Lab tests for the kidney (GFR and proteinuria)

Question 1

Normal kidney function

Answer 1

Homeostasis: excretion of waste products, water balance, acid-base balance, electrolyte balance

Hormonal: hemodynamics, RBC production, bone metabolism

Question 2

filtered rate vs excreted rate

GFR

Answer 2

filtered rate = Plasma concentration of x * GFR

Excreted rate= Urine concentration of x * Urine flow

rate= mg/min

GFR= (Urine conc. of X *Urine Flow)/ Plasma conc. of X

Clearance is the same

Question 3

characteristics of X measured via kidney

Answer 3

freely filtered, non-toxic, not secreted, not REAB, not changed during excretion

Exogenous markers: Inulin, iothalamate, Iohexol

Question 4

Creatinine and GFR

Answer 4

Creatinine is produced from metabolism of muscle creatine and from dietary meat intake

Released into circulation on a constant basis: freely filtered, non toxic, small amount in Proximal tubule is secreted, NOT REAB, not changed during excretion

Serum creatinein (in men .9-1.3, women .8 to 1, children .5 to 1)

Question 5

Creatinine production

Answer 5

since creatinine production is largely from muscle creatine, More muscle= more creatinine production

Blacks, men, and younger adults have more muscle mass,

Question 6

Calculated kidney function

Answer 6

creatinine clearance overestimates GFR due to a small amount of secretion in the tubules

Measured clearance needs 24 hrs of urine collection

creatinine production is dependent on muscle mass

Question 7

Cockcroft gault formula (not adjusted for body surface area)

Answer 7

Takes into account Serum Creatinine, Age, Weightt, Gender

CCr(Ml/min)= ( (140-age)*(weight Kg) ) / ( (Cr mg/dl) * 72) ) *.85 for female

Use with caution in obese or edamatous people (overestimates)

Question 8

Cystatin C

Answer 8

Protein produced by all nucleated Cells, freely filtered, production seems less affected by age and gender than creatinine,

Question 9

Chronic kidney disease

Answer 9

GFR < 60 ml/min/1.73 m2 for > 3 months

Other evidence of kidney damage ( you will need dialysis when the GFR is < 10 ml /min

Question 10

Acute kidney injury

Answer 10

Occurs over hours to days

Formulas are only valid for a steady state

Question 11

Definition of acute renal failure

Answer 11

acute and sustained reduction inn renal function

Biochemical definitions: .5 mg/dl or 25% increase in serum creatinine

Question 12

RIFLE criteria for stratifying AKI

Answer 12

Risk, Injury, Failure, Loss of function, End stage renal disease

Question 13

Creatinine for inidicator of kidney injury

Answer 13

lagging for creatinine to rise
Takes time for creatinine to rise

48hrs from time of injury

Question 14

proteinuria

Answer 14

Total urinary protein should be less than 150 mg/day

Urine protein of greater than 3.5 g/24 hrs is NEPHROTIC

Nephrotic syndrome has low serum albumin and edema

Question 15

Microalbuminuria (moderately increased albuminuria)

Answer 15

most of the total urinary protein is made up of tubular proteins
albumin in the urnie is abnormal