Acute Kidney Injury

Question 1

What are the characteristics of nephritic syndrome?

Answer 1

• Haematuria
• Hypertension
• Oliguria (<400mL/24hrs)

Question 2

What are the complications of AKI?

Answer 2

AKI has complications associated with electrolyte levels and imbalances.

These include:

• Metabolic acidosis: lack of ability to excrete acid
• Hyperkalaemia: increased risk of AF, sodium and potassium exchanger (fall in intracellular Na will reduce Na/K/ATPase activity), hyperglycaemia causing water movement from intracellular to extracellular, and solvent drag moves potassium out of the cell.
• Hypocalcaemia and hyperphosphataemia
• Fluid overload
• Changes in mental status

Question 3

What constitutes nephritic syndrome?

Answer 3

• Haematuria
• Hypertension
• Oliguria (<400 mL/24 hours)

Question 4

What constitutes nephrotic syndrome?

Answer 4

• Proteinuria (>3.5gm)
• Hypoalbuminaemia in serum (<3gm)
• Generalised oedema
• Hyperlipidaemia and lipiduria
• MAYBE HTN

Question 5

How do you calculate GFR? (3)

Answer 5

1. 24 hour urine creatinine clearance:
   [(urine Cr) x (urine volume)] / (serum creatinine)
2. Cockcroft Gault equation
3. MDRD equation

Question 6

Where is potassium stored and what causes hyperkalaemia?

Answer 6

Potassium is stored intracellularly. It is released extracellularly by various states:

• AKI
• Metabolic acidosis
• Diabetes mellitus
• Increased osmolality (sodium) due to hyperglycaemia
• Acute cell-tissue breakdown
• Drugs
• Low catecholamines

Question 7

How is potassium reabsorbed in the tubules?

Answer 7

60-75% of potassium: 3Na+/2K+ pump is used in the proximal tubules for reabsorption.

15-20% of potassium: reabsorbed in the proximal Loop of Henle through Na+/K+/ATPase pump.

Question 8

What is the role of aldosterone in potassium hemostasis?

Answer 8

Aldosterone helps excretion of potassium via mineralocorticoid receptor in the distal tubule and collecting ducts.

Question 9

What is the role of insulin and potassium hemostasis?

Answer 9

Insulin increases potassium reuptake in the liver and muscle cells by stimulating Na+/K+/ATPase.
Large increase in extracellular [K+] lead to insulin release.

Question 10

How does metabolic acidosis cause hyperkalaemia?

Answer 10

Acidosis increases extracellular K+ levels by inducing a shift of K+ from intracellular to extracellular compartment in exchange with H+ uptake.

Question 11

What cell-tissue breakdown examples are there that can lead to hyperkalaemia?

Answer 11

Rhabdomyolysis, haemolytic anaemia.

Question 12

What are ECG changes of hyperkalaemia?

Answer 12

Peak T waves 
Shortened QT interval 
Widened QRS complex 
Sine wave 
VF

Question 13

What is treatment for hyperkalaemia?

Answer 13

1. Calcium gluconate
2. Loop diuretics
3. Insulin
4. Beta-adrenergic agonists
5. Haemodialysis
6. Treatment of hypovolemia
7. Treatment of reversible effects of hyperkalaemia