Secondary hypertension

Definition

High blood pressure with an identifiable cause

Epidemiology

About 5% of every case of hypertension. It is more likely to have a cause in young patients.

Pathophysiology

The main causes of secondary hypertension are:

1. Cardiac
2. Peripheral
3. Blood volume

The picture on the right might clear this up a little.

Differential

Renal

• Renal artery stenosis makes the kidneys poorly perfused. They interpret this as low pressure, and so try to increase cardiac output with the renin-angiotensin system.
• Renal failure causes fluid build up.

Endocrine

• Primary hyperaldosteronism

Other causes are:

• Pregnancy
• Drugs
• Coarctation of the aorta, lead poisoning and porphyria during acute attacks.

Clinical features

These are features where you need to suspect an underlying cause:

• Age of onset - >50 or <20 years old
• Severely high - >180/110 or evidence of end-organ damage
• Radio-femoral delay - a sign of coarctation of the aorta
• In renal disease
  • Renal artery bruit - renal disease
  • Mass in flank - potential renal mass caused by renal disease
  • FHx of polycystic kidneys
• Endocrine
  • Cushing's - causes excess cortisol, which increases vasocontriction, increasing blood pressure.
  • Conn's - causes excess aldosterone, which causes hypervolaemia.
  • Phaeochromacytoma - can present as sudden episodes of palpitations, with accompanying hypertension.

Investigations

Not all hypertensive patients are investigated as 95% have essential hypertension where no cause can be found. However, if there is any suspicion, the appropriate test should be done. This is list of investigations to rule out common causes of secondary hypertension.

Bloods

• Serum potassium - hypokalaemia is a sign of Conn's, Cushing's, renovascular disease and diuretics
• Serum calcium - hypercalcaemia
• TFTs - hyperthyroidism can cause high blood pressure

Urine

• 24 Urinary VMA - used in diagnosing phaeochromacytoma
• MSU - cells, casts and proteins
• urinary free cortisol - adrenal dysfunction
• renal USS, IVU, renal arteriography

Imaging

• CXR - for end-organ damage

Management

This depends on the cause. Treat the cause. Clever, eh?