Increased adrenal production of aldosterone in response to nonpituitary, extra-adrenal stimuli such as renal hypoperfusion

Aetiology

• Reduced renal blood flow leads to excess renin (and hence angiotensin II)
• Causes of reduced renal blood flow include:
  • Obstructive renal artery disease (eg, atheroma, stenosis)
  • Renal vasoconstriction (as occurs in accelerated hypertension)
  • Oedematous disorders (e.g. heart failure, cirrhosis with ascites)

Renal artery stenosis

• Most cases are caused by atheroma but in younger females it can be the result of fibromuscular dysplasia
• Juxtaglomerular apparatus (juxtaglomerular cells and macula densa) is fooled into thinking this is low blood pressure and there is secretion of renin and so these patients develop hypertension

Clinical features

• Hypertension

Investigations

• Renin/aldosterone ratio: high aldosterone and high renin indicates secondary hyperaldosteronism
• Imaging: doppler ultrasound, CT angiogram or magnetic resonance angiography (MRA) to look for for renal artery stenosis or obstruction

Management

• Aldosterone antagonists e.g. spironolactone
• Treat underlying cause e.g. percutaneous renal artery angioplasty via the femoral artery to treat in renal artery stenosis