lab Diagnosis lecture - renal tests

Question 1

what does renal function testing tell us?

Answer 1

renal blood flow, GFR, and tubular function

Question 2

what does renal disease imply

Answer 2

presence of histological leasions in kidney, not degreee of dysfunction

Question 3

renal failure

Answer 3

75% of total nephron pop is non functional, not necessarily histological lesiona, could be dehydration

Question 4

what are the two main categories of renal testing

Answer 4

1. to evaluate clearance, 2. evaluate tubular function

Question 5

What 4 tests are to evaluate clearance?

Answer 5

Blood urea nitrogen(BUN), Serum Creatinine, Creatinine clearance , Albumin creatine ratio

Question 6

what are the tests to evaluate tubular function?

Answer 6

fractional excretion of NA+

Question 7

What is GFR

Answer 7

measure of volume of plasma from which a substance is removed by glomerulus

Question 8

what is the most frequently preformed renal function test

Answer 8

GFR

Question 9

what is importaint in substance to measure GFR

Answer 9

1.filtered through Glom, 2.non protein bound, 3.not used in body, 4.only way out is kidneys, 5.doesn’t do anything at renal tubules, 6. stable in blood and urin, 7. easily measured

Question 10

What does blood nitorgen come from

Answer 10

protein catabolism

Question 11

What makes the BUN not accurate without calculations in urine?

Answer 11

100% is filtered by the glomerulus, then 40% is reabsorbed by tubules, so your clearance is only 60% of actual

Question 12

What is serum plasma testing for?

Answer 12

evaluate liver function, rough indicator of GFR and renal blood flow althoug its indirect

Question 13

serum plasma testing is part of what pannel

Answer 13

CMP comprehensive metabolic pannel or basic metabolic pannel, BMP

Question 14

what can decreas BUN levels

Answer 14

pregnancy and liver disease, malnutrion, overhydration

Question 15

asotemia

Answer 15

increased blood urea nitrogen

Question 16

Prerenal causes of Bun increase, azotemia

Answer 16

Low blood volume, CHF, MI, GI bleed, High protein, Starvation, Sepsis

Question 17

Renal causes of azotemia, BUN increase

Answer 17

Renal disease, glomerulonephritis, pyelonephritis, tubular necrosis, drugs

Question 18

Post renal causes of azotemia, Bun increase

Answer 18

Ureter obstruction, bladder outlet obstruction (prostate)

Question 19

What is a more stable marker than BUN?

Answer 19

Serum creatinine, a catabolic product of creatine phosphate from skeletal muscles.

Question 20

Does BUN or Creatinine increase first?

Answer 20

BUN increases first, then serum creatinine

Question 21

why would old and young have decreased creatinine

Answer 21

reduced muscle mass.

Question 22

How much creatinine is filtered by kidneys

Answer 22

almost completely filtered by glom and secreated at proximal tubule

Question 23

what is serum creatinine used to diagnose?

Answer 23

imparied renal function because its not as affected by liver function as BUN

Question 24

what is importaint to remember about how renal disease effects BUN and creatinin

Answer 24

large changes in GFR early in disease don’t change it much, only at the late stages of renal disease do changes big enough for thiese tests to pick up happen. So it only picks up later stage renal disease.

Question 25

when taking the bun/creatine ratio, how would you know if the problem base prerenal increase(azotemia)

Answer 25

If the amount of BUN is 20 or more times that of Creatinine

Question 26

if the RUN /creatinine ratio is 10-20 :1, what does that indicate?

Answer 26

Renal Azotemia- chronic kidney disease, glomerular damage, tubular necrosis

Question 27

With what azotemia would you be able to pick up on dip stick?

Answer 27

Protein in urine during Renal axotemia

Question 28

what happens as GFR goes down?

Answer 28

serum creatine goes up

Question 29

eGFR

Answer 29

estimated GFR calculated using serum creatine

Question 30

what would make eGRF inacurate

Answer 30

Vegetarian, malmurished, old or young,

Question 31

when you need a more accurate estimate of GFR use what?

Answer 31

creatinine clearance

Question 32

How doe you get creatinine clearance

Answer 32

24 hour urine collection and blood draw that are analyzed for creatine then calculated by using patients height and weight

Question 33

does creatine clearace over or underestimate GFR?

Answer 33

Overestimates GFR by 10% due to tubular secreation.

Question 34

at what point will the GFR from CC, creatinine clearance be invalid?

Answer 34

when the GFR is less than 30% of normal

Question 35

what happens to CC as you age

Answer 35

decrease 6.5 ml/min each decade after 20.

Question 36

what can increase CC?

Answer 36

exercise, pregnancy and drugs, low if incompelte urine

Question 37

What test is superior to serum creatine?

Answer 37

cystatin C, estimates GFR independent of age, musclemass and liver damage

Question 38

how will tests tell me its acute renal failure

Answer 38

occurs over hours/days, no broad casts in urine sedament, absent anemia, kidney size, renal function hx seen normal

Question 39

how will tests tell me its chronic renal failure?

Answer 39

gradual over time, increased BUN and creatinine, small kidney, anemia present, broad casts in urine

Question 40

what is the most common cause of acute renal failure

Answer 40

pre renal and tubular necrosis

Question 41

how would you determine the difference between pre, and renal acute renal failure?

Answer 41

Fractional socium excretion

Question 42

if its Pre renal, sodium does what

Answer 42

FEN is 1%

Question 43

if its renal Acute failure FEN is what?

Answer 43

FEN is greater than 2%