Microscopic Examination of Urine – Lecture 1 & 2

Flashcards cover specimen handling, microscopy techniques, stains, cellular elements, casts, crystals, artifacts, and introductory renal disease concepts from Lecture 1 & 2 on urine microscopic examination and renal disorders.

What specimen volume and centrifugation settings are recommended for routine urine sediment preparation?

Centrifuge 12 mL of urine at 400 RCF for 5 minutes.

After centrifugation, how much sediment is placed on the glass slide and what size cover slip is used?

Transfer 20 µL (0.02 mL) of sediment to a slide and cover with a 22 × 22 mm cover slip.

When should urine sediment be examined without centrifugation?

When less than 3 mL of urine is available.

Which microscope objective is first used to detect casts in urine sediment?

The low-power objective (LPO, 10×).

State the calculation used to convert revolutions per minute (RPM) to relative centrifugal force (RCF).

RCF = 1.118 × 10⁻⁵ × radius (cm) × RPM².

What does the Addis count quantitatively measure and what is the required specimen?

Quantitates formed elements (RBCs, WBCs/ECs, hyaline casts) in a 12-hour urine specimen preserved with formalin.

Give the normal Addis count values for RBCs, WBCs/ECs, and hyaline casts per 12-hour urine.

RBCs 0–5 000; WBCs/ECs ≤ 1 800 000; Hyaline casts ≤ 5 000.

Which microscopy technique enhances visualization of low-refractive-index elements like casts and shows a 'halo'?

Phase-contrast microscopy.

What is birefringence, and which microscopy technique detects it?

Birefringence is the ability to refract light in two directions at 90°; detected by polarizing microscopy.

For what organism is dark-field microscopy routinely used in urinalysis labs?

Treponema pallidum (spirochetes).

Name two interference-contrast microscopy types that give 3-D images.

Nomarski (differential interference) and Hoffman (modulation contrast).

Which supravital stain is most commonly used for general urinary sediment and what does it accentuate?

Sternheimer-Malbin (crystal violet + safranin O); delineates cell nuclei and cytoplasm, highlights WBCs, epithelial cells, casts.

What stain differentiates WBCs from RTE cells by enhancing nuclear detail?

Toluidine blue (supravital).

Which stain lyses RBCs but leaves WBC nuclei intact, aiding RBC/WBC differentiation?

2 % acetic acid.

Which lipid stains color triglycerides and neutral fats orange-red?

Oil Red O and Sudan III.

What stain is used to detect urinary eosinophils?

Hansel stain (eosin Y + methylene blue).

List the normal microscopic reference ranges for RBCs and WBCs in urine.

RBCs 0–2/HPF; WBCs 0–5 (or up to 0–8)/HPF.

How do RBCs appear in hypertonic versus hypotonic urine?

Hypertonic: crenated/shrunken; Hypotonic: ghost cells (lysed).

Describe 'dysmorphic' RBCs and their clinical implication.

RBCs with projections or fragmentation indicating glomerular membrane damage.

What are 'glitter cells' and when do they appear?

Swollen neutrophils in hypotonic urine whose granules exhibit Brownian movement and sparkle.

An eosinophil count >1 % of urinary WBCs is associated with which condition?

Acute interstitial nephritis (commonly drug-induced).

Identify the epithelial cell type: largest, abundant irregular cytoplasm, prominent nucleus, originates from the vagina and lower urethra.

Squamous epithelial cell.

What are 'clue cells' and what organism covers them?

Squamous epithelial cells coated with Gardnerella vaginalis; indicate bacterial vaginosis.

Which epithelial cells line the renal pelvis to bladder, become elevated after catheterization, and may form syncytia?

Transitional (urothelial) epithelial cells.

Which urinary epithelial cell type is most clinically significant and what does >2 cells/HPF indicate?

Renal tubular epithelial (RTE) cells; >2 RTE/HPF indicates tubular injury.

Define an oval fat body and state two ways to confirm its identity.

An RTE cell containing lipid droplets; confirm with lipid stains (Oil Red O/Sudan III) or polarizing microscopy (Maltese cross cholesterol).

Which bacteria group most commonly causes UTIs and what urinalysis correlates support bacterial infection?

Enterobacteriaceae (e.g., E. coli); correlate with positive nitrite, leukocyte esterase, alkaline pH, and WBCs.

Presence of bacteria without WBCs in urine suggests what?

Specimen contamination or prolonged standing/unpreserved urine.

Name the most common parasite seen in urine and its characteristic movement.

Trichomonas vaginalis; exhibits pear-shaped jerky motility.

What microscopic finding is reported as 'threads' and is primarily composed of Tamm-Horsefall protein?

Mucus threads.

How many microscopic fields are averaged when quantitating urinary elements?

Ten representative fields.

Give the reporting scale words for non-numeric quantitation (e.g., epithelial cells per LPF).

'None, Rare, Few, Moderate, Many'.

Define cylindruria.

Excretion of urinary casts.

Where in the nephron are most casts formed and what protein forms their matrix?

Distal convoluted tubule and collecting ducts; Tamm-Horsefall (uromodulin) protein.

List three conditions that promote cast formation (protein gelling).

Urine stasis (low flow), acidic pH, presence of Na⁺ and Ca²⁺ ions.

Describe a hyaline cast and give one physiologic and one pathologic cause.

Colorless, translucent prototype cast; physiologic—strenuous exercise; pathologic—glomerulonephritis.

Which urinary cast appears orange-red, is fragile, and indicates bleeding within the nephron?

RBC cast.

What is the clinical significance of WBC casts?

Infection or inflammation within the nephron, especially pyelonephritis or acute interstitial nephritis.

Why are pseudoleukocyte casts not reported as true casts?

They are merely clumps of leukocytes formed in the lower urinary tract, lacking a Tamm-Horsefall matrix.

Granular casts originate from what source and what appearance distinguishes ‘fine’ granularity?

Lysosomal breakdown of RTE cells; fine granules give a sandpaper appearance.

Which cast type contains fat droplets, correlates with nephrotic syndrome, and shows Maltese crosses under polarizing light?

Fatty cast.

What characterizes a waxy cast and with what renal condition is it associated?

Highly refractile, ground-glass appearance with blunt or jagged ends; indicates chronic renal failure or severe urine stasis.

Define a broad cast and explain its nickname.

A cast 2–6 × wider than typical, formed in dilated tubules; called 'renal failure cast'.

Which cast is identified by Gram stain and signifies pyelonephritis?

Bacterial cast.

What three urine factors influence crystal formation?

pH, solute concentration, and temperature.

Which normal acid crystal produces a ‘brick-dust’ pink sediment macroscopically?

Amorphous urates.

Describe the classic shape of uric acid crystals.

Rhombic/diamond or four-sided flat plates (‘whetstones’).

What is the most common urinary crystal overall and what two shapes does it exhibit?

Calcium oxalate; dihydrate forms envelopes/pyramids, monohydrate forms ovals/dumbbells.

Which normal alkaline crystal appears as 'coffin-lid' prisms?

Triple phosphate (magnesium ammonium phosphate, struvite).

Name the abnormal acid crystal that is hexagonal, colorless, and diagnostic for an inherited amino-acid transport disorder.

Cystine crystal (seen in cystinuria/cystinosis).

How can cholesterol crystals be distinguished from radiographic dye crystals?

Review patient imaging history and note very high specific gravity (>1.040) with radiographic media.

Which paired amino-acid crystals indicate severe liver disease and describe their appearance.

Tyrosine: fine needles in sheaves/rosettes (yellow); Leucine: yellow-brown spheres with concentric rings and radial striations.

Sulfonamide crystals are differentiated from calcium phosphate by what simple chemical test?

Calcium phosphate dissolves in dilute acetic acid; sulfonamides do not but give positive lignin and diazo tests.

Name two drug-related crystals that form needle bundles after high-dose therapy or refrigeration.

Ampicillin and acyclovir crystals.

What stain provides a positive Rous test for hemosiderin granules in urine?

Prussian blue stain.

Which artifact shows a Maltese-cross appearance under polarizing light yet is not pathologic?

Starch granules (from gloves or powders).

Identify four common urinary sediment artifacts that may mimic true elements.

Starch granules, oil droplets, air bubbles, pollen grains, and fibers/hair.

Give two immune mechanisms that commonly underlie glomerular disorders.

Deposition of immune complexes (IgG, IgA) and complement-mediated damage to basement membrane/capillaries.

List three non-immunologic causes of glomerular damage.

Chemical/toxin exposure, nephrotic syndrome, and deposition of amyloid or diabetic nephropathy.