Pre-renal AKI
What is the most common broad cause of a pre-renal AKI
What is reduced renal perfusion e.g. hypovolaemia
What does intrinsic AKI mean?
What is damage to the kidney itself (tubules, glomeruli, interstitium or renal vessels)
What does post-renal AKI result from?
What is obstruction of urine flow
What blood test is used to assess kidney function?
What is serum creatinine.
A patient has vomitting and diarrhoea for 3 days and develops an AKI. What type is most likely?
What is Pre-renal AKI
Name 3 causes of pre-renal AKI
What is:
Hypovolaemia
Effective volume loss (HF)
Severe hypotension
What is the most common cause of intrinsic AKI in hospitalised patients?
What is Acute tubular necrosis
Name 2 causes of post-renal AKI.
What is:
BPH
Ureteric stones
Tumours
Blood clots
What happens to serum creatinine in an AKI?
What is increases.
An elderly man develops AKI with difficulty urinating and a distended bladder. What type of AKI?
What is post-renal AKI.
Why does hypovolaemia cause AKI?
What is:
- decreased circulating volume
- decreased renal perfusion
- decreased glomerular hydrostatic pressure
- decreased GFR
What is acute tubular necrosis and what causes it?
What is ATN= tubular epithelial injury.
Caused by:
1. Ischaemia
2. Nephrotoxins
What imaging test is commonly used to look for an urinary tract obstruction?
What is Renal ultrasound
In pre-renal AKI, would you expect urine sodium to be low or high?
What is low.
Less perfusion to the kidney- RAAS activated. Na preserved in the blood, less in urine
A patient with sepsis develops hypotension followed by AKI. What mechanism could explain this?
Systemic hypotension, decreased blood flow to kidneys, ischemia of kidneys
- pre renal AKI
What would you expect to see on urine anaylsis in pre-renal AKI?
What is normal result (provided it has not progressed to ATN)
Name 2 causes of intrinsic AKI other than ATN.
What is:
1. Atheroembolism (spont or after intra-arterial manipulation)
2. Glomerulonephritis
3. Rhabdomyolysis
4. Acute Interstitial Nephritis
Why does an obstruction cause a reduction in GFR?
What is increased pressure proximal to obstruction, increased tubular/ Bowman space hydrostatic pressure, this opposes blood pressure driving filtration = lower net filtration
How can urine sediment help distinguish ATN from pre-renal AKI?
Pre-renal: bland sediment. hyaline casts
ATN: epithelial casts OR muddy brown granular casts
A patient with an AKI has haematuria and RBC casts. Is this more suggestive of pre-renal, intrinsic or post renal AKI?
Intrinsic- likely glomerulonephritis
How does the body maintain GFR during reduced renal perfusion?
What is low blood volume triggers RAAS which preferentially constricts the efferent arteriole.
This raises hydrostatic pressure to keep GFR stable despite overall lower blood volume.
After starting a new nephrotoxic drug a patient develops an AKI. What type of intrinsic AKI might have occured? Bonus: what type of drug might they have started?
What is acute tubular injury
- Chemotherapy
- Antibiotics: aminoglycosides
A patient has bilateral ureteric obstruction. Why might their creatinine rise even though the initial problem is not within the kidney tissue itself?
What is post-renal AKI causing increased back pressure and reduced GFR?
A patient with AKI has haematuria and red blood cell casts. This finding points toward injury at this location within the nephron.
What is the glomerulus.
A patient has AKI, oliguria, muddy brown casts. What is the most likely diagnosis?
ATN