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Instructions for the collection of a 24-hour urine sample

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.

• Begin the collection at the usual time that you awaken.
• At that time, pass your urine, flush it down the toilet and note the exact time. You will now have an empty bladder and an empty bottle. The collection of urine will start from this time.
• Collect every drop you pass during the day and night and finish the collection by passing urine at exactly the same time the next morning; You should add this final specimen to the bottle.
• The time you void the last urine specimen should not vary by more than 5 or 10 minutes from the time of starting the collection the previous day. If you have to urinate one hour before the appointed time, drink a full glass of water or more so that you can void again at the appropriate time. If you have to urinate 20 minutes before, hold the urine until the proper time. This is essential in order to accurately interpret the results of the test.
• You will now have a full first bottle, an empty bladder, and an empty second bottle. A second collection can be begun with the next voiding, following the same instructions. Similar instructions apply to a third collection.

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
October 2002