- Characterised by rapid decline in GFR over daysweeks with accumulation of nitrogenous waste
- Often noticed by rapidly rising serum creatinine and urea, accompanied by reduced urine output
- p/c: fluid overload, nausea, malaise, encephalopathy
- o Reduced/inadequate perfusion and inability of post-glomerular arteriole to constrict
- o If these two mechanisms fail = GFR falls = kidney fails
- o Causes: hypovolaemia (haemorrhage/severe D&V), cardiogenic shock (pump failure), sepsis, drugs (ACEi/NSAIDs), severe liver disease leading to renal failure (=’hepatorenal syndrome), burns.
- o Histological pattern in response to this type of injury = acute tubular necrosis (ATN) – usually recovers after several weeks. Concentrating ability of kidney lost and urinary sodium >409mmol/L
- o In prolonged hypotensive insults = acute cortical necrosis (less likely to recover).
- o Many causes = glomerulonephritis, vasculitis, nephrotoxic drugs (gentamicin, NSAIDs), rhabdomyolysis, interstitial nephritis, haemolytic/uraemic syndromes, multiple myeloma…
- o Urinary tract obstruction leading to backed up waterworks and renal failure
- o Common causes: BPH, carcinoma of prostate, ureteric stones, tumours of renal pelvis/ureters/bladder/cervix. External compression of ureters by tumour, retroperitoneal fibrosis. Advanced renal failure will only occur in both kidneys are obstructed.
- Rapid diagnosis is key as some causes are reversible.
- Examine bladder, prostate, look for hypovolaemia (=decreased skin turgor, tachycardia, hypotension, postural hypotension [loss of >20mmHg on standing], low CVP, fluid challenge and observe urine output).
- Renal USS to examine obstructions/hydronephrosis/size (big = waterlogged/malignancy/cysts. Small = chronic renal failure)/symmetry
- Blood tests and urinanalysis – for casts, RBCs, protein
- Ensure adequate oxygenation and circulation
- Avoid fluid overload as this will cause pulmonary oedema. If dry – fluid replete with IV fluids. If overloaded – haemodialysis/haemofiltration/peritoneal dialysis.
- Also be aware in ARF, risk of hyperkalaemia (K >6mmol/L) =dysrhythmias, with peaked T waves, widened QRS, absent P waves, and sine wave appearance.
- Tx: IV calcium, insulin, glucose, calcium resonium, dialysis
- Other complications: metabolic acidosis, encephalopathy, pericarditis.