acute kidney injury Flashcards
define ‘acute kidney injury’
acute decline (<48 hours) in kidney function with a rise in serum CK and/or reduced urine out put (oligouria)
AKI diagnosis
- an absolute rise in serum CK by 26.6 micromol/l
- increase in CK by >50%
- oligouria <0.5ml/kg/hour for >6 hours
common causes of AKI
sepsis, diabetes, old age (multimorbidity), iodinated contrast, MI, hypertension, drug OD, connective tissue disorder, drug toxicity
name some nephrotoxic drugs
NSAIDs, ACEi, lithium, diuretics, chemotherapy, aminoglycosides, cotrimoxazole, trimethoprim
what effect does renin have on GFR
renin causes vasoconstriction of the efferent arteriole which increases GFR
how can an ACEi worsen renal function?
ACEi blocks the production of Ang II, leading to dilation of the efferent arterioles. this causes a reduction in GFR and reduced renal perfusion and hyperkalaemia.
what is acute tubular necrosis?
ATN occurs due to reduced renal perfusion (renal ischaemia). it is also due to contrast injury.
brown granular casts on microscopy indicate what pathology?
acute tubular necrosis
pre-renal (functional) causes of AKI?
VOLUME DEPLETION hypovolaemia heart failure nephrotic syndrome sepsis drugs hepatorenal syndrome renal artery occlusion/stenosis
renal (structural) causes of AKI?
glomerular disease (SLE, vasculitis) glomerulonephritis lymphoma infiltration contrast nephropathy - ATN HUS/thrombic microangiopathy cholesterol emboli
post-renal (obstructive) causes of AKI?
urogenital obstruction renal calculi tumours extrinsic pressure strictures
typical U&Es results of AKI
high sodium
high potassium
high uraemia
high CK
when would you do a renal biopsy in AKI?
if patient is not improving, if auto Igs are found or if rapidly progressive GN is suspected.
complications of AKI?
hyperkalaemia uraemic pericardial effusion severe acidosis severe uraemia fluid overload
ECG findings which indicate hyperkalaemia?
arrhythmias, weak muscles tall tented T waves wide QRS loss of P waves can lead to asymptomatic VF.VT
