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Phaeochromocytoma assessment

Adrenal Mibg Scan 140X112

 

Metanephrines guidance

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A phaeochromocytoma (PCC) is a neuroendocrine tumour of the adrenal medulla (originating in the chromaffin cells,) or extra-adrenal chromaffin tissue that failed to involute after birth which typically secretes excessive amounts of catecholamines - usually noradrenaline (norepinephrine) and adrenaline (epinephrine) to a lesser extent.

Indications

Urinary metanephrines assay is the first-line screening test for phaeochromocytoma

Preparation

  • Patients may eat and drink normally prior to test. Written instructions must be given to the patient prior to performing this test to ensure that both 24 hour collections are performed accurately.
  • Two special 24 hour collection bottles containing acid preservative should be provided to the patient in advance. Caffeine and cigarettes should be avoided for four hours and all over-the-counter medicines should be avoided for 48 hours before the test, as paracetamol can cross-react with assays and cough medicines may contain sympathomimetics (click here for further information.)

Procedure

  • Patients are informed to choose two convenient days to perform their urinary collections. The two days need not necessarily be consecutive.
  • Patients need to be advised that the collection bottles contain a preservative and so should not pass urine directly into them.
  • Patients are advised to empty their bladder into the toilet normally on waking on the morning that they start a collection and note the time. From that time onwards, all urine passed that day should be collected into a plain collection bottle. All urine passed during that night should also be collected.
  • The patient should set an alarm if necessary to wake them by the same time the following morning. That morning, the patient should empty their bladder and collect this as the final sample into the same bottle as from the previous day. This means that they start and finish the collection with an empty bladder at the same time of day.
  • The test should then be repeated on a second day and both collections brought in together for analysis.

Expected results

Metanephrine (MN) <2000 nmol/24 hrs
Normetanephrine (NMN) <4400 nmol/24 hrs
3-methoxytyramine (3-MT) <2500 nmol/24 hrs

References

This investigation is taken from "Endobible: Practical guidance on endocrine diagnosis and management," K.Meeran et al. (http://www.endobible.com/investigation/urinary-metanephrines/)

Last updated: 25 February 2016