Kidney function and NPNs

Question 1

Main functions of the kidneys:

Answer 1

1. Excretory function - remove unwanted waste product and excess water
2. Regulatory function - regulation of fluid and acid-base balance; conservation of nutrients
3. Endocrine function - ADH and aldosterone

Question 2

Basic process in urine formation: filtration, reabsorption, secretion:

Answer 2

Filtration: only small (can be any charge) and larger (+ve/neutral) molecules pass by hydrostatic pressure.

Reabsorption: most filtered elements are reabsorbed. prevents loss of water

Secretion: removal of further waste products, regulate acid-base balance

ADH: water
Aldosterone: water and NaCl

Question 3

Main causes of kidney disease:

Answer 3

1. Disruption of blood flow (low filtration, low GFR)
2. Disruption of urine flow
3. Nephron damage

Question 4

Other name for glomerulonephritis:

Answer 4

Acute nephritic syndrome

Question 5

What disease have an increase in glomerular permeability:

Answer 5

Nephrotic syndrome

Question 6

What does nephrotic syndrome entails?

Answer 6

Passage of molecules like proteins to pass (esp. albumin) resulting in proteinuria, low albumin in plasma, lipiduria. Big molecules are NOT passing.

Question 7

What does acute nephritic syndrome entails?

Answer 7

Altered permeability and decreased filtration allowing bigger molecules to pass through like cells and proteins. They accumulate in blood (low filtration) and can result in hematuria, proteinuria, pyuria.

Question 8

Where within the nephron is electrolyte and water reabsorption controlled by aldosterone and ADH?

Answer 8

DCT and collecting duct

Question 9

What effect would hyperproteinemia likely have on filtration (increase or decrease) and why?

Answer 9

Decreased; high proteins in capillaries, will want to keep fluid to equalize osmotic pressure .

Question 10

Other causes for kidney disease:

Answer 10

Tubular disease
Interstitial disease
Vascular disease (less blood flow)

Question 11

What would constitute a good component for a clearance test?

Answer 11

1. Not reabsorbed
2. Freely filtered
3. Not secreted

Question 12

Principle of Jaffe reaction:

Answer 12

creatinine + picric acid (in alkaline) = color

Question 13

Interferences for Jaffe reaction and what can be done to be corrected:

Answer 13

Hemolysis: RBC release substance which reacts with rgt
Bilirubin: false neg; interfere with rgt
Bacteria: false neg; slows down reaction

Kinetic reaction is used: rate of change in abs in measured btw a certain window of time.

Question 14

Rules for specimens collection for creatinine:

Answer 14

No ammonium (no NH anticoagulants)
Separate cells (RBC and ammonia production)

Question 15

What are NPNS?

Answer 15

Non-protein nitrogenous compounds - good indicator for renal function

Question 16

Why pre-renal, renal and post-renal conditions associated with high blood creatinine/urea/uric acid?

Answer 16

Pre-renal: decreased blood flow and filtration (low GFR) = increase in blood

Renal: kidney disease = less filtration

Post-renal: urinary obstruction, increased reab

Question 17

Urea is the breakdown of

Answer 17

Protein

Question 18

What can cause a low urea to creatinine ratio?

Answer 18

Decreased GFR, high reab = more in blood
Low protein intake (decrease in urea, not creat)
Severe liver disease
Starvation

Question 19

What can cause a high urea to creatinine ratio with normal creatinine?

Answer 19

high urea/N creatinine

Increased protein breakdown (more urea)
Increased protein intake

Question 20

What can cause a high urea to creatinine ration with high creatinine?

Answer 20

Decreased GFR with increased reabsorption of urea (very high urea with high cret due to low GFR) = hypoperfusion

Question 21

Uric acid is a breakdown of:

Answer 21

Nucleic acid and purines

Question 22

Main concern with high uric acid?

Answer 22

Gout: insoluble deposition of urate = crystals

Question 23

Specimen rules for urea collection

Answer 23

No fluoride (inhibits urease)
No ammonium

Question 24

Principle of uric acid:

Answer 24

Uric acid broken down by uricase gives H2O2. Then Trinder’s reaction

Question 25

Specimen rules for uric acid collection

Answer 25

No fluoride or EDTA

Question 26

Interferences for Trinder’s

Answer 26

Reducing substances (ascorbic acid) : compete with chromogen (false low)
Oxidizing substances: oxidize with chromogen (can change its color) (false high)

Question 27

Specimen rules for ammonia collection

Answer 27

PLASMA
Minimize contact with air
Transport on ice
No contact with smocking or exogenous ammonia
Separate quickly (RBC have ammonia)
Bacteria

Question 28

What happens in MAU?

Answer 28

Levelled increased but not detectable by routine testing. Indicate increased permeability which reflect indicator for kidney dmg.

Question 29

What urine specimen is preferred for MAU

and why?

Answer 29

24h random (or timed)

Creatinine and albumin are measured for albumin to creatinine ratio where it compensates for urine concentration in the day.