Urinalysis Lecture 6: Microscopic Examination of Urine LMU

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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.

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

2% acetic acid:

- enhances nuclear detail
- differentiates WBCs and RTEs

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

Bright-field microscopy:

- routine urinalysis
- objects appear darker than the background

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

RBCs that appear shrunken and crenated (hypersthenuric urine):

What is the predominant WBC
found in the urine?

neutrophils

__________ 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

WBC Clump:

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

The presence of more than 2 RTEs per high power field indicates ______________.

tubular injury

Oval fat bodies:

- RTEs that have absorbed lipids in the glomerular filtrate

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

___________ is a pear shaped flagellate with an undulating membrane.

Trichomonas vaginalis

Yeast with pseudohyphae:

- positive glucose

Yeast budding:

- positive glucose

Spermatozoa:

- older male due to prostate conditions (prostate cancer)
- after sexual activity

Bacteria and WBC

- nitrite positive

Mucus:

- protein material produced by the glands of the lower genitourinary tract and the RTE cells
- NO clinical significance

_________________ protein is the major constituent of mucus.

Tamm-Horsfall

Casts are formed within the lumens of the ________________ and _______________.

distal convoluted tubules and collecting ducts

The major constituent of casts is _________________________.

Tamm-Horsfall protein

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

Epithelial Cell Casts (RTE Cell Casts)

*Advanced Tubular destruction*

Fatty Casts

-Seen with oval fat bodies and free fat droplets in disorders causing lipiduria
-Associated with *Nephrotic Syndrome*

Finely Granular Casts

Signal of cellular casts

Coursely Granular Casts

Signal of cellular casts

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*

Crystals present in ACIDIC urine

Uric Acid
Amorphous Urates
Calcium Oxalate

Uric Acid Crystals

-Acidic Urine
-Associated with high levels of purines and nucleic acids
-Often seen in leukemia and gout patients

Amporphous Urates

-Refrigerated urines
-Pink Sediment (uroerythrin)
-Acidic Urine (>5.5)

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

Amorphous Phosphate

-White Precipitate
-Doesn't dissolve on warming
-Alkaline pH

Triple Phosphate Crystals

-Alkaline urine
-"Coffin Lid"
-NO clinical significance

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

Cystine Crystals

-Kidney Stones (Renal Calculi)
-Proximal Tubules
-Cystinuria = sulfur smell

Cholesterol Crystals

-Nephrotic Syndrome
-Notched Plates

Radiographic dye Crystals

Very high specific gravity

Three rarely seen crystals that may be present in patients with severe liver disorders:

Tyrosine (needled shaped)
Leucine (Wagon Wheel)
Bilirubin (Characteristic yellow color)

Tyrosine Crystal

-Acidic Urine
-Needle Shaped
-Liver Disorders
-Positive Bilirubin dipstick result

Bilirubin Crystals

-Viral Hepatitis
-Yellow Haystack

Leucine Crystals

-Wagon Wheel
-Liver disorders
-Acidic urine

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