Lecture 2 - Renal

Question 1

What is the glomerular filtration rate (GFR)?

Answer 1

Rate fluid moves from plasma to glomerular filtrate

Question 2

What are the two main factors that determine whether or not the substance is filtered?

Answer 2

1. Molecular size - molecular mass ~ 68 is threshold

2. Electrical charge = positively + electrically neutral substances pass through better than negatively charged

Question 3

What are the four main plasma electrolytes that are net excreted?

Answer 3

Urea, Creatinine, PO4, K+

Question 4

What are the two main factors that affect the GFR?

Answer 4

1. Blood volume (dehydration) and cardiac output (pre-renal factors)
2. Number of functional glomeruli = renal function

Question 5

What is diminished renal reserve?

Answer 5

> 50% percent of functional nephrons

Question 6

What is renal insufficiency?

Answer 6

25 - 50% of functional nephrons

Question 7

What is renal failure?

Answer 7

less than 25% functional nephrons

Question 8

Briefly explain how plasma clearance can be used to assess GFR (glomerular filtration rate):

Answer 8

Plasma clearance technique: plasma which is completely cleared of the substance during a time period -

Repeated blood samples over a period of several hours following IV administration

Exogenous markers: creatinine and iohexol

Question 9

How does hypovolaemic blood flow influence increase urea urea absorption in the proximal tubule?

Answer 9

60-65% is reabsorbed in proximal tubule - process is enhanced in hypovolaemic states with decreased urine flow rate = more time for passive urea absorption

Question 10

What is the name for increased urea and creatinine?

Answer 10

azotemia

Question 11

Where is creatinine produced?

Answer 11

Mainly contained in skeletal muscles - product of spontaneous, irreversible, non-enzymatic processes

Question 12

What makes creatinine a good marker of endogenous GFR?

Answer 12

• Freely filtered at glomerulus - appears in filtrate @ same concentration as in plasma
• Creatinine is not re-absorbed
• Creatinine - weakly secreted in renal proximal tubules - especially in males = negligible significance

Question 13

What can SDMA be used to indicate?

Answer 13

SDMA = symmetric dimethylarginine is produced as a byproduct of intracellular protein methylation and released into circulation after proteolysis

Question 14

Is SDMA a good prognostic marker?

Answer 14

Similar between survivors and non survivors in dogs with AKI and CKD = poor prognostic marker

Question 15

Compare the sensitivity of SDMA versus that serum creatinine:

Answer 15

SDMA sensitivity is far greater than serum creatinine