Diagnosis of secondary hypertension: an age-based approach.

Secondary hypertension is a type of hypertension with an underlying, potentially correctable cause. A secondary etiology may be suggested by symptoms (e.g., flushing and sweating suggestive of pheochromocytoma), examina- tion findings (e.g., a renal bruit suggestive of renal artery stenosis), or laboratory abnormalities (e.g., hypokalemia suggestive of aldosteronism). Secondary hypertension also should be considered in patients with resistant hyper- tension, and early or late onset of hypertension. The prevalence of secondary hypertension and the most common etiologies vary by age group. Approximately 5 to 10 percent of adults with hypertension have a secondary cause. In young adults, particu- larly women, renal artery stenosis caused by fibromuscular dyspla- sia is one of the most common secondary etiologies. Fibromuscular dysplasia can be detected by abdominal magnetic resonance imag- ing or computed tomography. These same imaging modalities can be used to detect atherosclerotic renal artery stenosis, a major cause of secondary hypertension in older adults. In middle-aged adults, aldosteronism is the most common secondary cause of hyperten- sion, and the recommended initial diagnostic test is an aldosterone/ renin ratio. Up to 85 percent of children with hypertension have an identifiable cause, most often renal parenchymal disease. Therefore, all children with confirmed hypertension should have an evaluation for an underlying etiology that includes renal ultrasonography.