8.15 Acute Renal Failure

Question 1

What is the best marker for kidney function?

Answer 1

Creatinine (muscle fuel)
Look at glomerular filtration rate (GFR)

Question 2

What is normal creatinie?

Answer 2

M: 80-100
F: 60-80

Question 3

What to do if creatine is high in pt?

Answer 3

• ANY increase in creatine is NB!!

Question 4

Acute renal failure

Answer 4

• abrupt decline in renal function
• rise in urea & creatinine
• reversible
• mortality: 20% overall (acute insult to kidney) 50% ICU

Question 5

Acute vs. Chronic

Answer 5

• previous creatinine levels (if previously ⬆️ = chronic)
• kidney size (Ultrasound)
• kidney biopsy (when don’t know what caused it) chronic = show sclerosis

Question 6

NB Etiology of ARF (Acute renal failure)

Answer 6

1. Prerenal 75%
- lack of perfusion (bloodflow)
- tubular necrosis

2. Renal of kidney itself
- bloodvessels
- glomerulus
- tubules (ATN)
- interstitium

3. Postrenal
- obstruction

Question 7

Prerenal failure

Answer 7

• nothing wrong with kidney
• not being profused (Blood flow low or low BP)
• ischemia is driver
• progession leads to tubular necrosis

Question 8

Renal causes of ARF

Answer 8

• bloodvessels
• glomerulus
• tubules
• interstitial

Slide 9

Question 9

Postrenal failure

Answer 9

• diagnosis by ultrasound
• Renal failure if both kidneys obstructed
• prostate
• bladder
• stones
• PUJ stenosis (post urethral valves)

Question 10

Causes of reduced renal bloodflow

Answer 10

• true hypovolaemia (bloodloss, dehydra)
• ⬇️ effective circulatory volume or pressure (cardiac; systemic vasodilation)
• intrarenal vasoconstriction (ACE inhibitors / NSAID’s)

Question 11

What happens if bloodflow is reduced to kidneys?

Answer 11

Fall in GFR
- ⬇️ urine output
- ⬆️⬆️ urea
- ⬆️ creatinine

Activation of renin-AT-aldosterone
- retention of Na+ (& water) -> concentraed urine

KIDNEYS ARE NORMAL AND RESPOND APPROPRIATELY TO REDUCED PERFUSION

Question 12

Pathogenesis of Acute Tubular Necrosis (ATN)

Answer 12

• Ischaemic (⬇️ renal perfusion)
• nephrotoxic (endogenous, exogenous toxin)

Question 13

What part of kidneys can regenerate and which can’t?

Answer 13

Tubules = can
Glomerulus = can’t

Question 14

Nephrotoxic ATN

Answer 14

Mechanisms
- vasoconstriction
- direct tubular toxicity
- tubular obstruction

Drug induced
- NSAID’s
- Radiocosides
- Aminoglycosides

Endogenous toxin
- Myoglobin (muscle necrosis)
- Haemoglobin (haemolysis)
- AL light chains (myeloma)

Question 15

Prerenal vs. ATN

Answer 15

Prerenal
- normal kidney that hand on to Na+ and urea
- urine normal
- serum urea:creat 1:10
- good response to saline

ATN
- damaged tubules unable to concentrate or hold back Na+
- proteinuria / haematuria / casts
- serum urea:creat 1:20