Urinalysis Flashcards
What is the normal range for pH dipstick results
4.5-8.0
What are sources of error for the pH dipstick
increased alkalinity - bacterial growth (increased sitting), pH >8.5 is not possible and must be due to improper storage
increased acidity - improper reagent strip dipping technique (protein buffer can run onto pad and falsely decrease the pH)
What is the clinical significance of pH dipstick results
can correlate with acidosis or alkalosis if kidney function is normal
What is the normal result for the leukocyte dipstick
negative
What are sources of error for the leukocyte dipstick
false positive - coloured urine, contamination with an oxidizing agent
false negative - high concentration of proteins ( >5g/L), glucose (>30g/L), ascorbic acid, cephalexin, cephalothin, high specific gravity, lymphocytes that do not produce leukocyte esterase, not mixing before dipping the reagent stick
What is the normal result for the nitrite dipstick
negative
What are the sources for error for the nitrite dipstick
false positive - coloured urine, improper storage resulting in bacterial growth
false negative - urine not held in bladder for a sufficient time, high concentration ascorbic acid, high specific gravity
What is the clinical significance of leukocyte dipstick results
infection or inflammation
What is the clinical significance of nitrite dipstick results
gram negative bacteria infection
may aid in the diagnosis of asymptomatic cystitis, evaluation of antibiotic treatment and screening of urine for culture
What is the normal result for the protein dipstick
negative
What are the sources of error for the protein dipstick
false positive - coloured urines, highly buffered alkaline urines, high specific gravity, prolonged dipping of the dip stick
false negative - proteins other than albumin
What is the clinical significance of protein dipstick results
renal disease such as glomerulonephritis and nephrotic syndrome
What is the normal result for the glucose dipstick
negative
What are sources of error for the glucose dipstick
false positive - contamination with oxidizing agents or peroxide
false negative - low temperature, high specific gravity, high concentration of ketones or ascorbic acid, bacterial growth (glycolysis)
What is the clinical significance of the glucose dipstick
uncontrolled diabetes mellitus, renal disease, pregnancy
What is the normal result for the ketone dipstick
negative
What are sources of error for the ketone dipstick
false positive - coloured urine, bacterial growth, presence of MESNA or captopril
false negative - bacterial growth can break down acetoacetic acid
What is the clinical significance of the ketone dipstick
uncontrolled diabetes mellitus, insulin, inherited metabolic disorder, dieting, starvation, pregnancy, vomiting, diarrhea, strenuous exercise
What is the normal result for the blood dipstick
negative
What are sources of error for the blood dipstick
false positive - contamination of oxidizing agents, bacterial peroxidases, myoglobin, menstrual contamination
false negative - increased specific gravity, high concentrations of ascorbic acid, not mixing before dipping reagent strip
What is the clinical significance of the blood dipstick
hematuria - renal stones, glomerulonephritis, pyelonephritis, strenuous exercise
hemoglobinuria - IVH, transfusion reaction, severe burns, infection
myoglobinuria - observed in rhabdomyolysis, trauma and crush injuries, is toxic to nephron tubules and may cause acute renal failure
What is the normal result for the urobilinogen dipstick
negative (<16 umol/L)
What are sources of error for the urobilinogen dipstick
false positive - coloured urines, porphobilinogen
false negative - acidic urine, exposure to light, storage at room temperature
What is the clinical significance of the urobilinogen dipstick
hemolytic disorders, liver disease excluding hepatobiliary obstruction
What is the normal result for the bilirubin dipstick
negative
What are the sources of error for the bilirubin dipstick
false positive - coloured urines
false negative - exposure to light and storage at 4C, high concentrations of ascorbic acid or nitrites
What is the clinical significance of the bilirubin dipstick
hepatobiliary obstruction, gallstones, tumors in the bile duct, some liver disease such as hepatitis or cirrhosis
What is the normal result for specific gravity
1.005 - 1.030
What are the sources of error for the specific gravity dipstick
false increase - high concentration of proteins
false decrease - highly buffered alkaline urine (add 0.005 if pH is >/= 6.5 when read visually)
What is the clinical significance of the specific gravity dipstick
patient hydration status, ability of the kidney to concentrate urine, presence of ketones increases specific gravity
a value of 1.000 can be correlated with specimen adulteration
What is the normal colour/turbidity of urine
unremarkable/clear
What is the expected frequency of hyaline casts in urine
occasional
What is the expected frequency of granular casts in urine
occasional
What is the expected frequency of white cell casts in urine
negative
What is the expected frequency of red cell casts in urine
negative
What is the expected frequency of waxy casts in urine
negative
What is the expected frequency of fatty casts in urine
negative
What is the expected frequency of mixed cellular casts in urine
negative
What is the expected frequency of white cells in urine
occasional
What is the expected frequency of red cells in urine
occasional
What is the expected frequency of epithelial cells in urine
occasional
What is the expected frequency of renal epithelial cells in urine
negative
What is a clean catch or midstream urine
a method of collecting urine to reduce bacterial contamination from the skin. The genital area is cleaned and a urine specimen is collected part way through voiding the bladder
When is suprapubic aspiration most often used
to collect urine from infants for culture
When should urines be processed
within 2 hours of collection
What are the benefits and risks of refrigerating a urine sample
decreases bacterial growth but promotes crystal formation
What causes cloudyness in urine
amorphous urates (in acidic urine), amorphous phosphates (in alkaline urine), white or red cells in significant numbers
What causes an amber colour in urine
bilirubin or dehydration
What causes an orange colour in urine
bilirubin, carrots, riboflavin, rhubarb
What causes a pink/red colour in urine
red blood cells (if cloudy), hemoglobin (if clear), myoglobin, porphyrins, beets, methyldopa, senna
What causes a brown to red colour in urine
porphobilin
What causes a brown to black colour in urine
bilirubin, melanin, methemoglobin, iron compounds, levodopa, quinine
What causes a blue/green colour in urine
biliverdin, pseudomonas, methylene blue
What is the reaction for the pH dipstick
a double indicator principle using both bromothymol blue and methyl red
What are interferences of the pH dipstick
none known
What is the reaction for the leukocyte dipstick
esterases in the leukocytes hydrolyze an ester in the test pad to produce an aromatic compound which reacts with a diazonium salt to produce an azo dye
What is the reaction of the nitrite dipstick
Enterobacteriaceae reduce dietary nitrate in urine into nitrite, at an acidic pH nitrite reacts with an aromatic amine to form a diazonium compound which couples with an aromatic compound to produce a pink colour
colour development is not proportional to the number of bacteria present, any pink colour should be marked as positive
What is the reaction of the protein dipstick
the indicator dye releases protons in response to the proteins which are anionic and causes a colour change
What is pre-renal proteinuria
overflow proteinuria is caused by an increase in low molecular weight plasma proteins excreted in the urine, these proteins pass through the healthy glomeruli but due to increased concentrations it exceeds the reabsorption capability of the tubules
LMW proteins can be: acute phase reactants, hemoglobin, myoglobin or monoclonal free light chainsWh
What are two examples of renal proteinuria
glomerular leakage and tubular proteinuria
What is glomerular leakage
selective - the slits between the glomerular membrane podocytes are still intact but are wider than usual. Large molecules pass through the damaged glomeruli and are excreted, there is still some size selectivity
nonselective - proteins of any size can pass through the damaged glomerulus
What is tubular proteinuria
glomeruli are healthy but the renal tubules cannot reabsorb the low molecular weight What is the expected frequency of in urine proteins such as B2-microglobulin and immunoglobulin
rare, might be caused by heavy metal poisoning and nephrotoxic drugs
What is post-renal proteinuria
proteins found in the urine originate from the urinary tract as a result of inflammation, malignancy or injury. Uromodulin is produced by the renal tubular epithelial cells in the loop of henle and is always present
What is the reaction of the glucose dipstick
based on a double sequential enzyme reaction, glucose oxidase catalyzes the oxidation of glucose to form gluconic acid and hydrogen peroxide then peroxidase catalyzes the oxidation of a chromogen via the hydrogen peroxide
What is the reaction of the ketone dipstick
based on the development of colours ranging from beige to purple when acetoacetic acid reacts with nitroprusside
acetone does not react unless glycine is added to the reagent pad
What is the reaction of the blood dipstick
based on the peroxidase-like activity of hemoglobin which catalyzes the reaction of cellular peroxide and a chromogen, will detect both intact RBC and free hemoglobin
sensitivity of ~ 5 RBC/L
What is the reaction of the urobilinogen dipstick
based on the ehrlich reaction, in an acid medium p-diethylaminobenzaldehyde with a colour enhancer reacts with urobilinogen to produce a pink colour
What is the reaction of the bilirubin dipstick
bilirubin reacts with a diazonium salt in an acidic medium to form an azo dye
What is the reaction of the specific gravity dipstick
the test pad contains a polyelectrolyte and a pH indicator maintained at an alkaline pH, ionic solutes in the urine cause protons to be released from the pad which causes the surrounding pH to decrease and the bromothymol blue indicator changes from blue-green to yellow-green
What is a polarizing microscope used for
to detect birefringent urine elements such as uric acid and cholesterol
What is the morphology of a hyaline cast
there is a visible protein matrix, it appears translucent and is easier to see in subdued light or phase contrast
stain uniformly, pale pink or pale purple but sometimes do not stain at all
What is the clinical significance of a hyaline cast
they are not clinically significant and can be observed after exercise or stress
increased hyaline casts will be seen along with other cast types in pathological conditions
What is the morphology of granular casts
contain many fine or coarse granules that are usually evenly dispersed over the cast, can also include degenerated cell remnants
What is the clinical significance of granular casts
found in normal urine (following strenuous exercise) as well as in urine from individuals with renal disease
What is the morphology of RBC casts
intact erythrocytes can sparsely populate or completely fill the cast, unstained the cast will appear yellow or reddish brown, stained the RBCs appear purple or colourless within the pink matrix
What is the clinical significance of RBC casts
indicates bleeding in the nephron, most commonly observed in glomerulonephritis and are associated with proteinuria
What is the morphology of WBC casts
intact leukocytes can sparsely populate or completely fill the cast, usually composed of neutrophils and thus can look granular, staining can aid in identifying the multi-lobed nucleus,
should correlated with free leukocytes in the urine and urine dipstick
What is the clinical significance of WBC casts
indicates infection of inflammation in the nephron, commonly observed in pyelonephritis an can also be seen in acute interstitial nephritis and glomerulonephritis
What is the morphology of epithelial cell casts
they contain renal tubular epithelial cells
What is the clinical significance of epithelial cell casts
present in advanced renal tubular disease resulting in stasis, tubular disease may also be caused by heavy metals, drugs, viral infection, transplant rejection, can also be seen in pyelonephritis with leukocyte casts
What is the morphology of fatty casts
casts that contain unstained spherical, highly refractile fat droplets, neutral fats and triglycerides can be stained orange with Sudan II or Oil Red O, cholesterol can demonstrate as Maltese-cross under polarizing lights
should be accompanied by proteinuria and oval fat bodes, free fat droplets
What is the clinical significance of fatty casts
most commonly associated with nephrotic syndrome but may be observed in toxic tubular necrosis, diabetes mellitus, and crush injuries
What is the morphology of waxy casts
more refractile than hyaline casts, may have broken ends, colourless or uniform purple
What is the clinical significance of waxy casts
found in extreme urine stasis and are associated with chronic renal failure
What is the morphology of erythrocytes
appear as small, biconcave discs lacking nuclei but varies based on the urine specific gravity, can be crenated (hypersthenuria) or large and empty (hyposthenuria)
staining varies based on pH, pink purple (neutral pH), pink or unstained (acidic pH) or, purple (alkaline pH)
What is the clinical significance of erythrocytes
macroscopic hematuria (>100 cells/HPF) indicates glomerular disease or trauma and coagulation disorders
microscopic hematuria indicates early glomerular disease, malignancy or renal calculi
What is the morphology of leukocytes
larger than erythrocytes, round with multi-lobed nuclei, the neutrophils cytoplasm stains light purple and contain large purple staining granules
in hyposthenuria WBCs may swell and appear as glitter cells
neutrophil lysis is increased in alkaline urines and hyposthenuria
What is the clinical significance of leukocytes
Pyuria is found in infection (pyelonephritis, cystitis, urethritis) and inflammation (glomerulonephritis, lupus, interstitial nephritis) of the genitourinary system
other leukocytes cell types may be seen in urine
eosinophils are associated in drug-induced interstitial nephritis (differentiate from neutrophils with Hansel stain)
lymphocytes are found in increased numbers in renal transplant rejection
What is the morphology of squamous epithelial cells
large irregularly shaped cells with abundant light blue cytoplasm, small dense nuclei stain that stain dark orange-purple
What is the morphology of transitional epithelial cells
these cells are smaller than squamous cells and have various shapes, cytoplasm stains light purple and nuclei are well defined and stain blue-purple
What is the clinical significance of squamous epithelial cells
cells originate in the female genitalia and urethra and the lower urethra of men. They are not clinically significant
What is the clinical significance of transitional epithelial cells
cells originate in the renal calyx, bladder and ureters. Increased numbers are found following catheterization
What is the morphology of renal tubular epithelial cells
smaller than squamous cells and have various shapes, columnar with coarse granules cytoplasm stains light purple with an eccentric blue-purple nuclei
What is the clinical significance of renal tubular epithelial cells
cells originate from the proximal and distal convoluted tubules and collecting ducts of the nephron the presence of these cells indicates tubular damage
What is the morphology of oval fat bodies
renal tubular cells that have absorbed lipids, cells are highly refractile and the eccentric nucleus of the cell may be obscured
confirmation of the presence of fatty droplets composed of triglycerides or neutral fats can be performed by staining with Sudan III or oil red O
fatty drops composed of cholesterol appear as maltese crosses under polarized light
What is the clinical significance of oval fat bodies
lipiduria is associated with nephrotic syndrome as well as severe tubular necrosis and diabetes mellitus and trauma to long bones
usually seen with free fat droplets and fatty casts
What are calcium oxalate crystals
typically found in acidic urine but can be present at other pHs
colourless, birefringent and soluble in HCl
dihydrate form is octrahedral (envelope)
monohydrate is oval/dumbbell shaped
monohydrate form is significantly increased in ethylene glycol poisoning
What are uric acid crystals
found in acidic urine (<5.5)
colourless to yellow, birefringent and soluble in alkali
four sided flat plates, rhombic, wedges and rosettes
increased amounts associated with cytotoxic drugs and gout
What are amorphous urate crystals
found in acidic urine (<5.5)
pink or pink-orange in colour, yellow-brown granules, birefringent, soluble with alkali, can convert to uric acid with HCl
cold temperatures enhance precipitation
What are acid urate crystals
found in weakly acidic urines
larger granules with spicules
What are sodium urate crystals
needle shaped
What are amorphous phosphate crystals
white, granular in appearance similar to amorphous urates
cold temperatures enhance precipitation
differentiated from amorphous urates based on colour and pH
soluble with acid, insoluble at 60C
What are ammonium magnesium phosphate (triple phosphate) crystals
colourless, prism shaped (coffin lids), birefringent, soluble in acetic acid
may have feathered appearance as they dissolve
What are calcium phosphate crystals
rare
colourless, flat rectangular plates with one square end and one pointed end, birefringent and soluble in dilute acetic acid
What are calcium carbonate crystals
rare
small colourless spheres and dumbbells, resemble amorphous phosphates, soluble in acetic acid (produces carbon dioxide)
What are ammonium biurate
rare
yellow-brown spicule covered spheres often described as thorny apples, dissolve at 60C and convert to uric acid with addition of glacial acetic acid
usually seen in aged urines
What are cystine crystals
rare
colourless hexagonal plates, birefringent, soluble in NaOH
cystinuria is an inherited metabolic disorder
What are cholesterol crystals
rare
rectangular shaped flat plates with notched corners, highly birefringent
should be seen in conjunction with marked proteinuria as well as other signs of lipiduria
often confused with radiographic material
What are tyrosine crystals
rare
colourless to yellow, thin needles forming clumps or needles
in severe liver disease tyrosine is seen along with leucine and a positive bilirubin reagent strip test
can be observed in inherited metabolic disorders
What are leucine crystals
rare
brown to yellow spheres with concentric circles with striations radiating from the center of the crystal
in severe liver disease leucine is seen along with leucine and a positive bilirubin reagent strip test
can also be observed in inherited metabolic disorders
What are bilirubin crystals
yellow-brown fine needle clusters or granules
seen in hepatic disorders and should correlate with a positive bilirubin reagent strip test
What are bacteria
tiny spheres or rods
may indicate the presence of infection
may or may not correlate with positive nitrite and leucocyte tests
often confused with amorphous crystals
What is yeast
clear, small, ovoid refractile structures
may have buds and or mycelia
commonly associated with diabetic and immunocompromised patients alongside leukocytes
may also be seen with vagina moniliasis
What is trichomonas vaginalis
pear shaped cells with a waxy membrane and a long thin flagellum
a sexually transmitted parasitic infection
What is spermatozoa
oval head with long tapered tails
found in specimens from males or females but may have legal implications in female specimens
What is mucus
produced by the lower genitourinary system and primarily composed of uromodulin
clear, threadlike structure that is weakly refractile
What are the expected test results for a UTI
Dipstick - positive leukocytes, nitrites, blood
Microscopic - increased WBC, Bacteria, RBC, transitional epithelial cells
What is pyelonephritis
an inflammation of the kidney and renal pelvis due to infection, can be acute or chronic
What are the expected test results for pyelonephritis
Dipstick - positive leukocytes, nitrites, blood
Microscopic - increased WBC, Bacteria, RBC, transitional epithelial cells, WBC clumps, WBC, granular and waxy casts
What is glomerulonephritis
a thickening of the basement membrane, cellular proliferation. leukocyte infiltration and deterioration and scarring of the kidney
causes can be immunological, hereditary or metabolic
What are the expected test results for glomerulonephritis
Dipstick - positive protein and blood, low specific gravity
Microscopic - increased WBC, RBC, increased renal tubular epithelial cells, RBC casts, occasional WBC and renal cell casts
What is nephrotic syndrome
a disease of the renal parenchymal cells and is characterized by increased permeability of the glomeruli to proteins and lipids
What are the expected test results for nephrotic syndrome
Dipstick - positive protein, blood
Microscopic - lipiduria, oval fat bodies, increased RBC, casts (especially fatty), renal epithelial cells
