Chemistry - Cp Compendium And Osler - Renal Function

Front 1

How is urea measured?

Back 1

By the measurement of urea nitrogen

Front 2

Why does BUN slightly underestimate GFR?

Back 2

Because urea is partially reabsorbed by the nephron

Front 3

What is azotemia?

Back 3

An increase in BUN

Front 4

How do you calculate GFR based on creatinine clearance?

Back 4

Front 5

Under what circumstances can the MDRD equation be used?

Back 5

Caucausian and AA with GFR <60 between the ages of 18 and 70

Front 6

What variables make up the MDRD equation?

Back 6

serum creatinine, patent age,sex, race

Front 7

What is the normal BUN/Creatinine ratio?

Back 7

10:1

Front 8

An elevated BUN/creatinine ratio suggests what?

Back 8

Prerenal or post renal azotemia

Front 9

A decreased BUN/creatinine ratio suggests what?

Back 9

Rare. suggests dietary protein insufficiency or severe liver disease.

Front 10

What is cystatin C?

Back 10

A cysteine protease inhibitor produced by nearly all cells in the body that has been demonstrated to be better than creatinine for estimating the GFR. But, there is high within person variation compared to creatinine. Freely filtered and reabsorbed.

Front 11

What is the range of normal proteinurea?

Back 11

Does not exceed 150 mg/day

Front 12

What is the definition of significant proteinurea

Back 12

>300 mg/day on 24 hour urine collection

Front 13

What two assays can be used to detect tubular dysfunction?

Back 13

B2 microglobulin and lysozyme.

Front 14

How do you define chronic kidney disease?

Back 14

GFR < 60 ml per minute per 1.73 m2 of body surface rea or albuminuria for 3 or more consecutive months

Front 15

BUN/Cr ratio in pre-renal vs renal ARF?

Back 15

>20:1, <20:1 renal

Front 16

Urine specific gravity in prerenal versus renal ARF

Back 16

Prerenal - high >1.020
Renal - low <1.010

Front 17

Urine osmolarity in prerenal vs renal ARF

Back 17

prerenal - high - >500mmol/kg
renal - low < 300-500

Front 18

FENa in prerenal vs renal ARF

Back 18

prerenal - <35%
Renal >35%

Front 19

what is the relationship between GFR and creatinine?

Back 19

Every time the GFR falls by half, the creatinine doubles. Inverse relationship.

Because of this, early in disease, a small change in creatine when we have a decrease in GFR. Later in disease, there is a bigger change in GFR!

Front 20

how do we measure creatinine?

Back 20

Jaffe reaction: reduction of alkaline picrate (colorametric reaction), cross reacts with glucose, ketones, and cephalosporins.

An enzymatic reaction would have less interferences.

Front 21

How can we convert BUN to urea and vice versa?

Back 21

BUN (mg/dL) / 3 = urea (mmol/L) in different units!

BUN x 2.14 = urea in same units!

How to remember? Urea has 2 nitrogens. So, you multiply BUN by two to keep it in same units

BUN has 3 letters. So, divide BUN by 3 to get urea in mmol/L

Front 22

When is BUN/Creat ratio low?

Back 22

dialysis (urea is smaller so better removed than creatinine), cirrhosis, malnutrition (decreased urea production), rhabdomyolysis (increased creatinine release)

Front 23

when is BUN/Creat ratio high?

Back 23

prerenal azotemia (dehydration), acute obstruction, nephrotic syndrome, protein loads (upper GI bleed and burns)

Front 24

When would a urine dipstick be negative even though the patient has a lot of protein in the urine?

Back 24

bence jones protein

Front 25

what is microalbumin?

Back 25

small amounts of albumin detected by immunoassays. Early test for glomerular dysfunction.

Front 26

with tubular injury, what proteins do we find in urine and why?

Back 26

alpha 1 microglobulin, beta 2 microglobulin, amylase, cystatin

we find these because they are normally filtered, but aren't being reabsorbed like they usually would

Front 27

what bands do we see for glomerular damage?

Back 27

only see the smallest proteins. Albumin, alpha 1 and transferrin. (transferrin is in beta band). If a bit more damage, start to see immunoglobulins.

Front 28

what bands do we see for tubular injury?

Back 28

there is a band between alpha 1 and albumin called alpha 1 globulin. There is also a double band in alpha 2.

Front 29

what bands do we see in overflow?

Back 29

only see one band between beta region and IgG region. If you only see this band, think about bence jones, myoglobinuria (rhabdomyolysis) or hemoglobinuria (hemolysis).

Front 30

damage to tubules causes leakage of what enzyme?

Back 30

NAG (N-acetylglucosaminidase). Measure with dipstick

Front 31

what are three new markers for acute kidney injury?

Back 31

NGAL (neutrophil gelatinase associated lipocalin)

KIM-1 (kidney injury marker)

L-FABP (liver fatty acid binding protein)

NGAL goes up 3 days before BUN and creatinine do!

Front 32

what pigment makes urine yellow?

Back 32

urochrome pigment

Front 33

what condition has high porphobilinogen in urine?

Back 33

acute intermittent porphyria

Front 34

what if there is a very increased specific gravity in the urine?

Back 34

think about x-ray contrast

Front 35

how is glucose measured in urine? When is it falsely low?

Back 35

glucose measured by glucose oxidase. Falsely low in people taking vitamin C.

Front 36

how is bilirubin measured in urine?

Back 36

diazo reaction

Front 37

how is urobilinogen measured in urine?

Back 37

Erlich's reagent

Front 38

how are ketones measured in urine?

Back 38

nitroprusside

Front 39

on urine dipstick, how is blood detected? what can give false positive?

Back 39

hemoglobin is detected by peroxidase. Myoglobin or hemoglobin from hemolysis can give false positive. Look under microscope for RBCs to rule out false positive.

Front 40

Is leukocyte esterase found in lymphocytes or granulocytes?

Back 40

granulocytes