360 - Urinalysis Flashcards
types of urine collection techniques
routine void/random
midstream
catheter
suprapubic aspiration
pediatric
Why is the first-morning urine the recommended specimen for urinalysis
it’s the most concentrated
- can be a clean catch or midstream
catheter urine
- often contaminated with CNS
- insertion of thin rubber tube through urethra into bladder
suprapubic aspiration
usually infants for culture
needle inserted directly into bladder guided via ultrasound; urine drained
random urine specimens - acceptable for urinalysis?
acceptable for urinalysis but if urine has NOT been in bladder for four hours, urine nitrite may be undetectable
when should urinalysis be processed?
within 2 hours of collection as many physical characteristics unstable = bilirubin, urobilinogen, pH
which microscopic elements are unstable
cells and casts degrade upon storage while bacteria and yeast can multiply
how can we preserve urines
refrigeration
cold temps inhibit bacterial growth BUT promote crystal formation
APL does not accept urine specimens greater than 24h old
three general components of routine urinalysis
physical
chemical
microscopic
components of physical examination
- clarity: look down and sides of tube (clear, hazy [bottom not clear], cloudy, turbid)
- colour
T or F. Most urines are clear when voided and cloudiness occurs upon standing
T!
amorphous urates may precipitate in acidic urine
amorphous phosphates may precipitate in alkaline urine
LOTS of blood cells = cloudiness too
what is urine colour affected by?
concentration of sample
presence of excreted metabolites
medications
other chemicals
cellular content
normal urine colour
varies from pale yellow to dark amber
possible pathological cause of AMBER urine
bilirubin
possible no-pathological cause of AMBER urine
dehydration
which urine components are light sensitive
bilirubin
urobilinogen
porphyrins
possible pathological cause of ORANGE urine
bilirubin
possible non-pathological cause of ORANGE urine
carrots
riboflavin (vit B)
rhubarb
possible pathological cause of PINK to RED urine
red blood cells (CLOUDY)
hemoglobin (CLEAR)
myoglobin
porphyrins
possible non-pathological cause of PINK to RED urine
beets
methyldopa
Senna (laxative)
possible pathological cause of RED to BROWN urine
prophobilin
possible pathological cause of BROWN to BLACK urine
bilirubin
melanin
methemoglobin
myoglobin
possible non-pathological cause of BROWN to BLACK urine
iron compounds
levodopa (Parkinson’s)
quinine (Malaria)
possible pathological cause of BLUE to GREEN urine
Pseudomonas
biliverdin
possible non-pathological cause of BLUE to GREEN urine
methylene blue
how can colorimetric changes on urine regent pads be detected
manually or reflectance spec
prior to testing urine chemically, what must we do before using the strips
visually check them
- can change colour from moisture (especially NIT)
pH of normal urine
4.5 to 8.0, depending on amount of acid or vase excreted
physiologically impossible to go above or beyond (>8.0 = bacteria; <4.5 = adulteration)
what principle is the pH test based on
a double indicator system = bromothymol blue and methyl red
protons in urine react w anionic indicator dye to reduce the indicator dye and cause a colour change
false acidity of urine
excess urine on reagent pad can wash protein reagent pad buffer onto pH = falsely decreasing pH
if kidney function is normal, urine is acidic in …
resp and metabolic acidosis
T or F. All WBCs produce leukocyte esterase
F!
All but lymphocytes
how does the leukocyte reagent pad work?
granulocytic leukocytes hydrolyze an ester in test pad to produce aromatic compound and an acid
aromatic compound reacts with a diazonium salt to produce azo dye
false pos in leukocyte biochemical test
- colour maskers (beets, nitrofurantoin)
- contamination of collection container with an ox agent
false neg of leukocyte biochemical test
- protein >5g/L
- glucose >30 g/L
- ascorbic acid
- high SG
- cephalexin, cephalothin, gentamicin, tetracycline
- leukocytes settling to bottom (MIX PROPERLY)
clinical significance of leukocyturia
infections and inflammatory diseases such as UTIs and pyelonephritis
T or F. Nitrites are not found in normal urine
T!
Reaction in nitrites biochemical test pad
Greiss reaction - at an acidic pH, nitrite (after bacteria reduced nitrate) in the urine react w aromatic amine to form diazonium compound
- diazonium compound + aromatic compound = pink
NOTE: colour development is not proportional to number of bacteria present
urine nitrite indicates
- presence of bacterua
- may aid in diagnosis of asymptomatic cystitis
- evaluation of antibiotic treatment
- screening of urine for culture
T or F. Protein is not normally detected in urine
T!
healthy adults excrete less than 0.15g of protein per day and urine reagent strip usually do not detect this amount
The ability to detect bacteria using nitrite is dependent on: (3)
- bacteria’s ability to reduce nitrate to nitrite
- enough nitrate substance (diet)
- urine must be held in bladder for 4 hrs (first morning urine!)
first sign of glomerular damage
albumin in the urine
reaction for urine protein
- principle of protein error of indicators
- buffered pH of 3.00, colour of indicator is yellow
- indicator dyes release protons in response to proteins (ALBUMIN) which are anionic = indicator changes colour
false pos for proteins
- highly buffered alkaline urines
- high SG
- pigmented urines
- prolonged dipping of regent strip may remove buffer
false neg for proteins
negative result does not rule out presence of uromodulin, and globulin proteins (hemoglobin, myoglobin, monoclonal free lt chains)
clinical significance of proteins in the urine
persistent detectable proteinuria is associated w renal diseases such as glomerulonephritis and nephrotic syndrome
pre-renal proteinuria
- overflow proteinuria caused by increase in low MW plasma proteins
- these proteins pass through healthy glomeruli but increased concentration = exceeds the reabsorption capability of tubules
- low MW proteins may be APRs (Hb, Mb) or abnormal proteins such as monoclonal free light chains
renal proteinuria (glomerular leakage)
- selective: the slits between glomerular membrane podocytes are still intact but are wider than usual; large molecules such as albumin pass through and are excreted
- non-selective: proteins of any size can pass through the damaged glomerulus
tubular proteinuria
glomeruli are healthy but tubules cannot reabsorb low MW proteins such as B2-microglobulin and Ig; rare and may be caused by heavy metal poisoning and nephrotoxic drugs
post-renal proteinuria
proteins found in urine originate from urinary tract as a result of inflammation, malignancy, or injury
uromodulin is produced by renal tubular epithelial cells in loop of Henle and is always present in urine
T or F. Glucose is not found in normal urine
T!
T or F. Glucose is a semi-quantitative test
T!
one enzyme, glucose oxidase, catalyzes oxidation of glucose to form gluconic acid and H2O2
second enzyme = peroxidase, oxidizes chromogen by hydrogen peroxide
false pos for glucose
oxidizing agent and peroxide contamination can cause false positive
false negative for glucose
- sensitivity decreased by high SG or low temp
- high ketones may cause neg interference
- high concentrations of ascorbic acid
- bacterial glycolysis may decrease glucose results
clinical significance of glucose in the urine
- when blood glucose exceed renal threshold (11 mol/L)
- glycosuria most commonly associated w uncontrolled DM, advanced renal disease, and pregnancy
ketones in urine
produced in the liver during metabolism of fatty acids; urine strip only detects acetoacetic acid
nitroprusside
acetoacetic acid reacts with this to develop colour
acetone does not react unless glycine is added to pad
false pos for ketones
colour maskers
large amounts od levodopa metabolites or with compounds containing sulfhydryl groups (EX: MESNA and captopril)
false neg for ketones
under improper storage conditions, acetoacetic acid can be broken down by bacteria
clinical significance of ketones in urine
type I diabetics monitor insulin dosage
ketonuria combined with glycosuria indicates uncontrolled DM1
ketonuria is found in some inherited metabolic disorders (phenylketonuria)
times of physical stress = starvation, fasting, pregnancy, exercise, dehydration, vomiting
reaction of blood on urine pad
based on peroxidase-like activity of Hb, which catalyzes rxn of cellular peroxide and a chromogen
detects intact RBCs and free Hb
sensitivity of approximately five red blood cells/uL
false pos for blood
- presence of oxidizing contaminants in container (bleach)
- microbial peroxidase associated with UTI (E. coli)
- menstrual contam
- test strip equally sensitive to myoglobin as Hb
false neg for blood
- elevated SG
- erythrocytes will settle at bottom; MIX PROPERLY!
- high nitrite
most common cause of hematuria
renal calculi
glomerulonephritis
pyelonephritis
Transient hematuria can result from …
strenuous exercise
hemoglobinuria
- occurs when amount of free hemoglobin exceeds binding capacity of haptoglobin
- hemoglobinuria observed in intravascular hemolysis, trxns, severe burns and infections
myoglobinuria
rhabdomyolysis, trauma, crush injuries
toxic to nephron tubules and may cause acute renal failure
T or F. Urobilinogen is normally found in urine and give urine its characteristic colour
T! it is a water-sol degradation product of bilirubin
urobilinogen test rxn
Ehrlich rxn
- acid medium = p-dimethylaminobenzaldehyde + colour enhancer reacts with urobilinogen to produce pink colour
false positive for urobilinogen
colour maskers
porphobilinogen
false negative for urobilinogen
degraded by acidic urine, light, and storage at room temp
clinical significance of urobilinogen
increased amounts observed in hepatic disorders and hemolytic disorders
T or F. Bilirubin is a normal constituent of urine
F! it is not; conjugated, water-sol bilirubin can be found in urine
false pos for bilirubin
colour maskers
false neg for bilirubin
photo-labile and temp sensitive
high concentrations of ascorbic acid and nitrite may cause negative interference
clinical significance of bilirubin in the urine
- early indicator of liver disease = hepatitis cirrhosis
- also associated with bile duct obstruction: gallstones, tumors
- increased erythrocyte destruction does not produce bilirubinuria
the density of a solution compared to the density to an equal volume of deionized water at the same temperature
specific gravity
this affects SG
solute number and mass
the SG of normal urine
1.005 to 1.030
reaction of S on urine test pad
- test pad = polyelectrolyte and pH indicator maintained at alkaline pH
- ionic solutes in urine cause protos to be released from polyelectrolyte pad
- release of protons from pad cause surrounding pH to decrease and bromothymol blue changes to yellow-green
false pos for SG
high proteins
false neg for SG
highly buffered alkaline urines
add 0.005 to SG if pH is >/=6.5 when reading
clinical significance of SG
- can be used to monitor pt hydration & ability of kidney to concentrate urine
- SG of 1.000 = specimen adulteration
- SG will increase with high ketones
what is the refractive index of a solution dependent on
wavelength of light used
temp of solution
concentration of solutes in solution
refractometer and SG
measures SG indirectly by comparing the refative index of light in the air (1.000) to urine
how are refractometers calibrated?
using water and sodium chloride solutions
15C to 30C
refractometer reading can be corrected for presence of high glucose and protein
SG >1.035 measured by refractometer
= pt who receives radiocontrast media, dextran, mannitol
reagent test strip preffered!
microscopic analysis required if these are pos
leukocyte
nitrite
blood
protein
to standardize the microscopic examination of urine sediment, what must be maintained?
constant specimen, centrifugal force and sediment volume
stain used for urien sediment
Sternheimer-Malbin
supravital stain; safranin O and crystal violet
urinalysis procedure
- ten fields at 10X for casts
- ten fields at 40X for crystals, cells, microorganisms
SG equation
density of urine/ density of equal vol of water
isothenuria
1.010 SG
hypothenuria
urine with SG <1.010; dilute urine
hyperthenuria
urine with SG >1.010; concentrated urine
polarizing light microscopy
used to detect birefringent urine elements such as uric acid and cholesterol
- refract light in two directions; 90 degrees from each other
when are casts formed?
when uromodulin, a renal protein, congeals in distal tubules and collecting ducts during renal stasis
where are narrow casts produced?
distal tubles
broad casts
collecting ducts
how do cells get incorporated into casts?
if cells are present in tubular lumen when the congealing of protein occurs
clinical significance of hyaline casts
can be observed after exercise or stress
can be increased in pathological conditions
clinical significance of granular casts
can be found in normal urine (exercise) and in urine from individuals with renal disease
clinical significance of RBC cast
-bleeding in the nephron
- most commonly observed in glomerulonephritis and are associated w proteinuria
WBC cast typically composed of
neuts; so may appear granular
WBC cast significance
- infection or inflammation in the nephron
- commonly observed in pyelonephritis
- also seen in acute interstitial nephritis and glomerular nephritis
epithelial cell cast contains…
renal tubular cells
epithelial cell cast significance
advanced renal tubular disease => stasis
- may be caused by heavy metals, drugs, viral infections, transplant rejection
- also seen in pyelonephritis w leukocyte cast
casts that contain unstained, spherical, highly refractile fat droplets
fatty cast
neutral fats and triglycerides can be stained with
Sudan III( orange)
Oil Red O
fatty cast should be accompanied by
proteinuria and oval fat bodies, free fat droplets
cholesterol can demonstrate as …
Maltese cross under polarizing light
fatty cast most commonly associated with …
nephrotic syndrome and may be observed in toxic tubular necrosis, DM, crush injuries
waxy casts (3)
- more refractile than hyaline
- may have broken ends
- colourless or maybe a uniform purple
clinical significance of waxy casts
found in extreme urine stasis; chronic renal failure
T or F. Morphlogy of erythrocytes varies with urine specific gravity
T!
hypersthenuria = red cells appear
crenated
hyposthenuria = red cells appear
large and empty
staining of erythrocytes varies on urine pH
neutral = pink purple
acidic = pink/unstained
alkaline - purple
macroscopic hematuria
- clinical significance of RBCs in urine
- > 100 cells/HPF
- advanced glomerular isease
- truama and coag disorders
microscopic hematuria
- clinical significance of RBCs in urine
- early glomerular disease
- malignancy
- renal clculi
the predom type of leukocyte in urine
neutrophil
in __________, neuts may swell and appear as a glitter cells
hyposthenuria
neutrophil lysis is increased in …
alkaline urine and hyposthenuria
when are eosinophils seen in urine
- drug-induced interstitial nephritis
- can be differentiated using a Hansel stain
lymphocytes in urine
increased numbers in renal transplant rejection
these are REPORTED, and cells enumerated as part of WBC count
WBC Clumps
clinical significance of squamous epi cell
NOT significant
cells originate in female genitalia and urethra and lower urethra of men
these cells are smaller than squamous cells and have various shapes
transitional epi cells
- spherical, polyhedral, caudate
- cytoplasm light purple
- well-defined CENTRAL nuclei
clinical significance of transitional epi cells
- renal calyx
- bladder
- ureters
- catheterization
renal tubular epi cells
- not very common
- smaller than squamous cells and have various shapes
- columnar w coarse granules; oval, and cuboidal
- eccentric nuclei that stain blue-purple
clinical significance of renal tubular epis
- originate from PCT and DCT and CDs of nephron
- presence = tubular damage
renal tubular epi cells that have absorbed lipids
oval fat bodies
oval fat bodies confirmed with
polarizing microscopy
Sudan III or oil red O
cholesterol = maltese cross under polarized light
clinical significance of oval fat bodies
lipiduria is associated with nephrotic syndrome and severe tbular necrosis and DM and trauma to long bones
oval fat bodies, free fat droplets, and fatty casts usually seen together
- proteins also pos on dipstick
