VII. Microscopic Examination of Urine

What are the Formed Elements involved in the Microscopic examination of Urine?

• Erythrocytes

• Leukocytes

• Epithelial cells

• Bacteria

• Yeast

• Fungal elements

• Parasites

• Mucus

• Sperm

• Crystals

• Artifacts

What are the Standard Rules for Microscopics?

1) Examine urine while fresh or properly preserved

2) 10-12 mL urine are centrifuged, leaving 0.5-1.0 mL for viewing

3) Report RBCs/WBCs using HPF; report casts and crystals using LPF

4) All formed elements must be identified and quantified

5) Methods include brightfield, phase contrast, and polarized

For normal urine, what is considered normally seen?

• RBCs → 0-2 HPF

• WBCs → 0-5 HPF

• Hyaline Casts → 0-2 LPF

• Several Epithelial Cells → HPF

• Certain Crystals

• Mucus

Erythrocytes:

1) What is the size?

2) What are the Normal Morphological characteristics?

3) What are the look-alike elements and how can it be differentiated?

1) Size = about 7 microns

2) Normal:

• Colorless disks

• In concentrated urine, they shrink and appear crenated

• In dilute or alkaline urine, they swell and lyse with release of Hb

  • Leaves empty cells known as Ghost cell

3) May be confused with yeast cells or oil droplets (highly refractile)

• Dilute acetic acid can be used to lyse RBCs, leaving only yeast, oil droplets, and WBCs

What is the Presence of RBCs associated with?

• Infections

• Toxins

• Cancer

• Circulatory problems

• Renal calculi

• Menstrual contamination

• Trauma

• Exercise

What is Pyuria?

• Increased WBCs in the urine that is usually indicative of infection in the urogenital tract

• Causes:

  • Bacterial infections

  • Pyelonephritis

  • Cystitis

  • Prostatitis

  • Urethritis

  • Nonbacterial resulting glomerulonephritis, lupus, tumors

Leukocytes:

1) What is the size?

2) What WBC is most predominantly seen?

3) What are Glitter cells?

4) What should be done if Eosinophils are suspected to be present?

1) Size = 10-15 microns

2) Neutrophils with multilobulated nuclei and cytoplasmic granules

3) When WBC swell in dilute alkaline urine (hypotonic), glitter cells are produced

• These have sparkling appearance due to Brownian movement of the granules

4) Special staining to visualize the cells

• Usually related to drug-induced nephritis or renal transplant rejection

Squamous Epithelial Cells:

1) What is the Size range?

2) Where are these cells normally found?

3) What is the morphological characteristics?

4) What is the Clinical Significance?

5) What are Clue Cells?

1) 30-50 microns

2) These epithelial cells line the lower urethra and vagina in women and the urethra of males

3) Largest of cells found in sediment with abundant irregular cytoplasm and central nucleus the size of RBC

4) These are not clinically significant; however, this can indicate improper collection via clean-catch method

5) In the presence of vaginal infection, clue cells may appear

• These are sq. ep. cells covered with Gardnerella vaginalis (coccobacillus)

Transitional Epithelial Cells:

1) Where are the cells normally found?

2) What is the normal morphology?

3) What is the clinical significance?

1) These cells line the renal pelvis, ureters, bladder, and upper urethra in males

2) These are smaller than squamous and vary in shape with central nucleus

• Can be spherical, polyhedral, caudate

3) No associated pathology except in large numbers with abnormal morphology (i.e., vacuoles or irregular nuclei)

• In this case, it may indicate renal carcinoma or viral infection

• Increased numbers may by present after invasive catheterization

Renal Tubular Epithelial Cells:

1) What is the morphological characteristics?

2) At what number is tubular injury is suggested?

3) What is the Clinical Significance

1) Small eccentric nucleus that vary in cell size and shape

• Can be rectangular, larger cells in PCT

  • Coarsely granulated cytoplasm

• Can be slightly larger than WBC-shaped cuboidal or columnar from CD

  • Finely granulated

2) When > 5/hpf are present

3) Can indicate:

• Renal cancer

• Renal tubular damage

• Pyelonephritis

• Toxic and allergic reactions

• Viral infections

What are the 2 types of RTE?

1) Bubble cells:

• Contain large, non-lipid-filled vacuoles

• Seen in Renal Tubular Necrosis

• Associated with dilation of endoplasmic reticulum before death of injured cells

2) Oval Fat Bodies:

• These have absorbed lipids are that are highly refractile and stain with Sudan III or oil red O

• Indicate Nephrotic Syndrome

What are Histiocytes?

• Misc. cells that indicate lipid-storage diseases

• These are filled with fat and are larger than oval fat bodies

What is Cylindruria?

• Casts in the urine

• These formed elements are unique to the kidney

How are casts formed?

• These are formed within the lumen of DCT and CT

  • Uromodulin is made the epithelial cells lining these portions

    • Uromodulin (Tamm-Horsfall glycoprotein) is poorly detected by reagent strip method

• Take on shape similar to the tubular lumen

• Formation is favored during Urinary Stasis

• Casts may have formed elements within or attached to their surface

• Casts also consist of some albumin and immunoglobulins

What are the Different Types of Casts?

1) Hyaline Cast

2) RBC Cast

3) WBC Cast

4) Bacterial Cast

5) Epithelial Cell Cast

6) Granular Cast

7) Waxy Cast

8) Fatty Cast

9) Broad Cast

Hyaline Cast:

1) What is the general morphology?

2) What is the normal count?

3) What is the Clinical Significance?

1) Colorless with varied morphology

2) Most commonly seen cast

• Norma = 0-5/lpf

3) Increased hyaline casts normally follow exercise, dehydration, heat, and emotional stress

• Associated with diseases:

  • Acute Glomerulonephritis

  • Pyelonephritis

  • Chronic renal disease

  • Congestive heart failure

RBC Cast:

1) What is the general morphology?

2) What is the Clinical Significance?

1) Orange to red color

• Contains hemoglobin and intact erythrocytes

2) Associated with:

• Strenuous contact sports

• Bleeding within the nephron

• Damage to glomerulus or renal capillaries as found in post-streptococcal infections

WBC Casts:

1) What is the general morphology?

2) What is the Clinical Significance?

1) Primarily contain neutrophils, thus appearing granular with multilobed nuclei

2) Associated with:

• Infections (pyelonephritis)

• Inflammation within the nephron (acute interstitial nephritis)

Bacterial Casts:

1) What is the general morphology?

2) What is the Clinical Significance?

1) Bacilli contained within the cast and bound to the surface

• Mixed cast containing bacteria and WBCs may occur

2) Pyelonephritis

Epithelial Cell Cast:

1) What is the general morphology?

2) What is the Clinical Significance?

1) Contain RTEs

2) Associated with:

• Advanced renal tubular damage

• Seen in heavy metal, chemical, drug toxicity

• Viral infections

• Allograft rejections

Granular Cast:

1) What is the general morphology?

2) What is the Clinical Significance?

1) These can be coarsely or finely granular

• Coarse = larger granules that may appear black

• Finely = appear gray or pale yellow

2) The granular appearance may result from glomerular precipitants, such as cellular casts or protein aggregates

• May be seen with hyaline casts following stress or exercise

Waxy Cast:

1) What is the general morphology?

2) What is the Clinical Significance

1) These casts contain surface protein as granules adhere to the cast matrix

• Formed from degeneration of granular casts

• High refractive index

• Colorless to yellow with a smooth appearance

• May have cracks or fissures on the sides

2) Associated with Chronic renal failure with significant urine stasis

Fatty Cast:

1) What is the general morphology?

2) What is the Clinical Significance?

3) How is this properly identified?

1) These are highly refractile and contain yellow-brown fat droplets

2) Seen with oval fat bodies in disease states that result in lipiduria

• Associated with:

  • Nephrotic syndrome

  • Toxic tubular necrosis

  • diabetes mellitus

3) Positive ID is by Sudan III stain or polarized light, which shows characteristics Maltese cross formation

Broad Cast:

1) What causes this to form?

2) What is the general morphology?

3) What is the Clinical Significance?

1) Formed in DCT or CD due to anuria

2) All types of casts can occur in broad form with the most common being granular or waxy

3) Highly suggests Renal Failure

Bacteria:

1) What is the Clinical Significance?

2) How are bacteria distinguished from amorphous crystals?

1) Associated with Lower and Upper UTI

2) Bacteria are motile, so they will present with tumbling or directional flagellar movement

What diseases is Yeast associated with?

• Yeast infection

• Vaginal Infection

• UTI

• Diabetes Mellitus

• Immunocompromised

What Parasites are most commonly found in the Urine?

• Trichomonas vaginalis

• Pinworm ova from Enterobius vermicularis due to fecal contamination

What is the Clinical Significance of sperm in the urine?

• Usually seen following intercourse or nocturnal emissions

• More important in forensic cases

• Male infertility

• Retrograde ejaculation

Mucus:

1) How is this formed?

2) What is the Clinical Significance?

1) Protein substance produced by RTE cells and urogenital strands

2) Not considered clinically significant

How are Crystals in urine formed?

• Formed by precipitation of urine salts, organic compounds, and medications

  • When an increased amount of solute is present, the ultrafiltrate becomes saturated and crystallize

  • Formation enhanced when urine flow thru the tubules is inhibited

• Will appear more frequently if urine stands at room temperature for prolonged time periods or from refrigeration

• Crystal formation can be altered by pH, temperature, and urine concentration

• pH will determine what types of crystals form

  • All clinically significant crystals are in acidic and neutral urine

Amorphous Urates:

1) How are these crystals formed?

2) What is the general morphology?

3) What is the Clinical Significance?

4) What happens to these crystals at alkaline pH?

1) Formed from urate salts of Na+, K+, Mg+, Ca2+

• Refrigerate samples will produce more amorphous urates and may appear as pink sediment due to the presence of uroerythrin on surface of the granules

2) Small, yellow to brown granules seen in large mounts (may make other urine elements difficult to see)

3) No clinical signficance

4) these crystals will dissolved

also by heaving above 60°C

What are the different types of Acidic Urine Crystals?

1) Amorphous Urates

2) Uric Acid

3) Calcium Oxalate

4) Bilirubin

5) Tyrosine

6) Leucine

7) Cystine

8) Cholesterol

Uric Acid Crystals:

1) What is the General morphology?

2) What is the Clinical Significance?

1) These appear yellow to orange/brown but can be colorless

• Pleomorphic shapes include four-sided flat plates, rhombic plates, wedges, and rosettes

2) Associated with:

• Gout

• Chemotherapy for leukemia

• Lesch-Nyhan syndrome

Calcium Oxalate Crystals:

1) Where is the urine oxalate derived from?

2) What is the general morphology?

3) What is the clinical significance?

1) derived from oxalic acid found in various food (e.g., tomatoes, asparagus, spinach, berries, oranges)

• oxalic acid is a metabolite of ascorbic acid

2) there are two forms:

• Colorless dihydrate form → octahedrak envelope or two pyramids joined at base

• Monohydrate form → dumbbell or oval shaped

3) Associated with renal calculi formation

• Monohydrate form is seen with ingestion of ethylene glycol (antifreeze)

Bilirubin Crystals:

1) When do these crystals form?

2) What is the general morphology?

3) What is the Clinical Significance?

1) These are formed when urine bilirubin exceed its solubility

2) These appear as fine needles or granules that are yellow to brown in color

3) Often seen in liver disease

• May see bilirubin crystals within cast as a result of viral hepatitis, causing renal tubular damage

Tyrosine Crystals:

1) What is the general morphology?

2) What is the Clinical Significance?

1) Fine delicate needles that can be colorless to yellow found in clumps or rosettes

2) Associated with:

• Severe liver disease

• Inherited diseases that affect amino acid metabolism

• May be seen with leucine crystals in urine that test positive for bilirubin

Leucine Crystals:

1) What is the general morphology?

2) What is the Clinical Significance?

1) Yellow to brown

• Oily-looking spheres with concentric circles and radial striations

• May be found with tyrosine crystals

2) Associated with:

• Severe liver disease

• Inherited diseases that affect amino acid metabolism

Cystine Crystals:

1) What is the general morphology?

2) What is the Clinical Significance?

1) Colorless, hexagonal plates

2) These crystals result from a congenital disorder that inhibits renal tubular reabsorption of cystine, causing cystinuria

• Associated with renal calculi formation

• Cystine is less soluble than lysine, arginine, and ornithine

Cholesterol Crystals:

1) What is the general morphology?

2) What is the Clinical Significance?

1) Clear, flat, rectangular plates with a notch in one or more corners

• More commonly seen following refrigeration

• Seen with fatty casts and oval fat bodies

2) Associated with nephrotic syndrome and other disorders that produce lipiduria

Which Crystals can form as a result of medications?

1) Ampicillin crystals → appear as colorless needles and may form bundles

2) Sulfonamide crystals → appear as colorless to yellow-brown in the form of needles, sheaves of wheat, fat formations, or rosettes

What is the Clinical Significance of Radiographic Dyes?

• Resemble cholesterol crystals

• Correlate with increased SG >1.050

What are the Crystals found in Alkaline Urine?

1) Amorphous phosphate

2) Triple Phosphate

3) Calcium Phosphate

4) Ammonium biurate

5) Calcium Carbonate

Amorphous Phosphate Crystals:

1) What is the general morphology?

2) What is the Clinical Significance?

3) How is this different/similar compared to the acidic amorphous urates?

1) Similar in appearance to amorphous urates and generally colorless

• Refrigerated samples appear as white sediment

2) Not clinically significant

3) These crystals are soluble in acetic acid and will not dissolved when heated above 60°C

Triple Phosphate Crystals:

1) What is another name for this?

2) What is the general morphology?

3) What is the Clinical Significance?

1) Ammonium Magnesium Phosphate

2) Colorless, three to six sided prism often resembling coffin lid

3) Not clinically significant; may be associated with UTI

Calcium Phosphate Crystals:

1) What is the general morphology?

2) What is the Clinical Significance?

1) Colorless, thin prisms or rectangular plates

2) Not clinically significant; may be associated with renal calculi formation

Ammonium Biurate Crystals:

1) What is the general morphology?

2) What is the Clinical Significance?

1) Yellow to brown spheres with striations on the surface

• Also can show irregular thorny projections (thorn apple)

2) Normal crystal commonly seen in old urine samples

• Converts to uric acid crystals if acetic acid added and dissolves at 60°C

Calcium Carbonate Crystals:

1) What is the general morphology?

2) What is the Clinical Significance?

1) small, colorless crystals with dumbbell or spherical shapes

2) Not clinically significant