Fig. 24.1
Stone Cup Strainer (Courtesy of Advanced MedConnection, Inc.)
Depending on the size and shape of the stone, this may take a few hours, to several days or even as long as a few weeks. Drinking plenty of fluids enhances the chances for the stone’s passage from the kidneys to the urethra. It is important to continue to drink fluids and maintain hydration. The more fluids you consume, the more urine you will make and the more likely the stone will pass quickly out of your urinary tract system.
Once the stone is collected, your Urologist will send the stone for testing. This analysis reveals the composition of the kidney stone and enables your doctor to institute a plan to possibly prevent the formation of future stones. While straining the urine can be inconvenient, it is important to complete this task to make the appropriate diagnosis and aid in the treatment strategy. All stones fragments, no matter how large or small, should be collected and sent for stone analysis. This evaluation is essential and will shed light onto the etiology and pathogeneses of the renal stone so that therapy can be optimized. Remember….No strain, no gain!
24 hour Urine Test: The “World Series” of Urine Tests!
Obtaining a urine analysis for your physician is a test that will check for blood, bacteria, leukocytes and specific gravity of the urine. This is the equivalent of a regular baseball game. The 24 hour urine, however, is the grand test, where urine is collected for a continuous 24 hour period to determine all the factors responsible to determine potential causes of the patient’s stone. This, some may argue, is the World Series of urine tests!
Sometimes your urologist may need to know how much urine your body is producing in a day or how much of a particular substance (for example, calcium, sodium, potassium, creatinine or blood urea nitrogen) is eliminated in 24 hour. A single specimen urinalysis cannot provide this information, so patients are instructed to collect all of their urine produced in a 24 hour period. A special container is provided for this purpose, which is returned to the laboratory after you have finished the urine collection at home (see Fig. 24.2).
Fig. 24.2
24 hour urine container (Courtesy of Therapak)
The 24 hour urine will help your Urologist determine if your stone is related to diet, metabolic factors, or dehydration. Dehydration, for example is not how much fluid goes into the tank or body, but how the body mobilizes the fluid. So, for example, a patient who drinks ample amounts of fluids but sweats or has loose bowel movements that exceed his/her hydration, can become dehydrated and may be at risk for stones.
When Is the Appropriate Time for 24 hour Urine Test
Your urologist will determine when is the appropriate time for you to collect your 24 hour urine. Many times, if you are presenting with a symptomatic stone, your urologist will want to treat your stone first, followed by obtaining a 24 hour urine. This is done namely out of convenience for the symptomatic patient. For the patient with the asymptomatic stone, the 24 hour urine can be done right away. Likewise, for the patient with a known history of stones but not a current stone, who is undergoing preventive care, the urologist will determine the appropriate time for doing this test.
I always urge my patients to do their 24 hour urine test on a non-working day as they do not want to carry an orange jug around the office!
Preparation for the 24 hour Urine Test
Certain medications that you are taking may affect the test results of your 24 hour urine study. Your Urologist will determine which drugs to discontinue and which to continue during the test. Never discontinue medication without authorization from your physician.
A patient’s urine is a reflection of their eating habits. Therefore, individuals are encouraged to maintain their regular eating and drinking habits and not to artificially change their diet at the time of the study. If a patient is on a diet for specific health reasons, I ask the patient to continue these food choices, especially if this diet will be maintained. While this may represent a diet quite different from the regime contributing to their previous stone, it will help us learn if their current food choices are lithogenic and a potential cause for a future stone.
There are some factors that may influence the results of the 24 hour urine that may not be part of your normal daily activities or appropriate situations. These include heavy exercise, urinary tract infection, X-ray examination with contrast within 3 days prior to urine test and dehydration. Be certain to do this test at the right time and under the right circumstances.
How Do You Do the 24 hour Urine Test?
Urine is collected over a 24 hour period beginning with the second urine on the first day and ending with the first urine on the second day. After discarding the first urine of the day, all your further urine should be collected in the same container, including the first urine of the morning of the next day.
The 24 hour urine is certainly a way to keep you around the house. Being housebound, allows patients to obtain a complete specimen. Female patients can use a “graduated hat” for the collection of the urine.
Results of the 24 hour Urine Test
This 24 hour urine collection will be studied for chemicals in the urine that promote and inhibit stone formation. The specimen is analyzed for total urine volume, calcium, phosphorous, uric acid, creatinine, oxalate, magnesium, sodium, citrate, sulfur, urine pH, calcium oxalate supersaturation (SS CaOx) and uric acid supersaturation (SS UA). The urine test is helpful in identifying risk factor(s) for kidney stones. The most common cause for stones and the most common factor identified on the 24 hour urine test, for example, is a low total urine volume. Ideally, the test will verify that the patient is consuming enough fluid to minimize their risk for future stones. Patients must achieve a urine volume of 2 l/day.
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