You have been asked to provide a mid stream urine specimen and want to know how to do this (and why it needs to be mid stream).
Mid steam urine collection is used to diagnose a bladder or urinary tract infection. Urine does not normally contain any significant numbers of micro-organisms. However, it can become contaminated from bacteria or yeasts introduced into the urinary tract. The resulting infection causes symptoms of pain or burning during urination (called dysuria), an urge to pee frequently, and a cloudy, offensive smelling urine.
Most urinary tract infections (UTI’s) are caused by the bacteria Escherichia coli (E. coli). Other frequently identified bacteria are Proteus, Klebsiella, and Staphylococcus saprophyticus.
Why do they want the specimen?
Once a mid stream urine (MSU) is obtained, the laboratory technicians are able to count the number of white blood cells (pus cells) or micro-organisms such as bacteria or yeast (known as a colony count) under a microscope.
Laboratory technicians usually over-compensate for this sort of mundane work by leading action packed lives filled with skydiving and deep-sea free-diving and mixed martial arts. Then they come back to work, sit at their desk and count pus cells.
The presence of large numbers of these pus cells strongly suggest a UTI. Further tests are performed to ascertain any antibiotic sensitivities.
This is known as MC&S: or Micro, Culture and Sensitivity, and lets the doctor prescribe the most likely effective antibiotic if required.
Once collected, the specimen is incubated at body temp for 24hrs on agar plates and re-examined.
If the inoculated plates remain negative for significant growth the specimen culture is considered negative.
The theory is that by catching the mid section of the urine flow, you obtain a specimen that has not been contaminated by bacteria colonising the end of your urinary tract, as these are all washed clear by the initial flow.
Logically, a stronger flow is going to provide a more effective ‘wash’, so the best time to obtain an MSU is when the bladder is full.
Why the rush?
The specimen should be sent to the lab as soon as as possible (ideally within 30 min) after collection. Urine is an excellent culture medium for any bacteria or micro-organisms that are present. Especially if left standing in a warm environment. This can lead to false positive results.
If the specimen cannot be sent straight away it will be refrigerated at around 4 degrees Celsius. At this temperature an accurate analysis can be made for up to 4–6 hours.
How to provide an excellent MSU:
Stuff you should be given to collect your MSU.
- Some gauze and saline to clean yourself with. A collection container (usually this has a yellow screw-top lid).
This is what you need to do:
- Wash your hands BEFORE going to the toilet.
- Before passing urine, use the small saline soaked gauze, to clean yourself with.
- If male clean your penis from TIP to BASE. If you have a foreskin retract it and clean this area too.
- If female, clean genitals from FRONT to BACK and from inside to outside.
Cleaning of the genital area before collecting an MSU has been found to make little difference in contamination rates, however, the principles of good hand and genital hygiene should be observed anyway.
- Begin to pee into the toilet/bedpan/bottle
- Next, pause for a moment or, if you are unable to do this, just slide the collection container under to catch the mid stream specimen. Take care not to accidentally contaminate the specimen or touch the inside surfaces of the container.
- You will only need around 10 to 15 mls. Once collected place the collection container somewhere safe whilst you finish your pee.
- If the container you were given has a lid, carefully screw it on. Again, try not to touch the inside surfaces.
- Wash your hands.
Give the completed specimen to the staff who will label it with your identification details and send it to the lab.