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A false positive I-131 MIBG due to dilated renal pelvis: a case report
Clinical Nuclear Medicine
|December 1, 1988
Abstract:
A case of false positive I-131 MIBG imaging for detection of pheochromocytoma is presented. There was an area of increased tracer uptake in the left renal region that showed steadily reducing activity over a period of three days. This raised the suspicion of a dilated renal pelvis, which was later confirmed by Tc-99m DTPA imaging. It is advisable in cases of ambiguous I-131 MIBG imaging to use Tc-99m DTPA rather than Tc-99m DMSA for localizing the kidneys and renal pelvis.
Insights
A case study highlights a false positive Iodine-131 MIBG scan for pheochromocytoma. Further imaging with Technetium-99m DTPA confirmed a dilated renal pelvis, not a tumor.
Area of Science:
- Nuclear medicine imaging
- Diagnostic radiology
- Oncology
Background:
- Iodine-131 MIBG (metaiodobenzylguanidine) scintigraphy is a standard imaging technique for diagnosing and staging neuroendocrine tumors, particularly pheochromocytomas.
- False positive results can lead to misdiagnosis and unnecessary treatment, emphasizing the need for accurate interpretation and complementary imaging modalities.
Observation:
- A patient presented with suspected pheochromocytoma based on Iodine-131 MIBG imaging showing increased tracer uptake in the left renal region.
- The activity in the identified region gradually decreased over three days, raising suspicion for a non-neoplastic cause.
Findings:
- The increased tracer uptake was determined to be a false positive finding for pheochromocytoma.
- Subsequent imaging using Technetium-99m DTPA (diethylene triamine pentaacetic acid) confirmed the presence of a dilated renal pelvis.
- Technetium-99m DMSA (dimercaptosuccinic acid) imaging was considered less suitable for this specific differential diagnosis.
Implications:
- This case underscores the importance of considering non-neoplastic mimics in I-131 MIBG imaging.
- Utilizing Tc-99m DTPA imaging is recommended for clarifying ambiguous renal findings in the context of I-131 MIBG scans.
- Accurate localization of renal structures is crucial for differentiating true pathology from physiological variants or anatomical abnormalities.