pathophys of AKI - amboss Flashcards
define AKI
sudden loss of renal function with a subsequent rise in creatinine and blood urea nitrogen BUN
three main causes of AKI
decreased renal perfusion (prerenal)
direct damage to kidneys (intrarenal/intrinsic)
inadequate urine drainage (post renal)
diagnosis of AKI is made based on
increase in serum creatinine concenration and/or decrease in urine output
prerenal causes of AKI
decreased blood flow into kidneys may be due to
- absolute loss of fluid: haemorrhage, vomiting, diarhoea, severe burns, poor oral intake, diuretics
- relative loss of fluid: hypotension, distributive shock, congestive heart failure
- local to the renal artery: renal artery stenosis, embolus
pathophysiology of prerenal AKI
less blood is pumped to glomeruli
less blood filtered
decreased glomerular filtration rate (GFR)
azotaemia
high levels of nitrogen containing compounds in the blood
signs of prerenal AKI
oliguria - low urine
azotaemia - high urea and creatinine in blood
BUN:creatinine ratio of >20:1
concentrated urine
intrarenal AKI is due to
damage to the tubules, glomerulus or interstitium
eg.
- acute tubular necrosis via ischaemia (usually due to a prerenal decrease in blood flow) or via nephrotoxins
- glomerulonephritis
- acute interstitial nephritis
- vascular diseases
causes of acute tubular necrosis
ischaemia eg. due to prolonged hypotension
nephrotoxic drugs:
aminoglycosides (antibiotics)
cisplatin, methotrexate
radiocontrast dye
poisons:
lead
ethylene glycol
endogenous toxins:
uric acid (tumour lysis syndrome)
haemoglobin in intravascular haemolysis
myoglobin released from damaged muscles n rhabdomyolysis
glomerulonephritis
inflammation of the glomerulus
often caused by antigen antibody complexes causing inflammation and damage
cells lining glomerulus
podocytes
signs of intrarenal AKI
proteinuria and haematuria due to damaged podocytes
decreased GFR due to fluid leakage causing. reduced pressure difference
oliguria
more fluid in the blood: oedema and. hypertension
azotaemia
acute interstitial nephritis
infiltration of immune cells
canbe caused by NSAIDs, diuretics, penecillin
oliguria and eosinophiluria
failure to cease medications causing acute interstitial nephiritis may lead to
renal papillary necrosis
where the renal papillae are destroyed
how common in prerenal
60% of AKIs
cardiorenal syndrome
a spectrum of conditions affecting cardiac and renal systems when dysfunction in one organ results in dysfunction of the other
eg. congestive heart failure causing poor renal perfusion
hepatorenal syndrome
kidney injury in patients with cirrhosis