Biochemistry

Question 1

What are the functions of the kidney?

Answer 1

Excretion of metabolic waste products
Homeostasis of water and electrolytes
Synthesis of: renin, 1,25 (OH)2 vit D, erythropoietin
Removal of drugs and toxins

Question 2

Definition of eGFR and what does it depend on?

Answer 2

The quantity of glomerular filtrate formed each minute in all nephrons of both kidneys.
Depends on:
Number of functioning nephrons
Glomerular function
Intracapillary pressure
Tubular lumen pressure

Question 3

What are two methods of measuring glomerular function, what are they dependant on and which is superior?

Answer 3

Creatinine (skeletal muscle)
Urea (protein)

Dependent on production and excretion. If production is constant and excretion is entirely by glomerular filtration then raised levels indicate glomerular dysfunction.

Creatinine is superior test as it is much more consistent compared to urea.

Question 4

What is normal eGFR?

What does the eGFR have to be for a diagnosis of established kidney disease?

Answer 4

Normal is 100

Established kidney disease is 30

Question 5

What is acute kidney injury?

How is it staged?

Answer 5

Any chemical, toxic, ischaemic or physical insult which results in a rise in creatinine or fall in urine output over a timescale of hours to days.

Staged 1,2,3. Increases mortality

Question 6

What are the pre-renal causes of AKI?

Answer 6

Hypovolaemia from haemorrhage or sepsis

Pump failure

Question 7

What are the renal causes of AKI?

Answer 7

Ischaemia
Nephrotoxins - drugs, paraproteins, myoglobin, poisons, metals
Glomerulonephritis
Interstitial nephritis

Question 8

What are the post-renal causes of AKI?

Answer 8

Stones
Tumor
Prostate

Question 9

What are the clinical and biochemical features of AKI?

Answer 9

Retaining nitrogenous waste products (nausea, confusion, malaise)
Fluid Overload (cardiac failure, oedema)
Retaining K+ (life threatening when >8mmol)
Retain acidic products of metabolism (life threatening when pH <7