List the causes of secondary hypertension. What tests could you order to assess for these diagnoses?
Secondary hypertension is elevated blood pressure that results from an underlying, identifiable, often correctable cause. Only about 5 to 10 percent of hypertension cases are thought to result from secondary causes.
The secondary causes for hypertension can be classified as follows:
- Renal disease.
This may be due to renovascular disease from renal artery stenosis or fibromuscular dysplasia. A clue to this may be acute elevation in serum creatinine after ACE inhibitor or angiotensin II receptor blocker. These can be assessed with renal artery doppler ultrasound, MR angiography and CT angiography. Primary renal disease can also cause hypertension.Look for elevated serum creatinine, hematuria/proteinuria on urine dipstick, and RBCs and RBC casts on urinalysis.
- Endocrine causes.
The endocrine disorders that may cause hypertension include:
- Cushing’s syndrome (elevated 24 hour urine cortisol excretion, loss of normal suppressibility of cortisol secretion by the administration of low dose dexamethasone)
- Pheochromocytoma (increased urinary catecholamine and metanephrine excretion, elevated plasma free metanephrines)
- Primary hyperaldosteronism (elevated plasma aldosterone to plasma rennin activity ratio)
- Primary hyperparathyroidism (elevated serum calcium and PTH)
There are many drugs that can cause hypertension. A few examples are:
- Oral contraceptives
- Monoamine oxidase inhibitors
- Coarctation of the aorta.
May be considered in the setting of hypertension in the upper extremities but low blood pressure in the lower extremities and/or decreased femoral pulses.This diagnosis can be suggested on chest x-ray and diagnosed with echocardiography.
- Sleep apnea.
If suspect from history or physical, this can be assessed with a formal sleep study.