Urine microscopy and culture

Last updated: Sunday, 28, May, 2006

The item number and fee shown are for Australia only. The fee is the Medicare Schedule Fee. Laboratories may charge above this fee in some circumstances.  Please refer to: Group P10 - Patient Episode Initiation in the Australian Government Medicare Benefits at http://www.health.gov.au/pubs/mbs/

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Item Process
Specimen

Midstream or 'clean catch' urine, catheter or bladder aspirate specimen in a sterile container sent to the laboratory immediately, or refrigerated for up to 24 hours.

Method

Phase microscopy of uncentrifuged urine; quantitative cultures, specific identification of significant isolates, antibiotic susceptibility testing.

Application

Dysuria/frequency, cystitis, urinary tract infection, screening in pregnancy, post-partum fever, epididymo-orchitis, or unexplained fever.

Urine microscopy and culture may not be necessary before commencing treatment in simple urinary tract infections in young women.

Investigation of renal and urinary tract disease and renal involvement in systemic disease.

Interpretation

Cell count:
>10 x 106/L white cells suggests infection;
>10 x 106/L red blood cells indicates haematuria;
presence of dysmorphic red cells indicates glomerular origin;
>10 x 106/L squamous epithelial cells indicates skin/mucosal contamination of the sample.

Other microscopic findings:
red cell casts may be seen in glomerulonephritis;
white cell casts and mixed cell casts indicate renal disease; the presence of granular and/or hyaline casts, as an isolated finding, is of uncertain clinical significance. They may be seen in patients with dehydration.
Although crystals are seen frequently, they are not usually of any clinical significance.

Culture:
Infection can be diagnosed in symptomatic patients if bacterial colony count >106/L (pure growth).
The findings on microscopy should also be considered in interpretation.
Increased leucocytes and a pure culture favour infection, while increased squamous epithelial cells and mixed culture suggest contamination.
In patients without symptoms, 'asymptomatic bacteriuria' is defined as a colony count of ³106/L.
In catheter or bladder aspirate specimens any growth indicates infection.
Testing for antibacterial activity is commonly performed and will influence interpretation.

Reference

Ringsrud KM and Linné JJ. Urinalysis and Body Fluids. Mosby 1995.

Pezzlo M. Clin Microbiol Rev. 1998; 1: 268-280.