At the diabetes clinic we may ask you to obtain a collection of urine over a 24 hour period for the calculation of creatinine clearance and estimation of protein excretion or more rarely for 24 hour urinary catecholamine estimation in order to exclude a phaeochromocytoma.
The following are instructions for the proper collection of a 24-hour urine specimen. In some instances, you may be asked to collect three consecutive 24 hour urine specimens.
You should aim to collect every drop of your urine during the specified 24-hour period. It does not matter what the volume of the urine is, as long as it represents every drop that you pass. If you need to have a bowel movement, you must collect the urine separately. If unable to do so you should abandon the collection and start again on another day.
You can store the bottle at normal room temperature for a day or two, but ideally hand the sample in to the Laboratory at the Hospital or alternatively by prior arrangement to your doctors surgery.
The bottle should be kept cool or refrigerated for longer periods of time. The bottle contains a weak acid. If you get acid or urine from the bottle on your skin or clothing, rinse your skin or clothing immediately with plenty of cold water, and you will have no problem.
The laboratory will measure a substance called creatinine in your urine. This will help calculate the ‘creatinine clearance’ which will give us information about the function of your kidneys. It will also tell us whether each urine collection is complete. We cannot correct the result of an improper collection. We can only recognize that it is improper and disregard the result. This may mean that we have to repeat the test.
Important decisions regarding your treatment will depend entirely upon proper test results. It is most important that you make sure that your collections are complete.
Plan your collection for a day off or a weekend but if you plan to go out do take your collection bottle with you!
Finally, many people get their collection wrong despite the best of intentions. It is better to admit this and discard an improperly collected sample rather than hand in a partial sample which would yield an inaccurate result. This is wasteful of laboratory resources and also impacts on important decisions with regard to your treatment.
Dr Nishan Wijenaike, Consultant Physician
West Suffolk Hospitals Diabetes Service