Pheochromocytoma: A General Overview, Its Clinical Presentation, Diagnosis, Pharmacological Tests And Treatment
Profuse Sweating In Pheochromocytoma
Clinical Presentations And Diagnosis
Tumours arising from chromaffin tissue produce excess of catecholamines and give rise to hypertension and other effects. These may occur at several sites. Common among them are the adrenal medulla (90%), Zuckerkandl bodies adjacent to the abdominal aorta, paraganglionic cells of the sympathetic nervous system, urinary bladder, aortic or carotid bodies, and the mediastinum. It is seen that 0.1- 0.3% of hypertensive patients may have pheochromocytoma. The disease may be familial in 10% of cases and show an autosomal dominant inheritance. The familial form may occur in association with the syndrome of multiple endocrine adenomatosis such as MEA I (pituitary, parathyroid and pancreas) or MEA II (medullary carcinoma of the thyroid and parathyroid tumours or hyperplasia). Pheochromocytomas secrete large amounts of adrenaline and nor-adrenaline. Some tumours produce only one of these products. Of the pheochromocytomas, 90% are benign and 10% are malignant which may metastasize. The secondaries also produce the hormones.
The most prominent feature is hypertension which is paroxysmal in the initial stages and later becomes persistent. Hypertensive paroxysms are accompanied by headache, excessive sweating, tachycardia, fever, glycosuria and postural hypotention. Abdominal palpation, minor surgery and parturition may precipitate hypertensive attacks. The common hypotensive drugs like guanethidine, beta-adrenergic blockers and methyldopa lead to further elevation of blood pressure. Many develop malignant hypertension which may prove fatal. Hypertensive attacks accompanying micturition should suggest pheochromocytoma of urinary bladder.
Pheochromocytoma has to be clinically suspected in subjects developing paroxysmal hypertension associated with other manifestations of sympathetic overactivity. Diagnosis is established by demonstrating raised levels of vanilyl mandelic acid (VMA) which is the excretory product of catecholamines. Quantitative determinations are done in 24 hours collections of urine. Spot tests are also available for screening. Excretion of catecholamines in urine is also increased. Several drugs and articles of food produce false positive tests when urinary VMA or catecholamine determinations are done and, therefore, these have to be avoided. In extra-adrenal pheochromocytomas, noradrenaline constitutes more than 80% of the total secretion.
Hypertension In Pheochromocytoma
Elevation of blood pressure caused by histamine is suggestive. 0.025 mg histamine or 0.5 to 1.0 mg glucagon causes a rise in blood pressure in test subjects. An elevation of 50 mm Hg in systolic and 25 mm Hg in diastolic pressure is suggestive. There is a danger of precipitating hypertensive crisis by these tests.
Phentolamine (Regitine-Ciba) which blocks alpha-adrenergic system causes a prompt drop in blood pressure. The basal blood pressure is recorded and 5 mg of phentolamin is given intravenously. Blood pressure is recorded at 30 secs intervals for 3 minutes and 60 seconds intervals for 7 minutes. Fall in blood pressure above 35 mm Hg systolic and 25 mm Hg diastolic is suggestive. Adverse reactions include severe hypotensive crisis. The test is positive only during the hypertensive phase.
Localization of the tumour is achieved by CT scanning, ultrasonography, intravenous phyelography, retroperitoneal air insufflations and adrenal angiography. Selective sampling of adrenal venous blood for estimating catecholamines is the most useful confirmatory test. All these tests should be undertaken only in well equipped centers since there is the risk of sudden hypertensive crisis.
Treatment: Once the diagnosis is established, treatment is to remove the tumour surgically. Rapid fluctuations in blood pressure occur during premedication, anaesthesia, surgical manipulation and post-operative period. Pre-operatively, the blood pressure should be controlled by giving phenoxybensamine. Hypetensive episodes can be controlled by giving intravenous diazoxide or phentolamine. Adequacy of surgical treatment is assessed by monitoring urinary catecholamine levels.
© 2014 Funom Theophilus Makama