Urinalysis

Urinalysis

• Clean-catch midstream collection• Single straight catheterization• Suprapubic aspiration• Foley’s catheter• High osmolarity and low pH

– Cellular preservation– First voided morning urine*

Routine urinalysisGross exam Dipstick Microscopic•Color •pH •Cells•Turbidity •Sp gr •Casts•Odor •Protein •Bacteria

•Blood •Yeast•Glucose •Parasites•Ketones •Crystals•Leukocytes •Artifacts•Nitrites•Urobilibogen

Urinalysis: Odor

• Ammonia: bacterial contamination• Fruity: ketones (diabetes, starvation)• Maple syrup: maple syrup urine disease• Musty: phenylketonuria• Ingested foods: asparagus• Excreted drugs: antibiotics

Urine: physical properties

• Yellow (urochrome)• Clear• Specific gravity

– Inaccurate surrogate for osmolarity– 1.001-1.035 ~ 50-1000 mOsm/kg– 1.010 ~ “Isosthenuria”– Used to determine concentrating ability

Urine: chemical properties

• Dipstick methodology• pH: 4.5-8 • Protein: Trace = 5-20 mg/dL

1+ = 30 mg/dL2+ = 100 mg/dL3+ = 300 mg/dL4+ = >2000 mg/dL

• Blood: peroxidase activity of Hgb

Urine pH

• Normal range 4.5-8.5– pH > 7.5 : taking bicarbonate, alkali suppl– pH 8-9 : urea-splitting bacteria

• Acidosis with urine pH > 6.0, suggests RTA

• Amorphous crystal type depends on pH– pH 4.5-6.0: urates– pH >6.5: phosphates

• pH can rise in open container (CO2 loss)

Urine: chemical properties

• Glucose: • Ketones: Acetoacetate (++), acetone (+)

NOT β-hydroxybutyrate• Urobilinogen: Ehrlich reaction• Bilirubin: Only conjugated obstructive• Nitrite: Gm(-)bacteria convert Nitrate• Leukocytes:

Leukocyte esterase

• False Positive– Vaginal contamination

• False Negative– High glucose– Albumin– Ascorbic acid– Tetracycline– Cephalexin– Oxalic acid

Nitrite

• False negative– Inadequate bladder retention time (it may take

up to 4 hrs to convert nitrate to nitrite)– Prolonged storage of sample– Several uropathogens do not convert nitrate

to nitrite• Streptococcus faecalis, other gram positive

Microscopic examination

• “Spun” urine sediment• Centrifuge @ 1500-2000 rpm x 5 mins

Erythrocytes• Sources: Glomerulus

urethra• >2-3 rbc/HPF = pathologic• Crenated in hypertonic urine• Dysmorphic rbc’s ~ glomerular

pathology

Leukocytes• Larger than rbc• Nucleated cells/granules• Glitter cells (granules brownian motions)

Leukocytes

• R/O contamination• Mostly PMN’s, but also look for

Eosinophils• Staining for eosinophils

– Wright stain – Hansel stain (improves the

sensitivity and PPV)

Diseases Associated with Eosinophiluria

Urine Stain

N Hansel Wright

AIN 11 10 2

RPGN 10 4 4Postinfectious 6 1 1

ATN 30 0 0

Acute pyelo 10 0 0

Acute prostatitis

10 6 2

Nolan III RC et al: NEJM 1986;315:1516-19

Renal tubular epithelial cells• Larger than PMN’s• Few cells can be found in

normal urine• Indicate tubular damage or

inflammation from ATN or interstitial nephritis

Casts

…Tamm-Horsfall glycoprotein“Uromodulin”

RBC cast formation

Granular casts

• Fine granular casts– Serum proteins

• Coarse granular casts– Degeneration of embedded cells

• “Non-specific” but “pathologic”

CrystalsAcid Urine (pH<6) Alkaline Urine (pH>6)•Uric acid •Phosphates

Rhombic prism form Triple phosphatesSodium urate Calcium phosphatesAmorphous urate Amorphous phosphates

•Calcium oxalate •Ammonium urates•Cystine•Leucine•Tyrosine•Cholesterol•Sulfa

Oxalate crystals• Envelope-shaped• Dumbbell-shaped

Triple phosphate crystalsCoffin lid-shaped

Cystine crystals

Crystals due to drugs

Both are birefringent (strongly in Indinavir)

End