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
References and Links
- Urine Color
- Urine Transparency (turbidity)
- Dipstick urinalysis
- CCC – Urinalysis
- Laboratory Urinalysis
- Urinalysis Overview Table
- Urine electrolytes – Urinary anion gap
Critical Care
Compendium
