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What criteria may indicate the need for a microscopic exam?
- positive leukocyte esterase
- positive blood
- positive protein
- positive nitrite
- positive glucose
- abnormal color or clarity
Macroscopic Screening Correlations:
- Color: blood
- Clarity: hematuria vs. hemoglobinuria/myoglobinuria; confirm pathologic or nonpathologic cause of turbidity
- Blood: RBCs/RBC casts
- Protein: Casts/cells
- Nitrite: bacteria/WBCs
- Leukocyte esterase: WBCs/WBC casts/bacteria
- Glucose: yeast
Commerical systems have been developed in order to improve ___________ of the procedure.
- urine should be fresh or adequately preserved
- refrigeration may cause precipitation of amorphous urates & amorphous phosphates; warm specimen to 37C if necessary
- mix the specimen
- 10-15 mL is centrifuged in a conical tube for 5 minutes @ 400 RCF
Examination of the Sediment:
- minimum of 10 fields under both low (10x) and high (40x) power
- examine around the edges
- use high power to enumerate (semi-quantitative)
- supravital stain used to differentiate renal tubular epithelial cells from transitional epithelial cells and PMNs
- delineates structure and contrasting colors of the nucleus and cytoplasm
- identifies WBCs, epithelial cells, and casts
- Live PMNs: will not take up the stain
- Dead PMNs: may appear similar to RTE cells
- Squamous Epithelial cells: orange-purple nucleus; blue-purple cytoplasm
- Transitional epithelial cells: appear blue
- Renal Tubular Epithelial cells: take up both dyes resulting in an azurophilic appearance; dark purple nucleus; orange-purple cytoplasm
Sudan III & Oil Red O:
- stains triglycerides and neutral fats orange-red
- identifies free fat droplets and lipid-containing cells and casts
- differentiates gram positive and gram negative bacteria
- identifies bacterial casts
- methylene blue and eosin Y stains eosinophilic granules
- identifies urinary eosinophils
- enhances visualization of the elements with low refractive indices, such as hyaline casts and mixed cellular casts
- contains a condenser ring and a phase objective ring
- bright-field microscopy with two polarizing filters
- aids in the ID of cholesterol in oval fat bodies, fatty casts, and crystals
- provides a 3-D image showing very fine structure detail
- provides a layer by layer image of specimens
- smooth, non-nucleated biconcave disks
- identified using the 40x objective
- concentrated urine (hypersthenuric): RBCs may appear shrunken and crenated
- dilute urine (hyposthenuric): RBCs may absorb water, swell, and burst leaving only their cell membrane
RBCs that absorb water, swell, and burst leaving only their cell membrane are known as
__________ is a neutrophil that has absorbed water and has become swollen.
Brownian movement of the granules produce a sparkling appearance.
__________ are seen in drug-induced interstitial nephritis and renal transplant rejection.
The preferred stain is ____________.
- Hansel's stain
Squamous epithelial cells:
- largest cell found in the urine
- abundant, irregular cytoplasm with a prodominent nucleus (fried egg appearance)
- originates from the linings of the vagina and urethra (more common in females)
- NO clinical significance
__________ is a squamous epithelial cells with Gardnerella vaginalis, tiny gram-variable rods and coccobacilli.
Transitional epithelial cells:
- originate from the lining of the renal pelvis, ureters, bladder, and upper portion of the male urethra
Renal tubular epithelial cells (RTE):
- most clinical significant of all urinary epithelial cells
- small dense eccentrically placed nucleus
RTE cells originate from the ______________ & may have have coarsely granulated cytoplasm.
proximal convoluted tubules
Identification of oval fat bodies is confirmed by staining with __________ or ___________.
- Sudan III
- Oil Red O
Lipiduria is associated with severe damage to the glomerulus caused by ___________.
A characteristic ____________ is formed in the oval fat droplets that contain cholesterol.
- protein material produced by the glands of the lower genitourinary tract and the RTE cells
- NO clinical significance
Casts are formed within the lumens of the ________________ and _______________.
distal convoluted tubules and collecting ducts
What promotes the formation of casts in urine?
-high solute concentration
-slow movement of filtrate
-reduced filtrate formation
0-2 hyaline casts/lpf is *normal*
Colorless and easily overlooked
-Found in increased numbers following strenuous exercise, dehydration, heat exposure, emotional stress
-Hyaline casts will readily **dissolve in alkaline urine
-NO clinical significance
-Clinical Significance: Indicates bleeding the nephron
-The blood dipstick reaction will be positive and you should see free-standing RBCs in the urine specimen
*Pyelonephritis* (infection or inflammation within the nephron)
-Mostly composed of neutrophils
-Bacterial casts may also be seen
-Seen with oval fat bodies and free fat droplets in disorders causing lipiduria
-Associated with *Nephrotic Syndrome*
*Indicates extreme renal stasis*
*Signals the presence of CHRONIC RENAL FAILURE*
-Has notched along the sides
AKA: Renal Failure Casts
*Like waxy casts, these represent urine stasis*
-it is a mold of the distal tubules that has experienced destruction of the tubular walls
-Precipitation is subject to changes in temperature, solute concentration, and pH, which affects solubility
-*pH is a valuable aid in the id of the crystals*
Uric Acid Crystals
-Associated with high levels of purines and nucleic acids
-Often seen in leukemia and gout patients
Calcium Oxalate Crystals
-"Star", Envelope, or dumbbell shaped
-Massive amounts found in antifreeze poisoning
Crystals Present in Alkaline Urine
Ammonium Biurate Crystals
-Yellow brown "thorny apples"
-will convert to uric acid when acetic acid is added
Calcium carbonate Crystals
-Small, colorless dumbbell or spherical in shape
-NO clinical significance
Abnormal Crystals in Urine
Radiographic Dye Crystals
Three rarely seen crystals that may be present in patients with severe liver disorders:
Tyrosine (needled shaped)
Leucine (Wagon Wheel)
Bilirubin (Characteristic yellow color)
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