Urine Flashcards
What is the normal urine volume?
1 to 2 Liters
intake of water - insensible losses = urine output
What are signs of impaired dilution?
impaired dilution = impaired water excretion = water retention = hyponatremia
can be associated with low urine
high urine OSM (ADH present)
What is a normal specific gravity?
1.005 to 1.035
What are the categorical values for proteinuria?
1+ = 30 mg/dL
2+ = 100 mg/dL
3+ = 500 mg/dL
4+ = >2000 mg/dL
In the setting of metabolic acidemia, what should high urine pH raise suspicion for?
renal tubular acidosis
What is the maximal tubular reabsorption of glucose?
300 mg/dL
What is the urine anion gap in gap acidosis?
Urine K + Urine Na + Urine NH4 = Urine Cl + excreted anions (ex. ketoacids)
What pathological process would give a dipstick positive urine with no RBCs on microscopy?
rhabdomyolysis, hemolysis, and dilute urine
low specific gravity
What are the causes for hematuria?
GU cause
contamination
if RBC casts, proteinuria, or dysmorphic RBCs are present, suggests glomerulonephritis
causes of leukocyturia
contamination
infection (vaginitis, urethritis, bladder, kidney)
inflammation of the kidney or bladder - interstitial cystitis, interstitial nephritis, eosinophils classically associated, though evidence does not support
What do nitrites in the urine indicate?
some bacteria convert nitrates to nitrites
can be detected on dipstick
may be colonization or infection
hyaline cast
found in normal urine
can also found in people who are dehydrated
fomred due to slow flow of urine
What happens to the tubular cells in the case of AKI, morphologically?
proximal tubular cells lose their brush borders, undergo swelling, and blebbing of microvilli during injury, leading to cast formation
pigmented cast
suggests ATN or rhabdomyolysis
white cell cast
allergic interstitial nephritis
pyelonephritis
fatty cast
often can see maltese crosses
suggests nephrotic syndrome
maltese crosses
dead renal tubular epithelial cell filled with cholesterold from the lipiduria that occurs with nephrotic syndrome
urine indices for obstruction
300-500 U Osm
>40 UNa
>1 FE Na
don’t rely on indices to diagnose, better to image or use a foley catheter
What is the difference between prerenal and ATN?
depends on whether or not the tubules are working
in ATN, tubules are not functional, so spilling sodium (FE Na > 1 and UNa > 40)
can’t concentrate or dilute in ATN (UOsm < 350)
What are the urine indices for prerenal injury?
U Osm > 500
U Na < 20
FE Na < 1
What are the indices for AGN, and what features help diagnose it?
U Osm 300-500+
U Na < 40
Fe Na < 1
also presence of hematuria, proteinuria, and casts
What are the values for high and low potassium?
< 20 mEq/day is low - serum potassium is likely low
> 40 mEq/day is high - serum potassium is likely high
normal urine creatinine
15-20 mg/kg per day in females
20-25 mg/kg/day in males
normal urine sodium
100-260 mEq/24 hours (varies on intake)
normal urine potassium
25-125 mmol/24 hours (variable)
normal urine chloride
100-250 mmol/24 (variable)
When is a urine chloride measurement useful?
non-gap metabolic acidosis
metabolic alkalosis
What are the cuases of saline resistance metabolic alkalosis (U Cl > 20)?
alkali ingestion
adrenal excess - hyperaldosteronism, Cushing’s Disease, meds (steroids)
Bartter’s syndrome
Gitelman’s syndrome
Liddle’s syndrome
Licorice
“Refeeding” alkalosis
What are the causes of saline responsive metablic alkalosis (U Cl <10)
GI loss - vomiting, diarrhea (with Cl-), and adenoma
post hypercapnia
diuretics
What does specific gravity measure and what SG is isosthenuria?
measures how concentrated the urine is
isosthenuria occurs at 1.012
lower means dilure, and higher means concentrated
each unit of specific gravity approximates 1150 (range of urine Osm)/28 (range of urine Osm)
What is the calculation of urine osmols from specific gravity?
40 Osm per 0.001 unit of specific gravity
