Phaeochromocytoma without hypertension

Case history

A 34 year old woman presented with a 10 week history of paroxysmal attacks of headache associated with vomiting, sweating,and palpitations. Her blood pressure always remained normal during these episodes. A 24 hour urine collection showed a mildly elevated level of adrenaline at 180 nmol/24hr (normal
< 140nmol/24hr) with normal levels of noradrenaline and dopamine. Abdominal computed tomography (CT) showed the following abnormality (see figure).

Abdominal computed tomography scan showing a cystic lesion arising from the right adrenal gland impinging on the liver capsule and the inferior vena cava

Questions

1. What abnormality is seen on the scan?
2. What is the likely diagnosis?

Answers

1. A cystic adrenal tumour.
2. Adrenal phaeochromocytoma.

Discussion

Phaeochromocytoma is an uncommon tumour with an incidence estimated at 0.8 per 100 000 person years. It is associated with a variety of symptoms including headache, palpitations, sweating, and anxiety. Hypertension, which may be sustained or paroxysmal, is believed to be the most consistent clinical sign. However, there are case reports of normotensive patients with raised levels of epinephrine and norepinephrine.¹ A recent Italian multicentre study of 284 cases of phaeochromocytoma found that 21% of the patients had normal blood pressure both in the supine and upright positions.²

Why patients with phaeochromocytoma who have raised catecholamines can have normal blood pressure is unclear. In small tumours the catecholamine store is replaced at a more rapid rate and large amounts of catecholamines are released into the host. On the other hand, in large tumours a considerable portion of catecholamine synthesised is metabolised directly in the tumour, causing less effect on the blood pressure.³ It is known that in addition to epinephrine and norepinephrine, other vasoactive substances are secreted by the tumour. Several vasodilatory peptides, such as calcitonin gene related peptide and vasoactive intestinal peptide, may be responsible for normal or low blood pressure in these patients, ³

Investigations

To screen for phaeochromocytoma, 24 hour urinary excretory rates of catecholamines and their metabolites--for example, norepinephrine, epinephrine, dopamine, metanephrine, normetanephrine--are useful. These measurements provide close to 100% specificity and sensitivity in diagnosing the condition. CT, magnetic resonance imaging (MRI), and scanning with iodine-131-meta-iodobenzylguanidine (MIBG) are commonly used in localising the tumour. The specificity of a MIBG scan approaches 100% (making it very useful for extra-adrenal lesions), but its sensitivity is only 80%.⁴ CT and MRI scans have a sensitivity of 98% to 100% but a specificity of no greater than 70%.⁴ The combination of CT and MIBG scanning is the most practical and cost effective initial method of localisation.

Treatment

The immediate aim in the treatment of phaeochromocytoma is to control the adverse effects of circulating catecholamines: high blood pressure, arrhythmias, and anxiety. Phenoxybenzamine, an irreversible long acting *-adrenergic blocker, is the mainstay of medical treatment to control blood pressure.

This drug should be started in small doses (10 mg two or three times a day) and increased as needed to normalise blood pressure and to eliminate related symptoms. Other more selective *-blockers, such as prazosin, terazosin, and doxazosin can also be considered. Beta blockers are then administered for two reasons: firstly, to limit symptoms and signs due to increased circulating catecholamines and secondly to block excessive cardiac sympathetic drive secondary to suppression of the presynaptic *-2 regulating mechanism by drugs, such as phenoxybenzamine. ß adrenergic blockade should be administered after the *-blockade has become effective, otherwise more severe hypertension may result from unopposed *-adrenegic stimulation.

Complete resection of the tumour provides a permanent cure. The operation remains an anaesthetic challenge, as rapid fluctuations in blood pressure may occur due to the catecholamines released by manipulation of the gland. Phentolamine, sodium nitroprusside, magnesium sulphate, isoflurane, and calcium channel blockers are some of the drugs used to limit these effects during surgery.⁵

Recently laparoscopic excision of the tumour has become increasingly popular. Open excision is still preferred in patients with large tumours ( > 8cm) and where malignancy is suspected.

Arul Ganeshan, surgical senior house officer,
John Baxter honorary consultant surgeon, Morriston Hospital, Swansea SA6 6NL
Email: email


studentBMJ 2002;10:89-130 April ISSN 0966-6494

1. Smircic L, Suskovic T, Ferencic Z. Phaeochromocytoma without hypertension. J Intern Med 1994;235:373-4.
2. Mannelli M, Ianni L, Cilotti A, Conti A. Phaeochromocytoma in Italy: a multicentre retrospective study. Eur J Endocrinol 1999;141:619-24.
3. Samaan NA, Hickey RC, Shutts PE. Diagnosis, location and management of phaeochromocytoma. Pitfalls and follow up in 41 patients. Cancer 1988;62:2451-60.
4. Foo M, Burton BJ, Ahmed R. Phaeochromocytoma. Br J Hosp Med 1995;54:318-21.
5. Pry-Roberts C. Phaeochromocytoma: recent progress in its management. Br J Anaesth 2000;85:44-57