chapter 4 Flashcards
how do you measure urine concentration
- osmolality
- specific gravity
urine composition
normal ranges of volume and solute
what effects urine concentration
diet, physical activity, and health
osmolality
concentration of particles (solutes) dissolved in urine (particles per unit of water)
–>determined in distal collecting tubules when ADH is present
–> normal urine osmolality is 1-3 times that of plasma
specific gravity
measures concentration of urine through density of urine compared to density of water
–> range: 1.002-1.035
polyuria
greater than 3 liters a day
causes of polyuria
water diuresis: ADH secretion is inadequate or receptors are ineffective
solute diuresis: involves glucose, urea, or sodium
oliguria
less than 400 mL a day
causes of oliguria
urinary obstruction, tubular dysfunction, and fluid loss
anuria
absence or cessation of urine excretion
cause of anuria
progressive renal disease or renal failure
what does renal concentrating ability tell us
assess tubular function by demonstrating tubules can produce concentrated urine specimen
–> measured through osmolality (solute number)
prevalent solutes in urine
- urea
- chloride
- sodium
fluid deprivation tests function
differentiates between causes of polyuria (diabetes insipidus)
how fluid deprivation tests work
water consumption is restricted and urine is checked 12 hours later
–> if concentrated test ends
neurogenic diabetes insipidus
ADH is decreased
nephrogenic diabetes insipidus
lack of renal response to ADH
renal clearance tests
asses glomerular filtration rate
–> how much plasma goes completely cleared through glomerulus over a certain time
glomerluar filtration rate
measures substances removed by glomerular filtration
–> insulin and creatinine (most common)
creatinine
waste that is constantly produced and excreted by kidneys
measuring creatine clearance
24 hr urine sample and drawing of blood (serum/plasma)
advantages of creatinine clearance
easily performed, accuracy and precision methods are well studied
disadvantages of creatinine clearance
if nonspecific jaffe method is used, creatinine values will be overestimated –> values close to insulin clearance results
estimated glomerular filtration
detects chronic kidney disease
–>used for high risk individuals with diabetes, hypertension, heart disease, or family history of kidney disease
accurate values of estimated glomerular filtration rate
most accurate values are less than or equal to 60 mL/min
beta-microglobulin
passes through glomeruli and 99.9% of it is reabsorbed by proximal tubules
–> marker of reduced tubular function
uses of beta-microglobulin
identifies early kidney transplant rejection
–>differentiates between tubular and glomerular diseases
screening for albuminuria
detection of albuminuria appears in diabetic nephropathy
–> early detection allows for additional testing and intervention to prevent diabetes
cause of albuminuria presence
increased glomerular permeability
–> changes in glomerular filtration
most important factor associated with glomerular proteinuria
hyperglycemia or diabetes mellitus
most common test used for GFR
creatinine clearance
most common test used for tubular concentrating ability
urine osmolaltiy
most common test for glomerular permeability to plasma proteins
urine protein electrophoresis
