• RENO VASCULAR DISEASE.

Synonyms: renovascular occlusive disease, renal vascular disease, atherosclerotic/atheromatous renal artery disease, atherosclerotic renovascular disease (ARVD), renal artery stenosis, renovascular hypertension, ischaemic nephropathy, renal artery fibromuscular hyperplasia

Renovascular disease is the term given to the impairment of renal perfusion caused by disease affecting the arterial supply of the kidney(s).
Renal hypoperfusion leads to hyperactivation of the renin-angiotensin-aldosterone axis, causing hypertension. Renal vascular disease is an important cause of secondary hypertension and chronic kidney disease.

Renal vein thrombosis may cause a similar pattern of disease.

Pathogenesis

• In the developed world, atherosclerosis is by far the most common cause of renovascular disease. This normally develops at the renal artery ostium on the luminal surface of the aorta/proximal renal artery. The atheroma obstructs renal blood flow and leads to chronic renal ischaemia.

• Atheroma may account for >90% of cases in white vascular high-risk populations. Renal artery atheroma is commonly associated with more generalised atheroma and cerebral, cardiac and/or peripheral vascular disease.

• In the Indian sub-continent and the Far East, Takayasu’s arteritis is responsible for about 60% of cases.

• The remainder of renovascular disease is largely due to fibromuscular dysplasia of the renal artery which tends to affect the more distal portions of the renal artery. Fibromuscular dysplasia is an angiopathy of uncertain aetiology that may affect the carotid and vertebral circulation, visceral arteries, and peripheral arteries.Some series estimate that fibromuscular dysplasia may make up to 30% of cases of renal artery stenosis in vascular low-risk groups.

Both atheroma and fibromuscular dysplasia cause unilateral renal artery stenosis in about 75% of cases.

Epidemiology
• The exact prevalence is difficult to estimate, as the condition may easily go undiagnosed among hypertensive patients, and there is an appreciable prevalence of undiagnosed hypertension in the population at large.
• In the USA it is estimated to account for 1-5% of cases of secondary hypertension in the general population, but as much as 30% in vascular high-risk groups, or up to 60% in those aged >70 years.
• In a study of UK type 2 diabetics with hypertension (a high-risk group for renovascular disease) and normal serum creatinine levels, using magnetic resonance angiography to detect the disease, a prevalence of 17% was found. 95% of these patients had unilateral disease.
• The prevalence of angiographic renal artery stenosis in a group of UK patients undergoing angiography for suspected peripheral vascular disease was 36%.
• Atherosclerotic disease is most common among older men.
• Fibromuscular disease is most common among women aged 30-40 years. It can also be a cause of secondary hypertension in children.
• Renal artery stenosis is more common in Caucasian than in Afro-Caribbean populations.

Risk factors.

• Hypertension (but up to 35% of patients with renovascular disease may be normotensive).

• Advanced age (much more common in those aged 60-70 years, with prevalence increasing in those aged >70 years; one unselected postmortem series showed a prevalence of 42% in those aged over 75 years).

• Evidence of renal impairment.

• Evidence of peripheral vascular or cerebrovascular/cardiovascular disease.

• Diabetes mellitus.

• Smoking.

• Family history of cardiovascular disease or renovascular disease.

• Hyperlipidaemia.

• White racial background (approximately twice the prevalence in those with a white racial background compared with African Americans in a group of patients with severe hypertension).

Presentation

The condition may present in a variety of ways and is usually asymptomatic. The following clinical scenarios are relatively common modes of presentation:
• Abrupt onset of hypertension in middle-aged or older patients.

• Severe hypertension.

• Hypertension resistant to standard medical therapy.

• Hypertension developing in a patient with known peripheral-vascular/cerebrovascular/cardiovascular disease.

• Hypertension developing in a patient with no family history of hypertension.

• Biochemical or clinical evidence of renal impairment occurring during treatment withangiotensin-converting enzyme (ACE) inhibitors or angiotensin-II receptor antagonists.

• De novo renal impairment developing in a hypertensive or normotensive patient with vascular disease/risk factors.

• De novo hypertension or renal impairment developing in an older patient who has been previously normotensive.

• Hypertension with hypokalaemia (due to hyperaldosteronism) with no provoking medications or other identifiable cause (may be associated with metabolic acidosis).

• Decompensation of congestive cardiac failure in a hypertensive patient (may present with recurrent episodes of acute pulmonary oedema with no obvious precipitant – so-called ‘flash pulmonary oedema’).

Fibromuscular hyperplasia usually presents with renovascular hypertension or stroke. It can rarely present as subarachnoid haemorrhage, abdominal angina, or claudication of the legs or arms.

Dr G Mohan.

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