11 - Renal function

Question 1

Which arteriole connected to renal function is larger?

Answer 1

The afferent

Question 2

Renal function

Answer 2

kidneys filter blood of normal unwanted byproducts

Question 3

What arteriole takes blood to the renal?

Answer 3

Afferent arteriole

Question 4

What arteriole takes blood away from the renal?

Answer 4

efferent arteriole

Question 5

What are the 4 steps that occur within the renal?

Answer 5

1. Filtration
2. Reabsorption
3. secretion
4. excretion

Question 6

glomerular Filtration Rate (GFR)

Answer 6

Glomerular Filtration Rate (GFR) is the best overall index of kidney function, and while we want to measure it we may have to satisfy ourselves with estimating it (eGFR).
Renal failure is used to mean the failure of the primary function of the kidney – that is excretion.

Question 7

What if the GFR falls ?

Answer 7

• A fall in GFR results in reduced excretion of urea and creatinine
– Elevated serum urea (uraemia)
– Elevated serum creatinine

Question 8

What problem may it be if the GFR falls?

Answer 8

– Prerenal (Hypotension),
– Renal (Glomerulernephritis), or,
– Postrenal (Obstruction)

Question 9

What processes of impacted when GFR falls?

Answer 9

• Erythropoietin production
• Vitamin D production
• Regulation of acid-base balance
• Regulation of salt-base balance
• Regulation of blood pressure

Question 10

Ideal test of glomerular function

Answer 10

The ideal test:
• Accurately reflects GFR
• Detects changes in GFR i.e. decline in function
• Easy to use in clinical practice
• The use of inulin is common – used because it is neither secreted or absorbed by the kidney.
• However it is not easy to use.

Question 11

Creatinine clearance

Answer 11

creatinine excreted = Urine Cr x Vol
CrCl ml/min = ——————————- ————————
time Plasma Cr x time

Question 12

Creatinine clearance issues

Answer 12

• Collection of urine
• Detects changes in GFR i.e. decline in function
• Not easy to use in clinical practice

Question 13

What equation is used to estimate GFR?

Answer 13

MDRD equation as it only requires a sample of blood to be collected

Question 14

What correctional values are used for MDRD?

Answer 14

What correctional values are used for MDRD?

Question 15

What happens when you plot GFR vs MDRD?

Answer 15

If it was a perfect agreement between the measures all points would be on a diagonal line but is useful to establish GFR in disease when GFR is low

Question 16

Renal function and CKD

Answer 16

Reduced eGFR, and hence reduced kidney function is associated with early death.