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VASCULAR CAUSES OF ACUTE KIDNEY FAILURE
Specific causes of acute kidney failure
▪
Prerenal
failure and acute tubular necrosis
▪
Vascular causes of acute
kidney
failure
▪
Nephrotoxic causes of acute
kidney
failure
▪
Glomerulonephritic and vasculitic causes
of
acute kidney failure
▪
Interstitial nephritis as a cause of acute
kidney
failure
▪
'Haematological' causes of acute
kidney
failure
▪
Hepatokidney Syndrome
▪
Tropical
Vascular causes of acute kidney failure
Small-vessel obstruction
Accelerated-phase hypertension
'Accelerated-phase' hypertension (a term preferred to
'malignant' hypertension because the implication of malignancy
is terrifying for patients) occurs when the blood pressure is
elevated sufficiently to cause fibrinoid necrosis of blood
vessels, leading to the development of haemorrhages and exudates
in the ocular fundi. It may develop as a consequence of
pre-existing
kidney
disease, but does not always do so, and is itself a potent cause
of
kidney
damage.
Acute
kidney
failure is a common complication in those with previously normal
kidney
function, and is associated with proteinuria, haematuria, and
the presence of urinary red cell casts. The higher the
creatinine at presentation, the poorer the prognosis for both
patient survival and
kidney
outcome: in one study only 9 per cent of those with an initial
plasma creatinine below 300 µmol/l progressed to need
kidney
replacement therapy, compared with two-thirds of those with a
plasma creatinine above this level.
The ability of the kidney to autoregulate perfusion is disturbed
in accelerated-phase hypertension, hence the therapeutic
lowering of arterial pressure may be associated with reduced
kidney
perfusion and an abrupt decline in renal function.
Accelerated-phase hypertension is one of the conditions in which
renal function sometimes recovers after a lengthy period on
dialysis.
Kidney
failure was the cause of two-thirds of the deaths in patients
with accelerated-phase hypertension in the days before dialysis
was available.
Systemic sclerosis
This disease does not usually involve the kidney, but a syndrome
resembling accelerated-phase hypertension and termed
'scleroderma
kidney
crisis' is well recognized in patients with diffuse cutaneous
systemic sclerosis. It usually occurs within the first 5 years
of the disease, may be the presenting feature, and often appears
during the winter months. Rapid worsening of skin manifestations
may precede the crisis, but frequently there is no warning.
The patient may develop headaches, visual disturbance, and
convulsions. Arterial pressure is usually grossly elevated, but
the
kidney
syndrome can occur without a rise in arterial pressure.
Haemorrhages and exudates are often seen in the ocular fundi.
Kidney
failure, with proteinuria and haematuria, develops rapidly. A
microangiopathic haemolytic anaemia may complicate the
situation. Plasma levels of renin are grossly elevated.
There have been a number of case reports of arrest or reversal
of the syndrome after treatment with angiotensin-converting
enzyme inhibitors or nifedipine. These agents should be tried,
but more in hope than expectation that they will prevent
relentless progression to endstage
kidney
failure.
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