Approach to hypertension diagnosis

It is important to diagnose the cause of hypertension and treat it if it is significant, but equally important to avoid diagnosing or labeling a patient as hypertensive when pressures are normal or transiently elevated. Overdiagnosis leads to unnecessary and expensive tests, and false labeling may adversely affect the subject's application for work or life insurance.

A diagnostic evaluation is undertaken in children whose blood pressures are repeatedly above the 95th percentile. Diagnosis is approached by knowing the causes of hypertension (Tables 22-22, 22-23, and 22-24) and relating these to findings ascertained from a complete history and physical examination (Tables 22-25 and 22-26) and from basic laboratory tests (Table 22-27). Most of the common causes of hypertension will usually be evident after this evaluation and can be addressed as appropriate. If no cause is discovered, and if blood pressure remains near the 95th percentile, the child is observed at 3- to 6-month intervals. Mild hypertension in children does not require treatment, and elaborate studies to identify its cause are not warranted. A schema for diagnosis is given in Fig. 22-89.

In children with more severe hypertension, the decision to proceed with further testing is influenced by several factors. The younger the child with significant hypertension or the higher the blood pressure, the more likely there is to be a correctable cause, and thus, further investigations should be pursued. If the child is markedly overweight, obesity is the likely cause. If there is a strong family history of essential hypertension, particularly in an adolescent patient, there is less need to look for another cause.

The more intensive investigations listed in Table 22-28 are used to diagnose renal and endocrine abnormalities, including tumors.

MINERALOCORTICOIDS Patients with aldosterone-secreting tumors or hyperplasia of the adrenals may develop hypertension. This is usually associated with hypernatremia, hypokalemia, metabolic alkalosis, increased plasma volume, a low and fixed plasma renin level, and increased aldosterone secretion rates. Serum electrolytes provide a fairly good screening test for this disorder, and they can be followed by measuring peripheral renin levels after 2 hours in the erect position. Persistently low renin levels then indicate the need for the more time-consuming and expensive measurements of aldosterone concentrations or secretion rates as well as tests to determine if aldosterone can be suppressed by giving a high salt intake and dexamethasone. Low renin activity does not prove mineralocorticoid excess because renin is low in about 20% of patients with essential hypertension.