renal assesment Flashcards
function of nephron
regulation of water, electrolyte and acid base balance
excretion of products of protein and nucleic acid metabolism
what three ways do we evaluate renal function?
- eGFR
- BUN:Creatinine ratio
- urinalysis
what do you need to analyze eGFR?
you need to analyze eGFR? age gender race serum [creatinine]
what is a normal value for eGFR?
greater than or equal to 60 ml/min/1.73m^2
what are the sources of urine nitrogen?
deamination of proteins
enteric bacteria waste product
protein catabolized in a GI bleed
when BUN and creatinine increase what happens to kidney function?
decrease
what is a normal BUN:Creatinine ratio
10:1 to 20:1
what constitutes the best urine specimen?
first voided urine
mid-stream clean catch
usually b/c its concentrated so demonstrates ability of kidneys to concentrate and also concentrates infections
what can red urine indicate?
blood (menstrual)
beets
meds (pyridium - analgesic for relief of UTI pain)
what can orange urine indicate?
bilirubin
rifampicin (antibiotic)
what does black urine indicate?
alkaptonuria
what does yellow-brown/green-brown urine indicate?
bilirubin
what is alkaptonuria?
enzyme deficiency of homogentistic oxidase (required for the degradation of tyrosine)
what is another name for homogentisic acid?
alkapton
when does the urine darken in alkaptonuria?
upon standing
what can cause cloudy urine?
crystals
bacteria
rbc
pyuria (pus)
what does the urine specific gravity tell us?
renal concentrating ability
what is the RR for urine specific gravity?
1.003-1.035
what are the pathogenic causes of LOW urine specific gravity?
psychogenic polydipsia ADH deficiency (central DI) ADH resistance (nephrogenic DI)
what are the pathogenic causes of high urine specific gravity?
decreased renal perfusion
excess ADH
osmotic substances present in urine
is the urine specific gravity reliable as an index of a patient’s fluid status?
no
what is the chemical principle behind urine specific gravity testing?
H+ interacts with bromthymol blue indicator to form a colored complex
what is the PCT’s role in urine pH maintenance? what is the role of the DCT?
PCT - reabsorb HCO3-
DCT - secrete H+ and generate HCO3-
what are common causes of acidic urine?
DKA (ketones are acidic and FA buildup)
drugs that affect the transport of electrolytes (spironolactone - CHF, trimethoprim - antibiotic, heparin)
what are common causes of alkaline urine?
bacteria (usually increase pH as they break down urea in the urine to ammonia)
stones (calcium carbonate, calciumphosphate, magnesium phosphate)
what is alkaline urine?
> 8 pH
what is acidic urine?
<4.5
what causes glucosuria?
DM
gestational diabetes
what can cause bilirubin to appear in urine?
liver damage
obstructed bile ducts
(both allow conjugated bilirubin to enter the circulation and ultimately appear in urine)
if jaundice is due to red cell destruction
when does urobilinogen increase?
in the presence of hemolytic processes such as hemolytic anemia
what is urobilinogen?
a byproduct of hemoglobin breakdown
produced in intestinal tract as a result of the action of bacteria on bilirubin
when do ketones appear in the urine?
DKA
Starvation
increased lipolysis causing over production of FFA
when does protein appear in the urine?
glomerular damage resulting in “leaky” glomeruli
Presence in urine of cells or blood
check if urine is also positive for blood, WBC, UTI (culture)
when does blood appear in the urine?
malignancy
UTI
menstruation
presence in urine of large numbers of RBCs establishes diagnosis of hematuria
what two things can cause hematuria?
hemoglobinuria (lysis of RBC from things such as intravascular hemolysis)
myoglobinuria (muscle trauma or disease)
when does nitrite appear in the urine?
infection with gram negative bacteria
*depends on conversion of nitrate to nitrite by the action of bacteria that contain the necessary reductase
**positive result indicates a UTI
what is the significance of leukocyte esterase in the urine?
acute inflammation and presence of UTI
per high power field (HPF) it is normal to see how many erythrocytes? what is pathological?
normal is 1-2
path is > 3
what is a pathological value of bacteria per HPF?
more than 10
what is a pathological value of yeasts per HPF?
more than 10 - most likely a contaminant, but should correlate with clinical picture
what are casts?
when mucoproteins screted by tubule cells encase RBCs or endothelial cells
(tamm-horsfall mucoproteins)
crystals seen on microscopic examination can come from what types of deposits?
urate (ammonium biurate, uric acid) triple phosphate calcium oxalate amino acids (cysteine, leucine, tyrosine) sulfonamides
