Testing for Pheochromocytoma

[as published in the VHL Family Forum, March 1996]

It is most important to test for pheochromocytomas before undergoing surgery for any reason, and before going through the childbirthing process.

While the authoritative test for a pheochromocytoma is a nuclear medicine scan called an MIBG, not everyone can get to a hospital that offers this test, and not everyone is a candidate for the test. The urine and blood tests for pheo are most reliable when care is taken in two areas -- diet prior to the testing, and preservation of the urine sample from the start of the test until the lab processing is complete.

[Editor's note: a new test for plasma free metanephrines is now considered to be more accurate and more specific for pheo than urine and blood tests for epinephrines.  See article "Finding Elusive Pheochromocytomas" in the December 1999 VHLFF.]

To get the best information from a 24-hour urine test, it is critically important that the patient -- that's you! -- follows carefully the pheo test instructions that go with the test. An informal survey of hospitals and VHL patients in my state discloses that not all hospitals provide these instructions to the patient, and not all patients follow them conscientiously.

If your own hospital lab staff has provided instructions, that's great! If not, ask them if these would be good to follow, to ensure that the sample is fresh and that the chemical levels for which they are testing are not artificially influenced by things in your diet. It is also very important that the urine be carefully refrigerated and preserved throughout the 24-hour urine collection period, and delivered fresh to the lab for immediate processing.

Preparation for Blood Testing

Do not take any medications without the testing doctor's knowledge and agreement. In particular, be sure to discuss theophylline, anti-hypertensives (blood pressure medicines), methyldopa, reserpine, guanethidine, L-dopa, or any diuretic.

Refrain from eating or drinking anything except water from 10 P.M. the evening prior to your blood test and that you not take any medications the morning of the test unless specifically okay'ed by the doctor administering the test. If you are instructed not to take your morning medications, please take them with you to the test so that you can take them right after the completion of the test.

In addition, it is recommended that you refrain from anything containing nicotine or caffeine at least three days prior to your test (i.e. cigarettes, cigars, coffee, tea, colas, etc.) If you have questions regarding your diet, please contact your physician.

The procedure usually takes about 45 minutes. It is important that you be quiet and calm for 30 minutes prior to the blood draw to ensure accurate results. Bring a book to read, or your walkman with some favorite music, something you will find relaxing.

Preparation for 24-hour Urine Testing.

For Vanillyl Mandelic Acid testing (VMA): Avoid chocolate, fruit (especially bananas) and any vanilla containing substance (cake, ice cream, pudding, etc.) for 48 hours prior to and during collection. Check with your doctor if you are taking Aldomet.

For Catacholamines, Metanephrines, Epinephrine, Norepinephrines: Avoid medications, chocolate, fruits (especially bananas) and any vanilla containing substance (cake, ice cream, pudding, etc.) for 48 hours prior to beginning collection and during collection.

Collection instructions: Do not begin collection on Friday or Saturday. This ensures that your sample will be delivered to the lab on a working day and can be processed promptly.

 

1. Start the collection in the morning. Empty the bladder and do not save this urine specimen

 

2. Write this date and time on the jug.

 

3. Save all the urine passed for the next 24 hours in the jug provided, include the final specimen passed exactly 24 hours after beginning the collection.

 

4. Keep the urine refrigerated at all times. (I know this seems gross. We kept ours in a paper bag in the fridge.)

 

5. Write this date and time on the jug when the collection is finished.

 

6. Bring the collection, along with the paper work, to the lab as soon as possible after collection. (Drop it off on the way to school or work. Labs are usually open early in the morning, or have a place where you can arrange to drop it off early).

 

* If there is a preservative added to the jug, be careful not to get it on the skin. If this happens, wash the area immediately with water.

Test instructions provided by Partners in Health, General Medicine Outpatient Service of the University of Michigan, Department of Internal Medicine.