Acute Kidney Injury

Question 1

What is the rough definition of AKI and the different stages?

Answer 1

It is the decline of renal excretory function over hours/days with a rise in serum urea and creatinine.
Stage 1- Creatinine raised by 1.5-1.9 of baseline or urine output <0.5ml/kg/hr for 6 hours.
Stage 2 - Serum creatinine 2x the baseline or urine output <0.5ml/kg/hr for24 hours.
Stage 3 - Serum creatine 3x the baseline or creatinine >354 or or urine output <0.3ml/kg/hr for 24 hours.

Question 2

What is oliguria?

Answer 2

Infants - Less than 1mL/kg/hour
Adults - Less than 0.5mL/kg/hour.
Roughly less than 400-500ml per 24 hours

Question 3

What are the causes of an AKI?

Answer 3

Prerenal,
Renal
Post renal

Question 4

What are the pre renal causes of an aki?

Answer 4

Hypovolaemia and hypotension (could be due to diarrhoea/vomiting, inadequate fluid intake, blood loss)
Reduced effective circulatory volume (cardiac failure or sepsis)
Drugs such as ACEi or NSAIDs.
Renal artery stenosis

Question 5

What are the renal causes of an AKI?

Answer 5

Glomerular, interstitial, vascular or tubular.
1. Glomerulonephritis,
2. Acute tubular necrosis,
3. Acute intertitial nephritis
4. Rhabdomyolysis,
5. Tumour lysis syndrome,
5. Vasculitis

Question 6

What are the post renal casues of an AKI?

Answer 6

Obstruction eg, kidney stones in ureter, BPH, external compression of the ureter

Question 7

What is acute tubular necrosis?

Answer 7

Necrosis of tubular epithelial cells - reversible

Question 8

What are the causes of acute tubular necrosis?

Answer 8

Ischaemia: shock or sepsis.
Nephrotoxins: Aminoglycosides, myoglobin, NSAIDs, radiocontrast agents and lead

Question 9

What are the features of acute tubular necrosis?

Answer 9

AKI and muddy brown casts in the urine

Question 10

What are the cause’s of acute interstitial nephritis?

Answer 10

Drugs: Penicillin, rifampicin, NSAIDs, allopurinol, furosemide.
Systemic disease: SLE, sarcoidosis, Sjogren’s syndrome.
Infection: Hanta virus, staphylococci

Question 11

What are the features of acute interstitial nephritis?

Answer 11

Fever, rash, arthralgia,
Eosinophilia,
Mild renal impairment,
Hypertension

Question 12

What are the investigations for acute interstitial nephritis?

Answer 12

Sterile pyuria and white cell casts

Question 13

What are some risk factors for development on an AKI?

Answer 13

CKD,
Organ failure/chronic disease,
History of AKI,
Nephrotoic drugs,
Iodinated contrast,
age > 65 years old,
oliguira

Question 14

What are the signs and symptoms of an AKI?

Answer 14

Reduced urine output,
Pulmonary and peripheral oedema,
Arrythmias secondary to changes in potassium.
Features of uraemia

Question 15

What are the investigations for an AKI?

Answer 15

U&Es
Urinalysis,
ABG- look for acidosis
ECG to look for hyperkalaemia changes
Imaging - Renal ultrasound if unknown cause or at risk of obstruction

Question 16

What drugs are usually safe to continue in AKI?

Answer 16

• Paracetamol
• Warfarin
• Statins
• Aspirin (at a cardioprotective dose of 75mg od)
• Clopidogrel
• Beta-blockers

Question 17

What drugs should be stopped in an AKI?

Answer 17

• NSAIDs (except if aspirin at cardiac dose e.g. 75mg od)
• Aminoglycosides
• ACE inhibitors
• Angiotensin II receptor antagonists
• Diuretics

Question 18

What drugs might have to be stopped in an AKI?

Answer 18

Metformin,
Lithium,
Digoxin

Question 19

What is the management of hyperkalaemia?

Answer 19

Anyone with potassium > 6.5 or with ECG changes should give IV calcium gluconate and insulin/dextrose infusion.
Further management: Stop exacerbating drugs (ACEi), lower body potassium with calcium resonium, loop diuretics or dialysis

Question 20

What is the diagnostic criteria for an AKI?

Answer 20

1. Rise in creatinine of 26+ in 48 hours.
2. 50% plus rise in creatinine over 7 days.
3. Fall in urine output to below 0.5ml/kg/hour for more than 6 hours

Question 21

What patient’s with an AKI should be referred to a nephrologist?

Answer 21

Stage 3 AKI
Renal transplant,
ITU patients with unknown cause of AKI,
Vasculitis/glomerulonephritis/myeloma etc,
AKI with no known cause,
Inadequate response to treatment,

Question 22

How can you differentiate between AKI and CKD?

Answer 22

Renal US. CKD will almost always have small kidneys (normal is 10-13cm)except for: AD polycystic kidney disease, diabetic nephropathy, amyloidosis, HIV associated nephropathy.
Or if patient is hypocalcaemia (suggests CKD)

Question 23

What are the indications for acute dialysis?

Answer 23

Acidosis
Electrolyte imbalance (resistant hyperkalaemia),
Intoxication (drug overdose),
Oedema (refractory pulmonary oedema)
Uraemia (encephalopathy or pericarditis)

Question 24

What is the managements of an AKI?

Answer 24

A-E exam.
Address immediate threats eg, acidosis, hypovolaemia, hyperkalaemia, sepsis.
Identify and treat underlying cause.
Supportive management: IV fluids, stop nephrotoxic drugs and relieve obstruction via catheter.
Monitor patient.
Review medications

Question 25

Which patient’s with an AKI should be admitted to hospital?

Answer 25

stage 3 AKI,
No identifiable cause,
Obstructed or infected AKI,
Sepsis.
Evidence of hypovolaemia or need for IV fluids

Question 26

What are the effects of giving a statin and a macrolide?

Answer 26

Increases level of statins which can cause rhabdomyolysis - AKI

Question 27

What is involved in a GN screen?

Answer 27

ANA, ANCA, C3/4, anti-gbm, rh factor