Acute kidney injury (AKI) Flashcards
Definition of acute kidney injury (AKI)
An abrupt (<48 hours) reduction in kidney function defined as:
- An absolute increase in serum creatinine by >26.4umol/L
- OR increase in creatinine by >50%
- OR reduction in urine output
What are the 3 classes of cause of AKI?
Pre-renal - Impaired blood flow
Renal - Damage to renal cells
Post-renal - Obstruction
Pathophysiology of pre-renal AKI
Reversible volume depletion causes a reduction in perfusion to the kidneys - leads to oliguria (<0.5 mls/kg/hr) and increase in creatinine
What are some types of cause of pre-renal AKI?
- Hypovolaemia
- Hypotension
- Renal hypo perfusion
What are some causes of hypovolaemia in pre-renal AKI
Haemorrhage
Volume depletion (D+V, Burns)
What are some causes of hypotension in pre-renal AKI?
Cardiogenic shock
Distributive shock (Sepsis, anaphylaxis)
What are some causes of renal hypo perfusion in pre-renal AKI?
NSAIDs/COX2
ACEi/ARBs
Hepatorenal syndrome
How does ACEi cause AKI?
- Renin reduces renal perfusion and increases angiotensin II, which causes efferent arteriole vasoconstriction, to maintain GFR
- ACE inhibitors decrease levels of angiotensin II and so decrease efferent arteriole vasoconstriction, therefore slightly lowering GFR
- If there is a co-morbid reduction in renal perfusion, GFR can fall rapidly, causing AKI
What are some types of cause of renal AKI?
- Vascular
- Glomerular
- Interstitial nephritis
- Tubular injury
What can occur if pre-renal AKI goes untreated?
Acute tubular necrosis
What are some vascular causes of renal AKI?
Vasculitis (GPA)
Renovascular disease (Like peripheral vascular disease for the kidneys)
What is a glomerular cause of renal AKI?
Glomerulonephritis (And therefore any causes of GN)
What are some causes of interstitial nephritis in renal AKI?
- Drugs
- Infection (TB)
- Systemic (sarcoid)
What are some causes of tubular injury in renal AKI?
- Ischaemia
- Drugs (gentamicin)
- Contrast
- Rhabdomyolysis
What is the pathology of post-renal AKI?
AKI due to obstruction of urine flow leading to back pressure and thus loss of concentrating ability
What are some causes of post-renal AKI?
- Stones
- Cancers
- Strictures
- Extrinsic pressure
What are some patient factors that increase risk of AKI?
- Older age
- Male
- CKD
- Diabetes
- Cardiac failure
- Liver disease
- Peripheral vascular disease
- Previous AKI
What are some exposures that can increase risk of AKI?
- Hypotension
- Hypovolaemia
- Sepsis
- Deteriorating NEWS
- Recent contrast
- Exposure to certain medications
What classification system is used in AKI cstaging?
KDIGO staging
What are some symptoms of AKI
- Constitutional symptoms - anorexia, weight loss, fatigue, lethargy
- Nausea and vomiting
- Itch
- Fluid overload - oedema, SOB
What are some signs of AKI?
- Fluid overload including HTN, oedema, pulmonary oedema, pleural effusion
- Uraemia including itch, pericarditis
- Oliguria
What are some investigations required in AKI?
U+E
Bloods
Urinalysis
USS
Immunology
What blood tests are required in AKI?
- FBC - Anaemia
- Coagulation screen - Abnormal clotting
- Bicarbonate
- Bone profile
What specific tests are required if myeloma is the suspected cause of AKI?
Protein electrophoresis
Bence-Jones protein
How is pre-renal AKI managed?
Assess for hydration
Fluid challenge for hypovolaemia
How is hydration assessed in pre-renal AKI?
- Clinical observations (BP, HR, UO)
- JVP, cap refil, oedema
- Pulmonary oedema
How is fluid challenge completed in hypovolaemia in pre-renal AKI
- Crystalloid (0.9% NaCl) or colloid (Gelofusin) - no NOT use 5% dextrose
- Give bolus of fluid then reassess and repeat as necessary
- Ig >1000mls IN and no improvement, seek help
What are some management options in pre-renal and renal AKI?
- Fluid resuscitation
- Treat underlying causes
- Stop nephrotoxins
- Dialysis is remains anuric and uraemic
How is post-renal AKI managed?
- Relieve obstruction - catheter, nephrostomy
- Refer urology if ureteric stenting required
What are some urgent indications for haemodialysis in AKI?
- Hyperkalaemia >7 or >6.5 unresponsive to medical therapy
- Severe acidosis - pH <7.15
- Fluid overload e.g. pulmonary oedema
- Urea >40, pericardial rub/effusion
What are some complications of AKI?
- Hyperkalaemia
- Fluid overload (pulmonary oedema)
- Severe acidosis (pH <7.15)
- Uraemic pericardial effusion
- Severe uraemia(Ur >40)
What is acute tubular necrosis?
Refers to tubular cell death and acute deterioration in renal function
What is the most common cause of acute tubular necrosis?
Ischaemia:
- Hypotension
- Shock
- Malignant hypertension
- Polyarteritis nodosa
- HUS
What are some other causes of acute tubular necrosis?
Toxins or drugs
Post renal ATN (Obstruction)
