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.
standardization
Specimen Preparation/Volume:
- 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)
Sternheimer-Malbin Stain:
- 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
Sternheimer-Malbin Staining:
- 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
Gram Stain:
- differentiates gram positive and gram negative bacteria
- identifies bacterial casts
Hansel Stain:
- methylene blue and eosin Y stains eosinophilic granules
- identifies urinary eosinophils
Phase-contrast microscopy:
- 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
Polarizing microscopy:
- bright-field microscopy with two polarizing filters
- aids in the ID of cholesterol in oval fat bodies, fatty casts, and crystals
Interference-contrast microscopy:
- provides a 3-D image showing very fine structure detail
- provides a layer by layer image of specimens
RBCs
- 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
(hyposthenuric urine):
ghost cells
__________ is a neutrophil that has absorbed water and has become swollen.
Brownian movement of the granules produce a sparkling appearance.
Glitter cell
__________ are seen in drug-induced interstitial nephritis and renal transplant rejection.
The preferred stain is ____________.
- Eosinophils
- 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.
Clue cell
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 ___________.
nephrotic syndrome
A characteristic ____________ is formed in the oval fat droplets that contain cholesterol.
Maltese cross
Mucus:
- 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?
-acid filtrate
-high solute concentration
-slow movement of filtrate
-reduced filtrate formation
Hyaline Casts
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
RBC Casts
-Clinical Significance: Indicates bleeding the nephron
*Acute Glomerulonephritis*
-The blood dipstick reaction will be positive and you should see free-standing RBCs in the urine specimen
WBC Casts
*Pyelonephritis* (infection or inflammation within the nephron)
-Mostly composed of neutrophils
-Bacterial casts may also be seen
Fatty Casts
-Seen with oval fat bodies and free fat droplets in disorders causing lipiduria
-Associated with *Nephrotic Syndrome*
Waxy Casts
*Indicates extreme renal stasis*
*Signals the presence of CHRONIC RENAL FAILURE*
-Has notched along the sides
Broad Casts
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
Crystal Formation
-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
-Acidic Urine
-Associated with high levels of purines and nucleic acids
-Often seen in leukemia and gout patients
Calcium Oxalate Crystals
-Acidic Urine
-"Star", Envelope, or dumbbell shaped
-Massive amounts found in antifreeze poisoning
Crystals Present in Alkaline Urine
Amorphous Phosphates
Triple Phosphate
Ammonium Biurate
Calcium Carbonate
Ammonium Biurate Crystals
-Yellow brown "thorny apples"
-will convert to uric acid when acetic acid is added
-Alkaline pH
-Old specimen
Calcium carbonate Crystals
-Small, colorless dumbbell or spherical in shape
-NO clinical significance
Abnormal Crystals in Urine
Cystine Crystals
Cholesterol Crystals
Radiographic Dye Crystals
Tyrosine Crystals
Bilirubin Crystals
Leucine 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)
