Understanding Pheochromocytoma: A Comprehensive Guide for Modern Family Physicians
Overview
Pheochromocytoma, a rare but serious condition, originates from chromaffin cells and can lead to significant health complications, particularly hypertension. This article provides a detailed overview of pheochromocytoma, its diagnosis, and treatment, offering valuable insights for modern family physicians.
What is Pheochromocytoma?
Pheochromocytoma is a tumor that arises from the adrenal medulla, sympathetic ganglia, or other chromaffin tissues. These tumors continuously or intermittently release large amounts of catecholamines, which can cause persistent or paroxysmal hypertension and multiple organ dysfunction and metabolic disturbances.
Key Characteristics
- Incidence: Pheochromocytoma predominantly affects individuals between 20 and 50 years of age, with no significant difference in male and female incidence rates.
- Location: Approximately 80-90% of pheochromocytomas are located in the adrenal glands, with 90% being unilateral. Bilateral cases or cases with one renal pheochromocytoma and another adrenal extramedullary tumor are rare.
- Nature: About 90% of pheochromocytomas are benign, with only about 10% being malignant.
Diagnosis
Pheochromocytoma is primarily characterized by cardiovascular symptoms, along with other systemic manifestations.
Symptoms
- Cardiovascular: The most common symptom is hypertension, which can be either persistent or paroxysmal. Symptoms during a paroxysm include severe headache, pallor, diaphoresis, tachycardia, precordial pain, arrhythmias, anxiety, fear, nausea, vomiting, blurred vision, and diplopia. Post-attack symptoms include erythema, facial flushing, fever, sialorrhea, and pupillary constriction. Hypotension or shock may also occur, or there may be alternating hypertension and hypotension.
- Metabolic: Disturbances in metabolic functions can include increased basal metabolism, disordered carbohydrate and lipid metabolism, and electrolyte disturbances.
- Other Systems: Symptoms may include constipation, intestinal necrosis, hemorrhage, perforation, bile stasis, abdominal mass, and asymptomatic gross hematuria.
Diagnostic Tests
- Blood and urine tests for catecholamines and their metabolites, such as vanillylmandelic acid (VMA), metanephrine (MN), and normetanephrine (NMN), which are often elevated.
- Insulin-induced glucose tolerance test, where an intravenous injection of glucagon is given to patients, and the plasma catecholamine level increases significantly.
- Ultrasound for adrenal and extramedullary (e.g., heart) tumor localization, with high positivity rate for adrenal tumors larger than 1 cm in diameter.
- CT scan, which can accurately locate over 90% of tumors, but may trigger hypertension episodes if not preceded by α-adrenergic antagonists.
- MRI, which can be used during pregnancy.
- Radioactive iodinated metaiodobenzylguanidine (MIBG) scintigraphy, particularly useful for metastatic, recurrent, or extramedullary tumors.
- Somatostatin analog labeled with a radioactive isotope, which helps in localization.
- Catheterization, which can roughly determine the location of the tumor.
Treatment
Control of Blood Pressure
- Alpha-blockers, such as phentolamine (phenylephrine) and prazosin, are commonly used to control blood pressure.
- In cases of hypertensive crisis, immediate intravenous slow injection of phentolamine 1-5 mg is recommended.
Surgical Treatment
- Surgical resection of the tumor is the preferred treatment for pheochromocytoma.
- Preoperative α-adrenergic blockade is crucial and usually lasts for at least 2 weeks.
Isotope Treatment
- For malignant pheochromocytoma, which is more difficult to treat, radioactive iodine MIBG therapy may be considered.
- Antidopaminergic drugs can be used for symptomatic treatment.
Prognosis
- Benign pheochromocytoma has a good prognosis, with a 5-year survival rate above 95% and a recurrence rate below 10%.
- The prognosis for malignant pheochromocytoma with metastasis is variable, with some patients surviving for more than 10 years, with a 5-year survival rate of about 45%.
Conclusion
For modern family physicians, recognizing the signs and symptoms of pheochromocytoma and understanding its diagnosis and treatment options are crucial. Early detection and management of this condition can significantly improve patient outcomes.