LAB - Urinalysis Module Flashcards
urine sample types
- random
- first morning
- 24 hour
- midstream
- catheterized
- suprapubic
when should urine specimens be processed?
within 2 hours of collection
- if not possible = store at 2 -8 C; protected from light
first-morning urine
- most concentrated
- ideal specimen for routine screening
- purpose: routine, pregnancy, orthostatic protein
24 hr/timed specimen
- some solutes measured in urine exhibit diurnal variation
- carefully timing these collections allows for accurate quantitative measurement of changes
- purpose = quantitative tests
catheterized urine sample
- tube passed through urethra and into the bladder to collect
- this urine is sterile
- purpose = bacterial cultures
midstream clean catch
- the genital area is cleaned before patient voids a small amount of urine to the toilet; then into container
- reduces sample contamination with epithelial cells and skin flora
- purpose = routine, bacterial cultures
suprapubic urine specimen
- needle inserted through abdomen into bladder to collect urine
- sterile
- purpose = bacterial culture, cytology
overview of urinalysis
physical
chemical
microscopic
physical examination of urine
- color
- clarity
- odor
- specific gravity
chemical examination of urine
- leukocyte esterase
- nitrites
- urobilinogen
- protein
- pH
- blood
- ketones
- bilirubin
- glucose
microscopic examination of urine
to evaluate microscopic elements present in urine sediment under specific circumstances
- casts
- cells
- crystals
- microorganisms
urine colour can be affected by:
- concentration (hydration)
- excreted metabolites
- medications
- chemicals
- cellular content
when is urine amber in colour?
- bilirubin (pathological)
- dehydration (non-path)
when is urine pink/red?
- RBCs (cloudy), hemoglobin (clear), myoglobin, porphyrins (pathological)
- beets, methyldopa (non-pathological)
when is urine orange?
- bilirubin (pathological)
- carrots, riboflavin, rhubarb (non-path)
when is urine brown/black?
- bilirubin, melanin, methemoglobin (path)
- iron compounds, levodopa, quinine (non-path)
when is urine red/brown?
porphobilin
when is urine blue/green?
- biliverdin, Pseudomonas (pathological)
- methylene blue (non-path)
cloudiness of urine can be caused by
precipitating amorphous substances
gradine urine clarity
- look from top and side of sample
- ensure it is adequately mixed before examination
dipstick urinalysis
- routine
- uses reagent strips
- strips composed of absorbent chemical pads attached to plastic strip
- colorimetric or enzymatic rxn occurs when pad comes into contact with urine
- after specific time = colour compared to a chart
= semiquantitative measure
a positive ___ ____, ____, _____ or _____ dipstick requires microscopic analysis
- leukocyte esterase
- nitrite
- protein
- blood
dipstick urinalysis - nitrite
- screening for UTIs (bacteriuria)
- cystitis, pyelonephritis
- Enterobacteriaceae produce reductase, reducing nitrate to nitrite
- Greiss reaction
> any shade of pink is pos
> bacteria must have sufficient contact tie with nitrate to produce nitrite (4 hrs)
Greiss reaction
- nitrite urinalysis (dipstick)
- acidic pH, nitrate reacts w aromatic amine to form a diazonium salt
- salt reacts with tetrahydro benzoquinoline to produce pink azo dye
false positives in nitrite test for dipstick
- improper storage
> leading to bacterial growth - pigmented urine and colour markers
false negatives for nitrite disptick urinalysis
- gram pos bacteria or yeast causing infection
- low contact time
- high ascorbic acid
- high specific gravity
- no nitrate in diet
- reduction of nitrite to nitrogen in high bacterial cocntn
- antibiotics
urobilinogen dipstick urinalysis
- small amount is normally found in urine
- degradation product of bilirubin
- increased in liver disease and hemolytic disorders
- Ehlrich reaction
- negative, 0.2, or 1
Ehlrich reaction
urobilinogen reacts with p-dimethylaminobenzaldehyde at an acidic pH
- produces a range of pink-red colours
urobilinogen dipstick urinalysis false positive
- Ehrlich-reactive compounds
> Porphobilinogen
> some drugs - pigmented urine and colour maskers
urobilinogen dipstick urinalysis false negative
- improper storage
> exposure
> storage at room temperature - acidic urine
leukocyte esterase dipstick urinalysis
- leukocytes are not normally found in urine
- increased urinary leukocytes are found in UTIs and inflammation
- detects esterases found in granulocytes
- leukocyte esterases hydrolyze an acid ester on the dipstick pad to produce an aromatic compound and an acid
- aromatic compound reacts with diazonium salt to produce an azo dye
false positives for leukocyte esterase dipstick
- strong oxidizing agents
- color markers (nitrofurantoin)
false negatives for dipstick urinalysis leukocyte esterase
- protein >5 g/L
- glucose >30 g/L
- ascorbic acid
- oxalic acid
- high specific gravity
- antibiotics (gentamicin, cephalexin, cephalothin, tetracycline)
protein dipstick urinalysis
- persistent proteinuria is associated with glomerular or tubular damage
- test strips primarily detect albumin
protein error of indicators (protein dipstick)
> indicators release protons when proteins are present
proteins accept protons from the indicator
at a buffered constant pH 3.0, indicator is yellow
as protein conctn increases, colour changes from yellow to green and blue
semiquantitative results
false positive for protein urine dipstick
- highly buffered alkaline urine
- prolonged contact of pad with urine (washes buffer off)
- high specific gravity
- pigmented urine
false negative for protein urine dipstick
non-albumin proteins
dipstick urinalysis = pH
- used to detect acid-base disorders
- under normal kidney function
> acidic pH = respiratory or metabolic acidosis
> alkaline pH = respiratory or metabolic alkalosis - double indicator system
> methyl red (colour change from pH 4 to 6; red to yellow)
> bromothymol blue (colour change at pH 6 to 9; yellow to blue)
false increase for pH dipstick
- improper storage
> urine turns alkaline on standing
> pH > 8.5 is not physiologically possible
false decrease for pH dipstick
- run-over from adjacent protein pad buffer
blood dipstick urinalysis
- hematuria (renal calculi, glomerulonephritis, pyelonephritis, trauma)
- hemoglobinuria (transfusion rxns, hemolytic anemia, severe burns, infections)
- myoglobinuria (rhabdomyolysis, trauma/crush syndromes, drug abuse, toxic to renal tubules)
blood dipstick reaction
- peroxidase-like activity of hemoglobin catalyzes a rxn between peroxide from Hb or myoglobin and a chromogen
- produces an oxidized blue-green chromogen
false positive for blood dipstick
- menstrual contamination
- strong oxidizing agents
- bacterial peroxidase
false negative for blood dipstick
- high SG crenates red cells
- high nitrite concentrations
- improper mixing = red cells settle at bottom
SG for dipstick urinalysis
- density of a solution when compared to an equal volume of distilled water (SG 1.000) at same temp
- urine has dissolved solutes, SG measures the density of dissolved solutes
> isosthenuric = 1.010
> hyposthenuric = <1.010
> hypersthenuric = >1.010 - monitors hydration and dehydration
- measures the kidney’s ability to concentrate urine
- decreased in diabetes insipidus
reaction of SG dipstick
- reagent strip contains a polyelectrolyte in alkaline medium and pH indicator
- polyelectrolyte releases protons to be released in proportion to amount of ions in urine
- higher the urine conctn, the greater the amount of protons released and the lower the pH
- indicator measures pH change from blue to green to yellow
false positive and negative of SG dipstick
FP
- high protein (anions)
FN
- urine pH >6.5; added 0.005 to SG readings to correct
ketones dipstick urinalysis
- intermediate products of liver fat metabolism
- along with acetone, acetoacetic acid (detected by test pad), B-hydroxybutyrate
- monitoring type I diabetes mellitus
> ketonuria indicates insulin deficiency - starvation, strenuous exercise, vomiting
- inherited metabolic disorders
- malabsorption/pancreatic disorders
reaction for ketones dipstick
- acetoacetic acid in alkaline conditions reacts with sodium nitroprusside
- produces purple colour
false pos for ketones dipstick
- highly pigmented urine and colour maskers
- large amounts of levodopa
- medication with sulfhydryl groups (MESNA, captopril)
false neg for ketones dipstick
- improper storage
> bacterial breakdown of acetoacetic acid
> volatilization of acetone
bilirubin dipstick analysis
- conjugated bilirubin is early indicator of liver disease
> hepatitis, cirrhosis, other liver disorders - biliary obstruction
> gallstones, tumors - diazo reaction
Diazo rxn
bilirubin dipstick
- bilirubin reacts w diazonium salt in acid medium
- produces a pink to violet azo dye
false pos in bilirubin dipstick
- pigmented urine and colour maskers
- medication
false neg in bilirubin dipstick
- improper storage
> exposure to light - high ascorbic acid
- high nitrite
glucose dipstick urinalysis
- detection and monitoring of DM
- not normally in urine
- glucose appears in urine when levels exceed renal threshold
> DM, advanced renal disease, pancreatitis, pregnancy, hyperthyroidism - glucose oxidase rxn
glucose oxidase rxn
- glucose dipstick
- double sequential enzyme rxn
> glucose oxidase catalyzes the oxidation of glucose into gluconic acid and peroxide
> peroxidase catalyzes the rxn between the peroxide and a chromogen
false pos in glucose dipstick
- contamination with oxidizing agents or detergents
false neg for glucose dipstick
- high ascorbic acid
- high ketones
- high SG and low temps decrease senstivity
- improper storage = bacterial glycolysis
supravital stain used for urine microscopy
Sternheimer-Malbin
> crystal violet and safranin
> staining the sediment facilitates the ID and differentiation o cells, crystals, casts, and other microscopic elements by increasing their contrast
what are casts?
- made up of uromodulin (Tamm-Horsfall protein) matrix
- formed in lumens of distal and convoluted tubules
- under normal conditions, uromodulin is excreted by renal tubules at a constant rate
factors affecting cast formation
- renal stasis
- increase acidity
- presence of abnormal ionic or protein constituents
characteristic of casts
parallel sides and rounded ends
broad vs narrow casts
- broad casts can be formed in collecting ducts
- narrow casts = ascending loop of Henle or distal convoluted tubule
hyaline cast
- colourless with visible protein gel matrix
- varied morphology
- increase visualization w phase contrast microscopy
- NOT clinically significant
- non-pathological (exercise, stress, dehydration, heat exposure)
- pathological (acute glomerulonephritis, pyelonephritis, chronic renal disease congestive heart failure with other cast types)
- correlating dipstick = + protein
hyaline casts sources of error
mucus, fibers, hair
granular casts
- can have fine or coarse granules in protein matrix
clinical significance of granular casts
- can originate from lysozymes of renal epithelial cells; disintegration of cellular casts, filtered protein aggregates
- nonpathological = increased in strenuous exercise
- pathological = increased in glomerulonephritis, pyelonephritis, renal disease
correlating urinalysis of granular casts
- dipstick = + protein
- other microscopy = RBCs, WBCs, cellular casts
RBC casts
- orange-red cells fill a protein matrix
- purplish if stained
- indicates bleeding in nephron and glomerular damage
- associated with glomerulonephritis and proteinuria
RBC casts correlating urinalysis
- protein or dipstick as well as + blood
- RBCs (other microscopy)
WBC casts
- neutrophils packed in a protein matrix
- may appear granular, have multi-lobed nuclei visible
0 infection or inflammation in nephron - present in pyelonephritis (upper UTI)
- also present in acute interstitial nephritis and glomerulonephritis
correlating dipstick for WBC cast
- protein
- leukocyte esterase
- WBCs (other microscopy)
correlating dipstick for WBC cast
- protein
- leukocyte esterase
- WBCs (other microscopy)
epithelial cell casts
- renal tubule epithelial cells
- indicates advanced renal tubular destruction resulting in urine stasis
- heavy metal, chemical, drug toxicology
- viral infections
- transplant rejection
- also seen in pyelonephritis w WBC casts
correlating dipstick and other microscopy for epithelial cell casts
- protein
- other microscopy = renal tubule epithelial cells
fatty casts
- seen with oval fat bodies and fat droplets
- highly refractile
- fat droplets and oval fat bodies attached to cast matrix
- can visualize with Sudan III or Oil Red O stains
- cholesterol ‘Maltese cross’
clinical significance of fatty casts
- disorders causing lipiduria
- most commonly seen in nephrotic syndrome
- also seen in toxic tubular necrosis, DM, crush injuries
fatty casts correlating urinalysis
- dipstick protein
- renal tubule epithelial cells
waxy casts
- brittle and refractile
- appear fragmented and have jagged ends
- side notches
- indicates extreme urine stasis and chronic renal failure
- seen with other cast types
- protein dipstick
- cellular and granular casts, WBCs, and RBCs
- sources of error = fibers, fecal material
erythrocytes in urine
- appear crenated in concentrated urine
- appear as ghost cells in dilute urine
- associated w glomerular membrane damage or vascular injury in genitourinary tract
- macroscopic hematuria
> cloudy red-brown urine
> over 100 cells/hpf
> advanced glomerular damage - microscopic hematuria
> early glomerular disorders; malignancy; renal calculi
correlating urinalysis for erythrocytes in urine
- blood for dipstick
- colour
sources of error for erythrocytes in urine
- yeast
- oil droplets
- air bubbles
leukocytes
- predominantly neutrophils
> larger than RBCs, contain granules, and are multilobed - hypotonic urine = swell and appear as glitter cells
- alkaline urine = lyse and lose nuclear detail
clinical significance of leukocytes in urine
- Pyuria = increased WBCs in infection or inflammation of the genitourinary system
> pyelonephritis, cystitis, prostatis, urethritis - glomerulonephritis, lupus erythematosus, interstitial nephritis, tumors
- eosinophils = drug-induced interstitial nephritis
- small amount in UTIs and renal transplant rejection
- stained with Hansel stain
correlating urinalysis for leukocytes in urine
- leukocyte esterase
- nitrite
- SG
- pH
sources of error for leukocytes
renal tubule epithelial cells
squamous epithelial cells
- abundant, irregular cytoplasm
- prominent nucleus
- not clinically significant
- from the linings of the vagina and female urethra
- may be increase in contaminated midstream clean catch collections
- correlating urinalysis = clarity
transitional epithelial cells
- smaller than squamous
- spherical, polyhedral, or caudate
- centrally located nucleus
- from renal pelvis, calyces, ureters, bladder, or upper male urethra
- increased after catheterization
- correlating urinalysis = clarity
sources of error for transitional epithelial cells
renal tubular cells = look similar to spherical transitional epithelial cells
renal tubular epithelial cells
- smaller than squamous epi cells
- coarse granular cytoplasm
> columnar or convoluted
> eccentric round nucleus - can originate from proximal convoluted tubule, distal or collecting duct
- presence = tubular necrosis
- leukocyte esterase and nitrite
oval fat bodies
- highly refractile RTE cells
- seen with free-floating fat droplets
- confirm by staining with Sudan III or Oil Red O under polarized light
> stain for presence of triglyceride and neutral fats
> cholesterol has a Maltese cross - RTE cells that have absorbed lipids
- nephrotic syndrome
- severe tubular necrosis, DM, bone trauma
urine crystals
- formed by precipitation of urine solutes
> inorganic salts, organic compounds, and medications - affected by: temp, concentration, pH, urine flow
- identification is based on pH and microscopic appearance
- classified as normal or abnormal
uric acid crystals
- normal acidic urine crystals
- colourless to yellow-brown
- various shapes; six-sided
- highly birefringent
- increased in gout
amorphous urates
- normal
- yellow-brown; appear pink macroscopically
- amorphous granules = may clump
- birefringent
acid urates
- rare
- larger granules with spicules
sodium urates
- rare
- needle shaped
calcium oxalate
- normal acidic/ neutral urine crystals
- can also be present in neutral and alkaline urine (rare)
- colorless
- various shapes = octahedral dihydrate (most common), dumbbell-shaped or oval monohydrate
> increased in ethylene glycol poisoning - birefringent
cystine crystals
- abnormal acidic urine crystals; rare
- colourless
- hexagonal plates (thick/thin)
- birefringent (thick)
- cystinuria = found in inherited metabolic disorders that prevent reabsorption of cystine
cholesterol in urine
- abnormal acidic urine crystals; rare
- coloirless
- rectangular plate and notched corners
- birefringent
- associated with lipiduria (nephrotic syndrome)
- seen with fatty casts and oval fat bodies
bilirubin
- abnormal acidic urine crystals; rare
- yellow/brown in colour
- clumped needles or granules
- liver disease
- seen with a positive bilirubin test strip
tyrosine
- abnormal acidic/neutral urine crystals (rare)
- colourless to yellow
- needles that form clumps or rosettes
- liver disease or inherited metabolic disorder
- seen with leucine crystals and a positive bilirubin dipstick result
bacteria in urine
- spheres or rods
- not normally in urine
- accompanied by WBCs in urinary tract infections
- may multiple due to improper storage at room temp
- nitrite and alkaline pH and + leukocyte esterase
- sources of error = amorphous phosphates
yeast
- refractile
- may contain buds
- may contain branched forms in severe infections
- seen n diabetic, immunocompromised patients with vaginal moniliasis
- accompanied by WBCs
- glucose and + leukocyte esterase
trichomonas vaginalis
- motile pear-shaped
- flagellated
- sexually transmitted parasite
- leukocyte esterase
spermatozoa
- tapered oval head with long thin tails
- found in both male and female specimens
- reporting in under-aged females may have legal implications
mucus in urine
- thread-like structures
- low refractive index
- may clump
- composed of uromodulin
- commonly seen in female specimens
leucine in urine
- abnormal acidic/neutral urine crystals
- rare
- yellow/brown
- spheres with concentric circles and radial striations
- associated with liver disease or inherited metabolic disorder
- seen w tyrosine crystals and a positive bilirubin dipstick result
rules for manual urinalysis count
- 10 fields at 10X for casts
- 10 fields at 40X for cells, crystals, and microorganisms
renal stasis
where slow urine flow leads to buildup of debris (stone) or potentiates infection
