Kidney Diseases: The Basics

Question 1

What are the functions of the kidney? [6]

Answer 1

1. Metabolic waste excretion
2. Endocrine functions
3. Drug metabolism/excretion
4. Control of solutes and fluid status
5. Blood pressure control
6. Acid/base regulation

Question 2

How do you measure kidney function?

1. how to measure waste excretion? [2]
2. how to measure endocrine function? [3]
3. how to measure control of solutes and fluid status? [3]

Answer 2

1. urea & creatinine
2. vitamin D, EPO, PTH
3. sodium, potassium, fluid

Question 3

What is the glomerular filtration barrier composed of histologically? [2]

Answer 3

1. fenestrated capillary endothelium
2. podocyte foot processes

Question 4

How is glomerular filtration rate controlled? [7]

Answer 4

1. blood flow
   
   • angiotensin II - efferent arteriole vasoconstriction
   • myogenic control
   • sympathetic nervous system - afferent arteriole vasoconstriction
   • reduced blood volume due to baroreceptors (SNS), renin (ADH), and angiotensin II
2. intraglomerular pressure
3. transmembrane pressure - filtration barrier
4. oncotic pressure

Question 5

List the eGFR categories from G1 (normal or high) to G5 (kidney failure) [6]

Answer 5

• G1 = normal or high: >90ml/min/1.7m²
• G2 = mildly decreased: 60-89ml/min/1.7m²​
• G3a = mildly-moderately decreased: 45-59ml/min/1.7m²​
• G3b = moderately-severely decreased: 30-44ml/min/1.7m²​
• G4 = severely decreased: 15-29ml/min/1.7m²​
• G5 = kidney failure: <15ml/min/1.7m²​

Question 6

Creatinine

1. what is it? [1]
2. its concentration is affected by what? [1]
3. how much (%) is secreted by tubule? [1]

Answer 6

1. breakdown product of muscle
2. concentration affected by plasma volume
3. up to 15% secreted by tubule

Question 7

What is renal clearance? [1]

Answer 7

volume of plasma which would be cleared of the substance per unit of time