urinalysis (UA)

Introduction

Also see:

• urine dipstick (1st step in urinalysis)
• 24 hour urine

Indications

• evaluation of urologic disease
  • urinary tract infection
  • proteinuria
  • glucosuria
  • ketonuria
  • hematuria
  • crystalluria
• pregnancy
• before & after invasive urologic procedure

Contraindications

• routine health surveillance in asymptomatic patients
• routine preprocedural urinalysis
• screening for urothelial cancer

Reference interval

microscopy

• WBC:
  • > 5 WBC/hpf in spun urine is considered abnormal
  • associated with infections or allergic reactions
• RBC: > 3 RBC/hpf is considered abnormal;
  • dysmorphic RBC (> 80%) indicate glomerular disease
  • blood in the absence of RBC suggests hemolysis vs rhabdomyolysis
• Eosinophils: Hansen's stain - interstitial nephritis
• Bacteria:
  • >1 bacteria/ hpf (oil) in unspun urine, or
  • >10 bacteria/hpf (oil) in centrifuged urine correlates with >10E5 colony forming units per mL on culture
• renal tubular epithelial cells
  • acute tubular necrosis (ATN)
  • acute interstitial nephritis (AIN)
  • heavy metal poisoning
• squamous epithelial cells
  • common in voided or catheterized samples due to urethral or vaginal contamination
• crystals
  • calcium oxalate
  • struvite (magnesium ammonium phosphate in basic pH often secondary to urea-splitting organism)
  • uric acid crystals
  • calcium phosphate crystals
  • tyrosine crystals are associated with liver disease
    • leucine crystals may occur with tyrosine crystals
• casts:
  • casts are cylindrical aggregates of uromodulin (Tamm-Horsfall glycoprotein) that trap WBC, RBC or non-cellular material within their lumen
  • WBC casts are suggestive of interstitial nephritis
  • RBC casts or urine acanthocytes are suggestive of glomerulonephritis or vasculitis
  • broad, muddy brown casts are associated with acute tubular necrosis (ATN)
  • hyaline casts: uromodulin alone (benign)
• maltese cross:
  • lipid droplets seen in polarized light suggest nephrotic syndrome or lipid-storage disease
  • lipids may appear as droplets, oval fat bodies or fatty casts

urine pH

• normal 4-7.5, 5.0-6.5
• diurnal variation
• pH > 7 suggests infection with urea-splitting organisms
• pH < 5.5 excludes RTA type I
• acidic urine
  • high protein diet
  • acidosis
  • K+ depletion
• alkaline urine
  • vegetarian diet (low acid ingestion)
  • alkalosis (unless K+ depleted)
  • urease-producing bacteria
  • postprandial alkaline tide
  • renal tubular acidosis

specific gravity

• reference inerval: 1.005-1.031 (50 - 1400 mOsm/kg)
• low with dilute urine
• high with concentrated urine, glycosuria or contrast agent

appearance

• turbid: phosphate, urate, RBC, WBC
• foam: protein (white), bilirubin (yellow)
• white: chile, phosphate, pus, elephantiasis
• yellow: urochrome
• blue green: methylene blue, Pseudomonas
• orange-red: bile, beets, pyridium, rifampin
• red-brown: hemoglobin, myoglobin, levodopa
• yellow which turn red: PAS

protein

• normal < 150 mg/day
• most renal parenchymal disease will manifest some degree of proteinuria
• tubular proteinuria rarely > 2 g/day
• nephrotic syndrome > 3.5 g/day
• test
  • colorimetric "stix"
    • false positives may occur with:
      • benzalkonium, chlorhexidine
    • false negatives may occur with immunoglobulin light chains (Bence-Jones protein)
    • trace to 1+ protein rarely significant
  • precipitation: sulfosalicylic acid
  • dye-binding: Coomassie brilliant blue
  • chemical
    • Biuret
    • Folin - Lowry
  • protein electrophoresis
• urine protein/creatinine ratio
  • a value 0.1 generally corresponds to 24 hour urine protein of < 100 mg/day

glucose

• glucosuria in the absence of hyperglycemia suggests proximal tubule dysfunction
  • SGLT-2 inhibitor

More general terms

• clinical laboratory test

More specific terms

• urine dipstick
• urine microscopy
• urine sediment

Additional terms

• urine chemistry test
• urine culture
• urine discoloration

Component of

• hypertension panel

Components

• collection duration of urine
• character of urine
• clarity of urine
• mucus in urine
• amorphous sediment in urine
• cells in urine
• appearance of urine
• urine color
• specific gravity of urine
• crystals in urine
• protein in urine
• urinary cast
• urinary indices

Patient information

urinalysis patient information