Does pheochromocytoma always show up on computed tomography (CT) scans of the abdomen and pelvis?

Pheochromocytoma Detection on CT Abdomen and Pelvis

No, pheochromocytoma does not always show up on CT abdomen and pelvis scans, as these tumors can have variable imaging appearances and some may be missed on conventional CT imaging alone.

Diagnostic Challenges with Pheochromocytoma on CT

• CT scanning is a first-line imaging modality for localizing pheochromocytoma after biochemical confirmation, but it has limitations in detecting all cases 1, 2
• Pheochromocytomas typically appear as heterogeneously enhancing masses with irregular margins on CT, but their appearance can vary significantly 1, 3
• Up to 70% of pheochromocytomas are discovered incidentally on imaging, suggesting that some may be present without typical clinical manifestations 3
• Small pheochromocytomas or those in atypical locations may be missed on conventional CT imaging 1

Factors Affecting CT Detection

• Size: Smaller pheochromocytomas may be difficult to visualize on standard CT protocols 3
• Location: Extra-adrenal paragangliomas can occur in various atypical locations that might not be included in standard abdomen/pelvis CT imaging fields 1
• Timing of contrast: Optimal visualization may depend on specific contrast protocols and timing of image acquisition 1
• Technical factors: Slice thickness, patient factors, and scan quality can affect detection rates 1

Complementary Imaging Approaches

• When clinical suspicion for pheochromocytoma exists but CT findings are negative or equivocal, additional imaging modalities should be considered 2:
  • MRI offers superior soft tissue contrast and can detect some lesions missed on CT 1
  • Functional imaging with 123I-MIBG scintigraphy, 18F-FDOPA PET, or 18F-FDG PET provides higher sensitivity for detecting small or atypically located tumors 1, 2
  • Combined anatomical and functional imaging (SPECT/CT or PET/CT) significantly improves diagnostic accuracy 1

Diagnostic Algorithm for Suspected Pheochromocytoma

1. Initial biochemical confirmation with plasma free metanephrines or 24-hour urinary fractionated metanephrines 1, 2
2. First-line anatomical imaging with CT or MRI of abdomen and pelvis 1, 2
3. If initial imaging is negative but biochemical evidence is positive:
   • Extend imaging to include chest and neck 1, 4
   • Consider functional imaging with 123I-MIBG, FDOPA-PET, or FDG-PET 1, 2
4. For high-risk patients (genetic syndromes, family history), consider more sensitive functional imaging even with negative CT 1, 2

Important Clinical Considerations

• Biopsy of suspected pheochromocytoma is contraindicated due to risk of hypertensive crisis 1, 2
• Biochemical testing should always precede imaging for suspected pheochromocytoma 1
• Even with negative imaging, if biochemical evidence strongly suggests pheochromocytoma, further investigation is warranted 2, 4
• Approximately 25% of pheochromocytomas have genetic associations, which may influence imaging characteristics and detection rates 4, 5

Common Pitfalls in Diagnosis

• Relying solely on CT imaging without biochemical confirmation 1, 2
• Failing to consider extra-adrenal locations when adrenal imaging is negative 1
• Not recognizing that some pheochromocytomas may have atypical imaging appearances 3
• Overlooking the need for specialized imaging protocols optimized for adrenal evaluation 1
• Attempting biopsy of an undiagnosed adrenal mass without ruling out pheochromocytoma 1, 2