A 52-year-old man with a 10-year history of hypertension presents with episodic severe headaches, profuse sweating, and palpitations lasting 20–30 minutes. Blood pressure during an episode is 210/120 mmHg; baseline is 160/95 mmHg. Plasma metanephrines are elevated. Which investigation is most appropriate to confirm the diagnosis and localize the lesion?

Question

Accepted Answer

B. CT abdomen with contrast. ## Diagnosis: Pheochromocytoma

The clinical presentation—episodic hypertension with classic triad of headache, sweating, and palpitations—combined with elevated plasma metanephrines strongly suggests pheochromocytoma. Once biochemical diagnosis is confirmed, **anatomical localization** is the next critical step.

## Investigation of Choice: CT Abdomen with Contrast

**Key Point:** After biochemical confirmation (plasma or 24-hour urine metanephrines), **CT abdomen with IV contrast** is the first-line imaging modality to localize the tumor.
- Sensitivity ~95% for adrenal pheochromocytomas
- Excellent spatial resolution for masses >1 cm
- Can detect extra-adrenal tumors (paragangliomas) along the sympathetic chain
- Rapid and widely available

## Why CT Over Other Imaging?

**High-Yield:** MRI is equally sensitive but slower and less accessible in acute settings. MIBG scintigraphy is reserved for metastatic disease or when CT/MRI is inconclusive. PET-CT is not first-line.

## Clinical Pearl

Contrast-enhanced CT can differentiate pheochromocytoma from benign adrenal adenoma by assessing washout characteristics (pheochromocytomas retain contrast longer). Always obtain imaging **before** any invasive procedure (biopsy, angiography) to avoid catecholamine release.

## Biochemical Confirmation Sequence

```mermaid
flowchart TD
  A[Clinical suspicion: episodic HTN + symptoms]:::outcome --> B[Plasma metanephrines or 24h urine metanephrines]:::action
  B --> C{Elevated?}:::decision
  C -->|Yes| D[Biochemical diagnosis confirmed]:::outcome
  D --> E[CT abdomen with contrast]:::action
  E --> F[Tumor localized]:::outcome
  C -->|No| G[Pheochromocytoma unlikely]:::outcome
```

Answer

A. Renal artery duplex ultrasound

Answer

C. 24-hour urinary metanephrines

Answer

D. Plasma free catecholamines

Explanation

Diagnosis: Pheochromocytoma

Investigation of Choice: CT Abdomen with Contrast

Why CT Over Other Imaging?

Clinical Pearl

Biochemical Confirmation Sequence

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