Acute Kidney Injury (AKI)

Question 1

What is AKI?

Answer 1

Abrupt decline in kidney function (days to hours)
characterised by high serum creatinine + urea and low urine output

Question 2

What is the classification that used to be used for staging and what is the new one?

Answer 2

Used to be RIFLE
Now is AKIN/KDIGO

Question 3

What does RIFLE stand for?

Answer 3

Risk
Injury
Failure
Loss of function
End stage Kidney disease

Question 4

What are the classification categories for AKI in KDIGO?

Answer 4

Serum creatinine increased by 26 micromol/L within 48hrs
or
1.5 x baseline in 7 days
or
Urine output <0.5ml/kg/hr for 6-12 hrs

Question 5

What are the 3 causes of AKI?

Answer 5

Pre renal
Intra renal
Post renal

Question 6

What are pre renal causes?

Answer 6

Hypoperfusion

Volume depletion = haemorrhage , GI loss, renal loss, hypovolemia

Decreased CO = MI, HF, Cardiogenic shock

Vasodilation = anaphylaxis, sepsis

Blood supply issue = Aortic dissection, renal artery blockage/stenosis

Drugs - NSAIDS, ACE-i, IV contrast, anaesthetic

Question 7

What are the intra renal causes?

Answer 7

Nephron + parenchymal damage

Tubular - MC = Acute tubular necrosis (kidney tubules die)

Interstitial (made of fever, rash, eosinophilia) = acute interstitial nephritis

Glomerular - Px often with glomerulonephritis

Toxins = sepsis

Question 8

What is a Sx seen in Tubular necrosis?

Answer 8

Muddy brown casts in urine - dead tubular cells

Question 9

What are the post renal causes?

Answer 9

Obstruction of urinary flow

Stones in urethra/bladder/ureter
BPH - common in old men
(Drugs - anti cholinergics, CCB)

Question 10

What are the top 3 causes of AKI?

Answer 10

Sepsis
Cardiogenic shock
Surgery

Question 11

Rf for AKI?

Answer 11

Increased age
Comorbidities (htn, T2DM, congestive HF)
Hypovolemia of any cause
Nephrotoxic drugs

Question 12

Pathology of AKI?

Answer 12

Decreased blood filtration + urine output therefore accumulation of (usually excreted) substances

Question 13

Which substances are usually excreted and what happens to them?

Answer 13

KUFH

K+ = hyperkalemia = cause arrhythmias

Urea = hyperuremia = cause pruritus (urea deposits in skin), uremic frost, confusion if severe)

Fluid - oedema

H+ = Acidosis

Question 14

What Sx are presented as a result of uremia?

Answer 14

Encephalopathy (confusion links to HE in liver failure as ammonia is a byproduct of urea metabolism)

Pericarditis

Skin manifestations

Question 15

What Sx are presented as a result of Fluid overload?

Answer 15

Oedema (or hypovolemic shock, if pre renal cause oliguria / Anuria (little to no urine output) + palpable bladder

Question 16

What Sx are presented as a result of high H+ ?

Answer 16

Metabolic acidosis

Question 17

What Sx are presented as a result of hyperkalemia?

Answer 17

Arrhythmias (+ haematuria + proteinuria)
ECG =
Go (P waves flat)
Go tall (Tall tented T waves)
Go Long (prolonged PR interval)
Go wide (Wide QRS)

Question 18

Dx?

Answer 18

Establish cause (pre/intra/post) + diagnose with KDIGO classification (serum creatinine and urine output)

FBC + CRP to check for infection
U+E to check H+, K+, urea and creatinine

Question 19

Best ways to diagnose pre/intra/post renal?

Answer 19

pre:
Urea:Creatinine
if U:Cr = >100:1 pre renal
<40:1 renal
40-100:1 = post renal

Intra:
renal biopsy (cause)

Post:
USS

Question 20

Tx of AKI?

Answer 20

Treat complications:
Hyper K+ = cardiac changes = IV calcium gluconate (stabilises cardiac membrane) + insulin + dextrose
No cardiac changes = insulin + dextrose

Metabolic acidosis = sodium bicarbonate

Fluid overload = diuretics

Tx underlying cause (pre/intra/post)

Question 21

What Tx is last resort?
Indicated in?

Answer 21

RRT (renal replacement therapy)
Haemodialysis; indicated in:
Acidosis (pH <7.1)
Fluid overload (oedema pul)
Uremia (Sx)
K+ > 6.5 / ECG changes