This is the most common cause of acute renal failure. There is severe damage to the tubular epithelial cells caused by ischaemia or,less often,by nephrotoxic substances.
There is reduced glomerular filtration and selective reabsorption and secretions by the tubeless,leading to:
- Heart failure due to fluid overload.
- Generalised and pulmonary oedema.
- Accumulation of urea and other metabolic waste products.
- Electrolyte imbalance which may be exacerbated by the retention of potassium released from damaged cells anywhere in the body.
- Acidosis due to hydrogen ion retention.
Profound diuresis occurs during the healing process then the epitherial cells of the tubules have regenerated but are still incapable of selective reabsorption and secretion. Diuresis may lead to acute dehydration,complicating the existing high plasma urea,acidosis and electrolyte imbalance. If the patient survives the initial acute phase,a considerable degree of renal function is usually restored over several weeks.
CAUSES OF ATN.
- Ischaemia- severe shock,dehydration,haemorrhage,trauma.
- Drugs eg aminoglycoside antibiotics,non-steroidal anti-inflammatory drugs.
- Haemoglobinaemia- accumulation of haemoglobin,released by haemolysis of red blood cells.
- Myoglobinaemia- accumulation of myoglobin,released from damaged muscle raises blood levels.
