clinical skills II GU

examination of what constitutes urinalysis testing

physical, chemical, and microscopic contents

physical characteristics of urine

color, odor, clarity, specific gravity

chemical analyses of urine are

pH, detection of glucose, protein, blood, ketones, bilirubin, urobilinogen, nitrite, leukocyte esterase

microscopic examination of urine assesses for

cells, bacteria, crystals, casts, lipids, contaminants

a urinalysis should complement what in any pt undergoing renal evaluation

BUN and creatinine testing

normal urine color

pale yellow, straw to amber colored

color of normal urine is produced largely by

urobilin aka urochrome and pigments present in the diet

what is urobilin/urochrome

intestinal metabolite of bilirubin that undergoes enterohepatic recirculation w/ renal excretion

pts c elevated urine bilirubin or urobilinogen have what color urine

darkly colored, brown, green

causes of red urine

blood, beets, medications (pyridium, phenolphthalein), porphobilinogen

smokey/cloudy red/brown urine can result from what

intact red blood cells in the urine

what can cause orange urine

pyridinium, bilirubin, rifampin

what can produce black urine and when

alkaptonuria (homogentisic acid secretion in urine), makes urine black when exposed to air

green urine can result from

propofol, methylene blue (stain for lymphatics/search for fistula), indocyanine green, isosulfan blue

what can cause purple urine

UTI from pseudomonas, E coli, klebsiella, providencia stuartii, and enterococcus (when urine is alkaline)

cloudy urine can reflect the presence of

crystals, phosphates, urates, RBC, pyuria, bacteriuria, or lymph

when are amorphous phosphates present in urine

cooled normal urine at an alkaline pH

when are urates present in urine

normal cooled urine at an acidic pH

what is pyuria

WBC in urine

what is chyluria

milky white urine appearance from lymphatic leakage into the kidneys

what can cause chyluria

infection w/ Wuchereria bancrofti, noninfectious etiologies, genetic syndromes, fistulae

chyluria noninfectious etiologies

renal trauma, tumors, congenital lymphatic malformations (lymphangiomatosis)

chyluria genetic syndromes

Turner or Noonan

chyluria fistulae

lymphatic to vesical

what is urine specific gravity

ratio of the weight of urine to the weight of an equal volume of water (compares density)

what does urine specific gravity assess

capacity of renal tubules to concentrate/dilute urine

nl urine specific gravity

1.003 to 1.035

what can raise specific gravity and invalidate results

presence of glucose, protein, or blood (assess osmolality instead)

failure to concentrate urine can indicate

tubular dz, central DI, nephrogenic DI as a result of drugs (lithium), chronic hypokalemia, or chronic hypercalcemia

is urine specific gravity of 1.000 possible

nope! indicates water was submitted instead

what can help identify diluted urine/water in place of urine

temperature and creatinine concentration

what does very high specific gravity or unphysiological pH suggest

urine sample adulterated through addition of salt or bleach

freshly collected urine specimens should have a pH between

5.0-6.5 (irl 8.0)

what does urine pH over 8.0 suggest

delayed analysis or bacterial contamination

upon standing, an uncapped urine sample

loses CO2, raising pH

what do urease producing microorganisms do to pH

cleave urea, liberating ammonia that will form ammonium hydroxide, raising urine pH

decreased urine pH is the physiological and appropriate renal response to

systemic acidosis

renal tubular acidosis

failure to adequately excrete acids into urine in the setting of a systemic acidosis

increased urine pH occurs in the presence of

systemic alkalosis

urine dipstick for blood reacts with

heme

when is heme detected in urine

whenever RBC, hemoglobin, and/or myoglobin are present

dipstick positivity for blood does NOT identify

whether RBC, hemoglobin, or myoglobin are present singly or in combination

if RBC casts are present in urine, what is likely

nephritis or severe tubular injury

RBC in the absence of casts indicate

bleeding into the urinary tract or the presence of a hemorrhagic coagulopathy

what can cause bleeding in the urinary tract

inflammation, trauma, tumor, stone

when are casts more likely to be found

in a fresh, early morning urine specimen (casts are fragile)

what can happen to RBC if urine sample analysis is delayed

casts can fall apart and cells can lyse

when can free hemoglobin enter the urine

intravascular hemolysis

when is myoglobin released

w/ muscle dz or injury

hemoglobin and myoglobin are toxic to

the renal tubules

when can trace proteinuria be observed

pregnancy, fever, exercise, prolonged upright posture

functional proteinuria

nonpathologic proteinuria

what else can produce a positive protein dipstick

hemoglobin or myoglobin

how to detect bacteriuria

nitrite test on a urinalysis reagent strip, sensitive to the presence of clinically significant urinary bacteria concentrations (only for bacteria that convert nitrates to nitrites)

bacteriuria is often accompanied by

pyuria

is urine glucose useful for dx/monitoring DM

no

association between plasma and urinary glucose

only approximate, renal threshold varies, but typically glycosuria doesn’t develop until plasma glucose exceeds 150-180 mg/dL

trace glycosuria in pregnancy in the absence of DM

due to reduction in tubular threshold for reabsorption of glucose

glycosuria in the absence of hyperglycemia can indicate

renal tubular d/o including isolated defects in glucose reabsorption (renal glycosuria resulting from mutations in sodium-glucose linked transporter 2)

when/why is Benedict’s copper reduction rxn used

children under 2 to search for non-glucose inborn errors of metabolism like galactosemia or hereditary fructose intolerance (Benedict’s will be positive, glucose is negative)

bilirubin in urine indicates

extensive hemolysis, liver dysfxn, biliary obstruction

bilirubin in urine is what kind of bilirubin

conjugated, water soluble

urinary urobilinogen is derived from

bilirubin that is degraded by bacteria in the GI tract

is urobilinogen normal in urine

yes, undergoes enterohepatic recirculation to be excreted in urine

elevated urinary urobilinogen can be from

liver dz (failure to remove urobilinogen from blood), hemolytic anemia (bilirubin production increases urobilinogen generation)

what will cause urobilinogen to be absent from the urine

complete obstruction of the biliary tract

what else supports dx of complete obstruction of biliary tract

acholic stools (gray colored) due to absence of stercobilin (breakdown product of bilirubin)

when can ketones appear in urine

pts c poorly controlled DM, DKA, stressed hospitalized pts w/o DM, fasting/starving pts

where are urinary casts

distal convoluted tubules

what do urinary casts indicate

renal dz

cellular casts can be formed by

RBC, WBC, renal tubular epithelial cells

what kinds of casts can be found in kidney dz

granular casts (do not contain intact cells) and waxy casts, both are derived from degenerating tubular cells

when can renal tubular cells casts be observed

cases of acute tubular necrosis

abundant squamous cells in urine suggest

urine was not a clean catch sample

hyaline casts are composed of

protein, can be observed in the absence of dz

RBC casts indicate

glomuleronephritis

pyuria

increased numbers of WBC in the microscopic urine sediment, often considered to be at least 5 WBC/high powered field

where are leukocyte esterase enzymes found

in neutrophils

leukocyte esterase enzyme activity tests for

whether enzyme activity in neutrophil is intact or disrupted

where do WBC casts originate

tubules

WBC casts are consistent w/

pyelonephritis or noninfectious interstitial inflammation

when can kidney stones form

increased excretion of components found in stones or decreased urinary volume leading to elevated concentration

m/c found chemical constituents in renal stones

calcium, phosphate, oxalate

less common chemical constituents in renal stones

urate, cysteine

elevated concentration of calcium in urine can lead to

generation of calcium oxalate/calcium phosphate stones

increased concentration of oxalate in urine can occur in pts who have

excess absorption of dietary oxalate

Chron’s dz and oxalate

increased absorption from the ileum

ethylene glycol poisoning can produce

urinary oxalate crystals

renal tubular acidosis, pediatric growth failure, recurrent fractures, progressive renal failure, cardiac arrhythmias, death before 20 yo

oxalosis, an inborn error of metabolism that can produce oxalate stones

when can cystine accumulate in urine

defective transport of cystine out of urine by proximal tubules, allowing cystine to reach concentration at which it becomes insoluble

cystinuria and amino acids

defective reabsorption of dibasic amino acids arginine, ornithine, and lysine

high concentrations of urinary uric acid are found in pts c

gout, predisposed to form urate stones esp when urine pH is below 5.4

calcium carbonate and struvite stones occur in pts c

UTI, particularly proteus

crystals in microscopic urine exam

frequently observed, majority are nl urinary components

UTI categories

uncomplicated lower, uncomplicated upper/pyelonephritis, complicated

uncomplicated lower UTI involves

bladder and/or urethra

uncomplicated upper UTI/pyelonephritis involves

ureters, renal pelvis, kidney

complicated UTI involves

various sites w/i urinary tract

m/c UTI organism

E coli

what makes uropathogenic E coli different

genetically distinct from other intestinal strains, possess virulence factors that facilitate colonization of urinary tract epithelium