10.4 Key Concepts in Acute Renal Failure (ARF)

Question 1

What’s the difference between Acute Renal Failure (ARF) and Acute Kidney INjury (AKI)

Answer 1

• None
• They’re the same thing

Question 2

True or false: ARF/AKI is not a single disease, but rather three subtypes of a disease

Answer 2

• False. Not a disease at all.
• Just an acute decline in GFR over days or weeks; can arise from many different causes

Question 3

True or false: standard practice is to wait until oliguria/anuria are present before diagnosing AKI/ARF.

Answer 3

• False
• These are extremely late signs; do not wait until then to suspect AKI

Question 4

Why is it challenging to distinguish between acute and chronic renal failure?

Answer 4

• If chronic, changes may have progressed too subtly for the patient to notice
• The body may have also compensated during the earlier stages of chronic failure, making it harder for the patient to detect

Question 5

Why is it important to distinguish between acute and chronic renal failure?

Answer 5

• Acute may be reversible, chronic less likely reversible
• Affects possibly underlying causes/treatment planning

Question 6

True or false: pre/post/renal categorisation of AKI is one of the oldest and most well-defined categorisation systems in physiology. This is due to the early discovery of prostate hypertrophy.

Answer 6

• False
• There can be lots of overlap between the categories

Question 7

Define pre-renal, renal, and post-renal kidney failure, and give a few examples of each

Answer 7

1. Pre-renal, due to inadequate kidney perfusion. Typically reversible if perfusion is restored. (hypovolaemia, renal artery stenosis)
2. Renal, involving direct damage to the kidneys themselves (acute tubular necrosis, acute interstitial nephritis, rhabdo etc.)
3. Post-renal, caused by dusfynction distal to the kidneys (e.g. neurogenic bladder, ureteral obstruction, posterior urethral valves etc.)

Question 8

What information should we use to help determine the underlying cause of ARF/AKI?

Answer 8

• Patient history/collateral if uraemia renders unable to respond
• Exam findings
• Disease progression; is this acute or chronic? (recall some reasons why this might be difficult to determine)

Question 9

List 4 metabolic/ionic imbalances that can occur as a result of renal failure, and why

Answer 9

1. Hyperkalaemia (kidneys can’t filter out potassium)
2. Uraemia (waste products like urea and creatiine are backed up, since kidneys aren’t clearing them like normal)
3. Severe fluid overload (urine production is lowered since kidneys are fucked, meaning more fluid is retained in the body)
4. Severe acute metabolic acidosis (kidneys can’t clear acid, do pH increases. This can lead to resp compensation [kussmaul breathing] like in DKA)