Malignant hypertension in children secondary to chronic pyelonephritis: laboratory and radiologic indications for partial or total nephrectomy.

: Severe renin-mediated hypertension was noted in 2 children as a result of selective renal damage from vesicoureteral reflux during the early years of life. In each case the reflux had been corrected successfully long before hypertension developed. In 1 case the late damage involved only 1 kidney and nephrectomy resulted in immediate relief of the hypertension. In the second case, even though both kidneys showed segmental scarring from calicectasis and chronic pyelonephritis, removal of the atrophied lower pole of 1 kidney made hypertension amenable to medical treatment and reduced excessive renin output to a fraction of the original high levels. The mechanism of renin-mediated hypertension in kidneys with segmental scars of chronic pyelonephritis is believed to be ischemia of the relatively normal renal cortex in proximity to areas of interstitial fibrosis, within which are tortuous interlobular and smaller arterioles with severe intimal thickening. Hypertrophy of normal renal segment occurs in young patients with segmental chronic pyelonephritis. To accommodate this enlargement the original calix develops an extension or elongation readily distinguishable from other dilated calices.