
Understanding your mid-stream urine (MSU) test results
A mid-stream urine (MSU) test is usually done to check for an infection in your bladder or kidneys.
When collecting the wee (urine), it's important to try to get a clean sample by following the instructions found in this factsheet.
Terms used
- Microscopy – what the lab sees looking at the wee under a microscope.
- Leukocytes (WBC) – white blood cells that your body makes to fight infections.
- Erythrocytes (RBC) – red blood cells that are usually only present in small amounts in your wee.
- Epithelial cells – skin cells.
- Culture – what the lab finds after trying to grow bugs (bacteria or fungi).
- Susceptibilities – if the bug will be affected by a particular antibiotic.
Results
- Leukocytes (WBC): <10 is normal, 10 to 100 is unlikely to be important, >100 is likely to indicate an infection.
- Erythrocytes (RBC): <10 is normal, 10 to 20 is unlikely to be important, >20 is abnormal.
- Epithelial cells: <10 is normal, >10 means the sample may be contaminated.
- Culture:
- No significant growth – means no infection was found.
- Mixed growth – means no single cause of infection was found.
- Growth of one bug, for example, E. coli, <100x106 – means the bug is present but may not be causing an infection.
- Growth of one bug, for example, E. coli, >100x106 – means the bug is likely to be the cause of an infection.
- Susceptibilities: Antibiotic name with "S" means the bug will be affected by that antibiotic. Antibiotic name with "R" means the bug will be resistant to that antibiotic.
Next steps
If your urinary tract infection (UTI) symptoms have improved, you will not need any further tests.
If you have ongoing symptoms such as pain or increased frequency of going to the toilet, contact your general practice team for advice. There may another cause for your symptoms.
If you have Leukocytes (WBC) in your urine but no growth from the urine culture, you may need to be checked for a sexually transmitted disease (STI).
If you continue to have blood in your wee (haematuria) after your infection has gone away, contact your general practice team as you may need further tests.
Written by HealthInfo clinical advisers. Page created April 2023.
Sources
The information in this section comes from the following sources, some of which may be clinically complex or not available to the general public
NHS North West Anglia – Guide to interpretation of urine microscopy results (https://www.cambridgeshireandpeterboroughccg.nhs.uk/_resources/assets/attachment/full/0/7479.pdf). Retrieved March 2023.
Royal College of Pathologists Australia – MCS Urine. Retrieved March 2023.
Image and embedded video sources
Doctor with sample container image from Shutterstock (image ID 1198665856). March 2023.
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Review key: HIUTR-269145