Laboratory Urinalysis

Laboratory urine analysis

Microscopy

  • Uncentrifuged specimen
  • Examine for red cells, white sells and epithelial cells
  • Pyuria (>10 x 106 /L) indicative of the presence of inflammation
    • Pyuria is usually, but not always associated with significant bacteruria
    • White cells can be associated with non-infectious conditions such as calculus, renal disease, trauma and neoplasia

Casts

  • Plugs of High MW mucoprotein form in the renal tubules and collecting ducts by agglutination of protein cells or cellular debris and flushed loose by urine flow
  • Hyaline
    • Normal if present in small amounts
    • Inflammation, trauma to glomerular capillary, renal parenchymal disease
    • Epithelial
      • Eclampsia, amyloidosis, heavy metal poisons
      • Renal tubular damage and nephrosis
      • Granular
        • Coarse or fine
        • Lead poisoning, ARF, CRF, PN
      • Fatty/waxy
        • Nephrotic, diabetes, CRF
      • RCC
        • GN, SLE, SBE, renal infarction
        • Malignant HT, collagen disease, sickle cell
      • WCC
        • Acute PN and GN
        • Lupus nephritis
      • Drugs
        • Contrast, amphotericin, isoniazid, frusemide, penicillin, sulphonamides, gentamicin, Bactrim

Culture

  • Urine in the bladder is normally sterile
  • In process of specimen collection contamination from urethra and periurethral areas is common
  • Count significance (Significant bacteruria)
  • Must take age, sex, clinical history into account
  • Generally accepted that >108 bacteria per litre is indicative of significant bacteruria
  • PPV >98%
  • NPV < 65%
  • 33% of acutely symptomatic females have bacterial counts below this (significant bacteruria taken as 105 in these people)

Sensitivity and specificity of microbiology tests



Critical Care

Compendium

Associate Professor Curtin Medical School, Curtin University. Emergency physician MA (Oxon) MBChB (Edin) FACEM FFSEM Sir Charles Gairdner Hospital.  Passion for rugby; medical history; medical education; and asynchronous learning #FOAMed evangelist. Co-founder and CTO of Life in the Fast lane | Eponyms | Books | Twitter |

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