders before the
intravenous injection of
furosemide (1 mg x kg(-1)). The half-time for the clearance of radioactivity from the renal pelvis were calculated. Of the 22 patients, asymmetrical renal cortical function between the two kidneys was found in 14 (63.6%). Eleven kidneys (11/44, 25%) showed stasis of radioactive urine in the renal pelvic region prior to injection of
furosemide. There was no incidence of bilateral
hydronephrosis in these 22 patients. Only one kidney (1/44, 2.3%) showed obstructive
hydronephrosis and five showed clearance of radioactive urine stasis from the renal pelvis immediately after standing up for voiding. There is a low percentage of obstructive
hydronephrosis in these cases of
horseshoe kidney found incidentally in children and adolescents. A follow-up cohort study on these patients would be valuable for monitoring the development of complications.