Secondary hypertension. A streamlined approach to diagnosis.

Among the many potential causes of secondary hypertension are renal parenchymal disease, occlusive renal arterial disease, adrenocortical abnormalities, and pheochromocytoma. Renovascular hypertension can result from either renal parenchymal or occlusive renal arterial disease. Laboratory testing can help in identification and differentiation. Parenchymal diseases usually modify the urine substantially without producing urographic abnormalities, while occlusive arterial lesions produce urographic abnormalities but the urine remains normal. The diagnosis of renal occlusive arterial disease is best defined by arteriography. The only definite criterion for the existence of hypertension of renal origin is cure by either nephrectomy or renal revascularization. Adrenocortical causes of hypertension include enzymatic deficiencies, Cushing's syndrome, and primary aldosteronism. In enzymatic deficiencies, the physical findings provide the most important clues to the type of enzyme deficiency involved. In Cushing's syndrome, accurate determination of the cause of the hypercortisolism is important in terms of choice and success of treatment. The diagnosis of primary aldosteronism rests primarily on the demonstration of nonsuppressible aldosterone excretion rate during salt loading; the presence of inappropriate kaliuresis and/or suppressed plasma renin activity provides corroborative evidence of primary aldosteronism, but the absence of either or both does not preclude the diagnosis. Pheochromocytoma, although rare, is a serious and potentially fatal cause of hypertension. Definitive diagnosis depends on laboratory test results, and the tumor is usually localized by computed tomography.