Use of the captopril test to assess renin responsiveness in children with hypertension and renal disease.

The captopril test was performed on 49 children of whom 36 were hypertensive, and the remainder were normotensive but were at risk for developing hypertension because of scarred kidneys secondary to vesico-ureteral reflux. Blood pressure (BP) was monitored in fasting supine patients throughout the duration of the test. Blood was taken for measurement of plasma renin activity (PRA); then captopril (0.7 mg/kg of body weight) was administered orally. A second blood sample was taken for PRA at 90 min postcaptopril. The mean (SEM) PRA at 90 min was 11.90 (4.01) ng/l/s [42.84 (14.44) ng/ml/h] in 7 patients with renovascular disease. In 4 patients with essential hypertension corresponding values were 0.88 (0.38) ng/l/s [3.17 (1.37) ng/ml/h]. Patients with other renal diseases showed variable values. Some individuals had PRA values as high as those of patients with renovascular disease, but the etiology of their hypertension was usually clinically evident. Our preliminary data would suggest that the captopril test may help differentiate between patients with essential hypertension and those with renovascular disease, or may help select patients that should be followed up by more definitive diagnostic procedures.