103114 GFR Flashcards
normal values for serum creatinine
men: 0.9-1.3 mg/dl
women: 0.8-1.0 mg/dl
children 0.1 to 1.0 mg/dl
GFR equation
UFR * urine concentration / serum concentration
describe the changes that happen with decreased GFR to half of original
initially, in first day, urine concentration of creatinine will be halved
however, soon, as serum concentration increases, urine concentration of creatinine will be normal (new steady state is established with higher serum concentration of creatinine)
when do you need dialysis?
when GFR is under 10 ml/min
where is there imprecision?
creatinine measurement
24 hr urine collection–for calculating clearance of creatinine or inulin (may forget to collect urine)
also the formula you use to calculate GFR (creatinine production is diff among diff age groups, race, gender)
what about using GFR formulas in acute kidney injury or acute renal failure?
cannot use the formulas because the formulas are for steady state
how do you quantify urine protein?
24 hour urine
spot urine sample (doesn’t correspond perfectly to 24 hr value)
pathophysiology of proteinuria
usually, several grams/day of plasma protein go through glomeruli. however, tubular reabsorption reabsorbs several grams/day
in glomerular disease, glomerular protein leak overwhelms tubular reabsorption. you get loss of albumin and low plasma oncotic pressure leading to edema
in health, what is the maximum of urine protein per day?
150 mg/day (not detected on UA)–of which most are TUBULAR proteins
larger amounts are graded semi-quantitatively as 1, 2, 3, or 4+
urine protein greater than 3 g/day may cause nephrotic syndrome, with edema
can proteinuria be due to non-kidney causes?
yes, you can have overproduction of proteins by cells so proteins are too high in serum and protein (like in diseases like myeloma)
