UA: Crystals, Cells, and Casts

Flashcard Sets Combined

Casts in Urinary Sediment

• Casts in urinary sediment → differential diagnosis of renal disease

• Pure Hyaline casts may be seen in Proteinuria

• Small Hyaline cast seen transiently may occur with marked exercise or febrile conditions

• Casts with inclusions, such as RBC’s or WBC’s may be formed without a protein matrix

Types of Casts

Hyaline, Granular, WBC, RBC, Cellular and other casts (such as hyaline casts with inclusions), Waxy, Fatty, Epithelial

Hyaline Casts

• Hyaline casts = Renal Proteinuria: They form only with urinary protein.

• Tamm-Horsfall protein is key: This nephron-secreted protein is the main cast component.

• Acid/Concentration = Casts: Low pH and high solutes cause cast formation.

Hyaline Casts Appearance

Transparent, cylindrical with parallel sides and rounded ends; seen more when urine flow is slow and proteinuria is high, less in alkaline urine.

Hyaline Casts Clinical Implications

Casts formed from protein leakage through damaged glomerular membranes, indicating conditions like nephritis, chronic renal disease, or diabetic nephropathy.

Granular Casts vs Hyaline Casts

Granular casts are renal casts that contain granules and indicate damage to the renal tubules, whereas hyaline casts are clear, homogeneous structures that can be found in normal urine or in cases of dehydration and concentrated urine.

Fine vs Course Granules

• fine: appear grey or pale yellow in color)

• coarse: appear as darker

Granular Casts

Degenerated cellular components or aggregated serum proteins within Tamm-Horsfall mucoprotein, indicating significant renal disease.

Granular Cast Under Phase Contrast

Granular Cast Clinical Significance

may be seen in:

• Acute tubular necrosis

• Advanced granulonephritis

• Pyelonephrities

• Malignant nephrosis

• Chronic lead poisoning

Cellular Casts

when concentrated proteins in the distal tubule entrap cells, leading to Hyaline Casts with cellular inclusions → WBC Casts. Mucus threads found in urine samples can indicate irritation or be a normal finding.

WBC Casts

• Formed by aggregates of WBCs trapped in protein matrix in the renal tubular lumen.

• An excess of WBCs singly or in clamps, in the urine may indicate inflammation

• of renal origin

• seen in acute pyelonephritis and occasionally in glomerulonephiritis.

RBC Casts

• Usually, they found in hematuria

• brown to almost colorless

• usually diagnostic of glomerular diseases.

• Normal range: normally not seen in normal individual

• Formed usually after accumulation of cellular element in the renal tubules

RBC Casts Appearance

clear membranes and lack nuclei, formed from RBCs trapped in renal tubules. Mucus threads present but difficult to see

Waxy Casts (Renal Failure Casts)

• Not seen in normal individuals.

• shorter and broader than hyaline casts.

• Composed of homogeneous, yellowish materials.

• May occur from cells (WBC, RBC, or Epithelial) casts, hyaline casts.

Waxy Casts are found in what possible diseases?

• Chronic renal disease

• Tubular inflammation

• degeneration/Localized nephron

• obstruction/malignant hypertension

• presence indicates severity of renal disease.

Fatty Casts

• normally not seen in health individuals.

• contain fat droplets inside them.

• formed after accumulation of fat in the tubular vessels, especially tubular epithelial and finally disintegrated.

• fat droplets, oval, fat bodies, or fat casts → nephrotic syndrome.

• Chronic renal disease/Inflammation and degeneration of renal tubules/ lupus and toxic renal poisoning

Epithelial Casts

• consist mainly of desquamated tubular epithelial cells

• appear as two rows of cells in a protein matrix.

• A large number indicates renal parenchymal disease with tubular damage.

Procedure for Microscopic Examination - Key Steps

1. Centrifuge: Centrifuge urine (1500-2000 rpm, 3-5 minutes).

2. Discard Supernatant: Remove the liquid (supernatant).

3. Resuspend Sediment: Mix the remaining sediment.

4. Prepare Slide: Place a drop of sediment on a slide and cover.

5. Microscopy: Examine under 10x, then 40x objective.

Source of Errors During Microscopic Examination of Urine

• Drying of specimen on the slide.

• Improper pouring off of supernatant decreases sediment concentration, leading to false results.

• Discarding whole sediment with supernatant can cause false negatives.

• Collect another sample and repeat test if errors occur.

Microscopy Types and Key Findings

• Bright Field: Frequently used, low light via rheostat control not lowering condenser

• Phase Contrast: Advantageous for low refractive casts, mucous threads and Trichomonas

• Polarizing: Crystals and lipids: confirm fat droplets, oval fat bodies and fatty casts

• Interfering Contrast: 3D image – fine structures

• Dark-Field: spirochete Treponema pallidum

• Fluorescence: immunofluorescence

Classification of Urinary Sediments

• Organized (Formed)

  • Ex in HPF: WBCs, RBCs, Bacteria

  • Ex in LPF: Muscus, casts, yeast cells, miscellaneous

• Non-Organized (Non-Living Material)

  • Slightly Acidic Crystal

  • Acidic, Neutral, or slightly alkaline

  • Alkaline, Neutral, or slightly acidic

RBCS in Urine

• organized urinary sediment

• NOT usually present in normal urine 0-5/HPF

• Appearance:

  • fresh sample: intact, small and faint yellowish discs, darker at the edges

  • RBCs will lyse in acetic acid while other elements will stay intact.

RBC Variations in Urine

• In conc. (hypersthenuric) urine: RBCs may be crenated and small

• In diluted (hyposthenuria) urine: RBCs may be turgid, large, and may lyse.

• In alkaline urine: small or destroyed, forming brownish granules.

• In diluted and alkaline urine: RBCs rupture, releasing hemoglobin, forming 'ghost' cells (colorless cell membranes).

• Dysmorphic RBCs: vary in size, show protrusions or fragments.

To get rid of RBC’s so that WBC’s are more visible – acetic acid is very helpful, Why?

RBCs will lyse in acetic acid while other elements will stay intact.

Microscopic Examination of RBCs

OCCURS AT 40X OBJECTIVE

• presence of a few is normal

• higher numbers are indicator of renal disease

• result of bleeding at any point in urinary system

Clinical significance of RBCs in Urine

An elevated RBC count (typically exceeding 5 RBCs/HPF, averaged over 10 HPFs) may indicate:

• Macroscopic hematuria: TNTC (>100/hpf)

• Disease conditions in the urinary tract

Too many RBC = presence of disease conditions in the urinary tract, such as

• Acute and chronic glomerulonephritis

• Tumor that erode any part of the urinary tract

• Renal stone

• Cystitis

• Prostates

• Trauma of the kidney

• traumatic catheterization

Yeast Cells compared to RBCs

smaller and are oval in shape flattened, vary considerably in size with one specimen, and have budding at the surface

Bubbles (oil droplets) compared to RBCs

vary considerably in size and are extremely refractive or shiny → polarizing microscopy to find Maltese Shaped Cross

Leukocytes compared to RBCs

larger and have granular appearance upon addition of 2-5% acid the RBCs will disappear

Interfering factors for RBCs

Factors that may result falsely in high number of RBCs, i.e. without the presence of actual renal or other normal physiological disturbances included:

• Menstrual bleeding, Vaginal bleeding, Trauma to peranal area in female patients

• Following traumatic cateterization

• Some drugs:

  • Aspirin ingestion or over dose

  • Anticoagulant therapy over dose

Leukocytes (WBCs)

• Normal range: 0-4 WBC/HPF.

• Appearance: normally, clear granular disc shaped, the nuclei may be visible.

• In alkaline urine, they may increase their size and become irregular.

• Predominantly, polymorph nuclear neutrophils are seen

WBCs (Pus Cells)

occur due to predominance of neutrophils and the occurrence of bacterial cells together with polymorphonuclear cells, WBCs are called pus cells → may be seen in clumps.

Microscopic Examination of WBCs

Occurs at 40X OBJECTIVE; a few are normal while high numbers indicate inflammation or infection somewhere along the urinary or genital tract

WBCs Result Reporting

under 40x objective, at least 10 fields of microscope

• 0-5/HPF → normal

• 5-10/HPF → few leukocytes/HPF

• 10-20HPF → MOD/HPF

• 20-30/HPF → MANY/HPF

• Above 30 leukocytes/HPF →full/field

Clinical significance of leukocytes

Increased number of leukocyte urine are seen in case of:

• UTI such as renal tuberculosis

• All renal disease

• Bladder tumor

• Cystitis

• Prostates

• Temporarily increased during:

  • Fever

  • After strenuous exercise

Epithelial Cells

• Squamous epithelial cells

• Transitional epithelial cells

• Renal tubular epithelial cells

• Oval Fat Bodies

• Clue Cells

Order of Epithelial cells from smallest to largest

1. Renal tubular epithelial cells

2. Transitional epithelial cells

3. Squamous epithelial cells

Squamous Epithelial Cells

• large, flat cells with small nuclei

  • nucleus is usually distinct & centered

• Appear flat with abundant cytoplasm

• Originate from the superficial lining of the vagina, female urethra, and lower portion of the male urethra

• Common contaminant; seen in female voided specimen

Clue Cells

Squamous epithelial cells covered with coccobacilli, Gardnerella vaginalis

Transitional Epithelial Cells

• Shape: Polyhedral; swells to spheroidal in urine.

• Appearance: Round/pear-shaped contours, small central nucleus (may be bi-nucleated).

• Origin: Transitional lining of renal pelvis, ureter, urinary bladder.

• Normal: Few in urine; large clumps may suggest carcinoma.

Renal Tubular Epithelial Cells (RTE)

• Origin: Proximal and distal convoluted tubules

• Shape: Single, oblong or egg-shaped

• Appearance: Coarsely granular eosinophilic cytoplasm

• Nuclei: Small, dense chromatin (may be multiple)

• Clinical Significance: Indicative of acute tubular necrosis, drug, or heavy metal toxicity

What are RTEs associated with?

Presence of more than 2 RTE/HPF indicates tubular injury

• Usually seen in association with proteins or casts

• Clinical significance: increased amts indicative of necrosis of the renal tubules.

Clinical significance of Epithelial Cell Presence

• Presence of epithelial cells in large number, mostly renal types may indicate:

  • Acute tubular damage

  • Acute glomerulonephritis

  • Silicate overdose

TRUE OR FALSE: The presence of large # of epithelial cells with large # of Leukocytes and mucus trades (filaments) may indicate Urinary Tract Infections (UTI).

True, as this presence suggests inflammation and potential infection.

Oval fat bodies

• RTE absorb lipids present in filtrate

• Make RTE highly refractile

• Seen with free floating fat droplets

• ID with stain: Sudan III or Oil Red O

• Polarizing light: maltese cross

• Extremely significant finding. Seen in lipid nephrosis and terminal kidney disease.

What disease is associated with Oval Fat bodies in urine?

Lipiduria frequently associated with damaged glomerulus due to nephrotic syndrome

Reporting of epithelial cells

under 10X objective, semi-quantitatively

• 1-3/LPF

• 2-4/LPF

• 6-14/LPF

• 15-25/LPF

• Full Field/LPF

Bacteria

Normally not present in the urine

• Unless sterile collection a few may be non-pathological→Contamination

• Multiply rapidly in room temp conditions – increase pH

• Accompanied by WBCs significant for UTI (lower or upper)

• Motility (Trichomonas)

Yeast Cell

• fungi that are not normally seen in healthy individuals.

• Appearance

  • Variable in size

  • Colorless.

  • Oval in shape, and usually form budding

  • Have high refractive index.

  • Usually confused with RBCs

Branching Pseudohyphae

obscure specimen features & may indicate that the specimen is not a clean catch

• candida species (candida albicans)

  • UTI

  • Vaginites

  • DM

  • Intensive antibiotic or immunosuppressive therapy

Why are yeast cells found in specimens with high glucose levels? What does it indicate?

because they thrive in environments with abundant sugar, indicating a possible underlying issue such as diabetes or a UTI

Parasites

• Trichomonas vaginalis

• Schistosoma haematobium

• Wuchereria bancroftie

• others such as Entrobious vermicularies also may occur due to contamination of the urine with stool.

Trichomonas Significance in urine

• small parasite that is very active in a fresh specimen

• multiple flagella as well as an undulating membrane = MOTILE

• absence of movement → mistaken for WBCc

Spermatozoa - Miscellaneous

Small, motile structures with a head and tail, often seen in the urine of males and occasionally in females after coitus.

Mucus

• Protein material: Tamm-Horsfall protein

Appears as thread like structures (HPF)

Contaminates and Artifact Structures

• Muscle fibers

• Vegetable fibers

• Air pockets or bubbles

• Pollen greens

• Starch granules

Urine Sediments: Artifacts, Crystals, Mucus

Crystals in Sediment

• precipitation of solutes

• are not normally present in freshly voided urine

• can precipitate on storage

• most are not clinically significant

• pH critical to differentiating some important crystals

Acidic Urine Includes…

All clinically significant crystal are found in acid urine

• Include: cystine, tyrosine, leucine & iatrogenic crystals: sulfonamide & ampicillin

• Amorphous Urates

Amorphous Urates

• Non crystalline urate salts of Na, K, Mg, & Ca

• small & yellow-brown granules and can be in acidic or neutral urine

• Will dissolve in alkaline or when heated

  • If add acetic acid, uric acid crystals will precipitate out

Amorphous Urates vs Amorphous Phosphates

Amorphous urates are non-crystalline urate salts, small yellow-brown granules found in acidic or neutral urine, whereas amorphous phosphates are non-crystalline forms of calcium and magnesium phosphates that typically occur in alkaline urine.

Uric Acid Crystals

• Urine pH = 5.0 to 5.5

• Common form = diamond shape but may be cube shaped or cluster in rosettes

• Usually yellow to orange-brown

• Are birefringent under polarizing light

When do Uric Acid Crystals appear?

appear normally BUT can see large #s in gout & in increased purine metabolism such as cytotoxic drugs

What are the two forms that Oxalate Crystals appear as?

Both colorless

• Dihydrate Form:

  • 2 pyramids / squares w/ intersecting lines

• Monohydrate Form:

  • small ovoid or dumb bell

Calcium oxalate Dihydrate Form

Usually octahedral or look like envelope, less common than monohydrate form although both are seen in kidney stones

Calcium oxalate Monohydrate Form

A birefringent, colorless crystal that varies in size, often seen in neutral or acidic urine. It can appear due to normal dietary intake (e.g., ascorbic acid, tomatoes, spinach) and also indicates ethylene glycol.

Bilirubin Crystals: Abnormal State

• Appear as fine needles, granules, or plates

• urine is acidic

• always yellow-brown

• the bile stains the other components of the sediment

• presence of the crystals indicate high concentrations of bilirubin in the urine

What is the next step when bilirubin crystals are suspected in urine?

Confirm the presence of bilirubin with a strip reaction; positive results indicate a pathological process and abnormal crystals, often associated with liver disease.

Amino Acid Crystals and Pathology

Amino acid crystals are ALL ABNORMAL & seen in overflow aminoaciduria

• can be seen in rare cases of liver disease, more likely to reflect inherited metabolic disorder

• Include: TYROSINE, LEUCINE, AND CYSTINE

Tyrosine Crystals

• fine, delicate needles, colorless or yellow

• frequently in clusters or sheaves [as in stacks of wheat]

• in acidic urine

• less soluble than leucine, so found more often

Leucine Crystals

• Highly refractile yellow to brown spheres in acid urine.

• Have concentric/radial striations on their surface

• Can be mistaken for fat globules [or vice versa]

  • will not stain with fat stains or appear as maltese cross under polarization

Cystine Crystals

• Colorless hexagonal plates

• sides may be uneven

• primarily seen in acidic urine

• Clincally significant, seen in congenital cystinosis or cystinuria

  • Deposit out in tubules as calculi/stone causing damage

Why are Cystine Crystals confused with Uric Acid Crystals? How do we confirm Cystine Crystal presence?

both may present as hexagonal shapes. To confirm cystine crystal presence, perform cyanide-nitroprusside test using SODIUM CYANIDE which will yield a positive result for cystine (purple color)

Cholesterol Crystals

• Clear flat rectangular plates with notched corners

• in acidic urine

• Rarely seen

• Presence indicates both ideal conditions for precipitation & supersaturation

When are Cholesterol Crystals commonly seen?

• Always see with positive protein + fat droplets, fatty casts or oval fat bodies

• Seen in nephrotic syndrome & other renal damage

Ampicillin Crystals

• Appear in acidic urine

• Require large dosage for formation, so rarely seen

Calcium Phosphate Crystals

Colorless, thin, star-shaped prisms with one tapered end; they often appear as irregular granular sheets resembling degenerating squamous epithelial cells.

Sulfonamides Crystals

• Highly refractile & birefringent

• In acidic urine

• Closely resemble ammonium biurate but differentiated on

  • pH & solubility

  • chemical confirmatory test

• Type varies with form of drug prescribed

• rarely seen due to recent solubility of sulfa drugs

Alkaline Urine Crystals

• Amorphous Phosphate

  • precipitate white rather than pink-orange of amorphous urate

  • presence enhanced by refrigeration

• Triple Phosphate

  • most common are 3 & 6 sided ‘coffin lids’, vary in size

Amorphous Phosphate

• alkaline or neutral urine

• microscopically not distinguishable from amorphous urates

  • distinguishable on urine pH & solubility

  • precipitate white rather than pink-orange of amorphous urates

  • are soluble in acid & will not dissolve when heated to 60C

• presence enhanced by refrigeration

Triple Phosphate Crystals

• Colorless & in different forms

  • most common are 3 & 6 sided ‘coffin lids’

  • vary greatly in size

  • may also see a ‘fern leaf’ form, feathery

• See in normal healthy individuals but are often present in formation of calculi

  • are associated with UTI

Ammonium Biurate

• Yellow brown spheres with striations

• Can have irregular spicules ‘thorny apple’

• In alkaline or neutral urine

• Not significant unless seen in fresh urine

• Usually seen in old specimens

• Dissolve in acetic acid or heating to 60C

Calcium Carbonate

• Very small granular crystals

• Can be misidentified as bacteria

• Usually found in pairs ‘dumbbell shape’

Acidic Urine (pH < 7) Crystals

• Amorphous Urates

• Uric Acid

• Calcium Oxalate

• Bilirubin

• Tyrosine

• Leucine

• Cystine

• Cholesterol

• Sulfonamides

• Ampicillin

Alkaline Urine (pH > 7) Crystals

• Amorphous Phosphates

• Triple Phosphate

• Ammonium Biurate Crystals

• Calcium Phosphate Crystals

• Calcium Carbonate Crystals

What crystal can appear in acidic AND neutral pH?

Calcium Oxalate Crystals

Clinical Significance of Crystals

• kidney stone formation: Calcium oxalate, Uric acid, Cystine, Triple phosphate

• metabolic disorders: Cystine, Tyrosine, Leucine

• liver disease: Bilirubin, Tyrosine, Leucine, Cholesterol

• UTI: Triple phosphate

• drug therapies: Sulfonamides, Ampicillin

• benign: Amorphous urates, Amorphous phosphates

Shapes of Crystals

• Envelope-shaped = Calcium oxalate dihydrate

• Needle-shaped = Uric acid, Bilirubin, Tyrosine, Sulfonamides, Ampicillin

• Hexagonal = Cystine

• "Coffin lid" = Triple phosphate)

• "Thorny apple" = Ammonium biurate

• Rhombic = Uric acid

• Spherical = Leucine