Acute kidney injury Flashcards
(34 cards)
Define AKI
An abrupt deterioration in renal function, usually over hours - days
Usually reversible
What are the hallmarks of AKI?
Falling urine output + rising creatinine and urea
Discuss RIFLE classification of AKI
Describes AKI - uniform definition
Three severity levels:
R - risk (patient is at risk of kidney damage)
I - injury (kidneys have been inured)
F - failure (kidneys have failed)
Two outcomes:
L - loss (loss of funtion)
E - end stage renal disease (end stage renal disease has developed)
What are the stages of AKI outlined by RIFLE?
- R = stage 1 (a serum creatinine rise of >26.4micromol/L or a 1.5x increase in 48hrs)
- I = stage 2 (a 2-3x increase in serum creatinine)
- F = stage 3 (a >300% increase in serum creatinine equal to >354micromol/L)
What is normal serum creatinine?
Women: 53-115 umol/L (0.5-1.0mg/dL)
Men: 88-150umol/L (0.7-1.2mg/dL)
What level of creatinine might indicate renal
>1.2mg/dL / >115umol/L
Why do men have higher creatinine levels?
Higher muscle mass generally
What are causes for increased urea, other than altered renal function?
- Corticosteroid treatment
- Tetracycline treatment
- GI bleed (blood enters gut, it is high in protein and leads to production of urea)
Outline causes of high creatinine other than renal damage
- High muscle mass
- Red meat ingestion
- Muscle damage/ rhabdomyolysis
- Decreased tubular secretion due to durgs such as cimetidine or trimethoprim)
Discuss mortality rates associated with AKI
- Uncomplicated AKI 5-10%
- AKI complicating non-renal organ failure 50-70%
Outline some causes of AKI
- Rhabdomylolysis: crush injuries, myoglobin (nephrotoxin) released, resulting in acute tubular necrosis. Can also occur in haemolysis where haemoglobin is the nephrotoxin
- Acute cortical necrosis: renal hypoperfusion causes blood to be diverted to the medulla of the kidney meaning the cortex is hypoperfused and irreversible glomerular damage occurs (cortical necrosis)
- Contrast nephropathy: in patients with impaired renal function iodinated radiological contrast media can be nephrotoxic
What is creatinine?
- Indicator of renal health
- Breakdown product of creatine phosphtae in muscle, produced at a constant rate
- Removed from the blood purely by the kidneys
- High creatinine = low GFR
What is the most accurate way to measure GFR?
- Measuring clearance of exogenous filtration markers e.g. inulin, iothalamate or iohexol
* Rarely done because it is £££ and requires strict protocol
What are the stages of AKI
Stage 1: Rise in serum creatinine >26.5mmol/L or 150-200% of baseline
Stage 2: increase of creatinine 200-300% of baseline
Stage 3: >300% increase of baseline
What are the disadvantages of using serum creatinine to measure GFR?
- Many factors affect serum creatinine
- Rises in serum creatinine take 12-24hrs to rise following surgery
Outline pre- renal causes of AKI
- Reduced perfusion (hypovolemia or haemorrhage)
- Sepsis
- Third spacing of fluid (e.g. pancreatitis, fluids leak out into peritoneal cavity thus depleting vascular fluids)
- Heart failure
- Renovascular disease
- Patients with bilateral artery stenosis that have been started on ACEi, causes ATN
Outline renal causes of AKI
- ATN
- Glomerulonephritis
- Interstitial nephritis
Outline post-renal causes of AKI
- Mechanical obstruction
- Retroperitoneal fibrosis
- Lymphoma
- Tumour
- Enlarged prostate
- Stricture
- Ascending UTI
- Urinary retention
What is the most common form of AKI?
ATN due to prolonged ischaemia
Outline some causes of ATN
- ROS
- Compliment activation
- Drugs
- Endotoxins
- Radiocontrast media
*45% of cases of AKI are caused by ATN
History associated with pre-renal AKI
Haemorrhage, vomiting, diarrhoea, sweating
Hx of sepsis, burns, GI surgery or pancreatitis
Thirst, dizziness, tachycardia, oliguria, anuria
History associated with intrinsic/ renal AKI
Usually ATN caused by:
- Severe infection, nephrotoxic drugs, major surgery
- Hx of rash, haematuria or oedema with hypertension suggestive of nephritic syndrome
- Query recent drug use and medications
Patients most likel to present with post-renal AKI
- Men with prostate enlargement
- Hx of malignancy
Discuss physical examination findings of a patient with AKI
- Hypo/ hypertension
- Asterixis
- Fluid loss? Hypotension and signs of circulatory collapse
- Glomerular disease? Hypertension, oedema, proteinuria, microscopic haematuria
- Presence of rash/ pettechiae? suggestive of glomerulonephritis
- Abdominal bruit? Renovascular disease
- Prostatic disease? Abdo distension due to full bladder
