Granulomatosis with polyangiitis ([GPA], Wegener’s) and microscopic polyangiitis (MPA) both cause blood vessel inflammation, which can lead to organ damage. The kidney is affected in 50% to 80% of patients with either GPA or MPA diseases.
How is kidney involvement detected?
One measure of kidney function is a blood test called the serum creatinine. A rising value indicates that the kidney has already experienced significant injury.
What is a urine dipstick test and why is it important?
Before serum creatinine rises, the first sign of injury is the presence of blood in the urine. Blood in the urine usually can’t be seen by the naked eye. A ‘urine dipstick’ is a simple device that can detect blood in the urine. The test is performed by the individual patient. Urine dipsticks are available over-the-counter at many drug stores.
If a patient with GPA or MPA has never had blood in their urine, finding it for the first time would be an important sign of early kidney involvement. Response to treatment is most effective and successful if kidney involvement is detected early, and especially before serum creatinine levels start to rise. Not detecting the first signs of kidney inflammation may lead to unrecognized kidney failure.
What are the benefits of using urine dipstick testing?
Using a urine dipstick is a practical approach for both patients and their doctors. By having the test done at home, patients won’t need to make frequent visits to their doctor’s office merely to have a urinalysis performed by urine dipstick. Also, doctors won’t need to examine urine under the microscope as frequently.
In what types of patients will urine dipstick testing be useful?
Performing a urine dipstick test is practical for:
- Patients with GPA or MPA who have never had blood in their urine. These patients should perform the urine dipstick test about once every 1 to 2 weeks.
If the test result is positive, the doctor should be called immediately. He or she will confirm that the test is positive or refute the results. (Sometimes there is an error in reading or interpreting the results.) If an abnormal result is found, the physician will look at the urine under the microscope to see if there are other signs of kidney inflammation. Serum creatinine would be obtained to determine if a change in kidney function has already occurred.
- Patients who have previously had kidney involvement and have subsequently done well and their urine has returned to normal. In these patients, the urine dipstick can be used as a monitoring tool.
For patients who have already have kidney disease, effective treatment may improve kidney function, but blood in the urine might persist for as long as a year and in some patients even longer. In this setting, the urine dipstick test taken by the individual patient may not be very helpful.
What else would be helpful to know?
Patients and doctors should know that there are many different causes of blood in the urine. Some examples include: urinary tract infection, kidney stones, or bleeding from a kidney cyst. None of these issues would be related to GPA or MPA and each would require a different approach than that provided for these diseases.
In brief, a dipstick test of the urine can be an extremely helpful diagnostic test -- performed by the patient -- to help guide the way to receive the best possible care.
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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. This document was last reviewed on: 9/24/2013…#10971