Updated: 8/23/2017

Urinalysis

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Snapshot
  • A 22-year-old woman presents with dysuria, pyuria, and increased urinary frequency. She reports her symptoms began approximately 2 days prior to presentation. She has had similar symptoms 5 months ago. She is sexually active and uses condoms inconsistently. Physical examination is unremarkable. Urinalysis is positive for pyuria and bacteruria. Urine culture demonstrates ≥ 100,000 colony forming units (CFU) /mL. (Urinary tract infection)
Introduction
  • Process
    • a fresh urine specimen is obtained and subsequently centrifuged
      • the supernatant is placed in a separate tube
        • a urine dipstick is placed in the supernatant to analyze for
          • pH
            • normal is between 5-6.5
            • clinical correlate
              • urine pH >7.5 can suggest a urinary tract infection (UTI) secondary to urea-splitting microbe
          • glucose
            • clinical correlate
              • urine glucose can be detected in the urine in poorly controlled diabetes mellitus
          • ketones
            • clinical correlate
              • urine ketones can be seen in poorly controlled diabetes mellitus
          • nitrite
            • clinical correlate
              • can be a reasonably good screening test for UTI
          • heme
            • clinical correlate
              • typically indicative of blood in the urine
                • however, the urine can be heme positive in the setting of intravascular hemolysis and rhabdomyolysis
          • protein
            • clinical correlate
              • elevated protein in the urine can suggest a nephrotic syndrome
        • specific gravity
          • reflects the weight of a solution compared to the weight of distilled water
            • the solution and distilled water must be of equal volume
            • when the urine contains large solutes (e.g., glucose) the specific gravity increases
        • urine osmolality
          • measures the amount of dissolved particles per unit of water found in urine
      • the sediment should be resuspended and then transferred to a slide for analysis
        • urine casts
          • these represent protein and cell precipitates generated within the tubular lumen
        • red blood cells (RBCs)
          • red cell morphology
            • dysmorphic RBCs
              • suggests glomerular bleeding
            • round and uniform RBCs
              • suggests extrarenal bleeding (e.g., ureter and bladder)
        • white blood cells (WBCs)
          • seeing WBCs in the urine is termed pyuria and suggests an infection or inflammatory process in the urinary tract
          • neutrophils are more commonly seen
            • eosinophiluria can be see in drug-induced acute intestitial nephritis
        • epithelial cells
        • crystals
 
Urine Casts
Casts
Associated Conditions
RBC casts
  • Glomerulonephritis
  • Vasculitis
  • Malignant hypertension
WBC casts
  • Tubulointerstitial inflammation
  • Acute pyelonephritis
  • Transplant rejection
Fatty casts
  • Nephrotic syndrome
  • "Maltese cross" sign
Granular casts
  • Acute tubular necrosis
Waxy casts
  • End-stage renal disease
  • Chronic renal failure
Hyaline casts
  • Non-specific
 

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