Post-therapy iodine-131 localization in unsuspected large renal cyst: possible mechanisms.
Sensitive and specific, whole-body 131I scintigraphy remains an important technique for diagnosing metastases from differentiated papillary or follicular thyroid carcinoma. False-positive 131I localization is well recognized and can occur in a variety of conditions. We present a case of intense 131I localization in a previously unsuspected large renal cyst; the lesion was not visualized on routine preablation diagnostic 131I scintigraphy but was obvious on post-therapeutic whole-body imaging, underscoring the value of post-therapy imaging in detecting abnormalities not apparent on diagnostic studies. Radioiodine within the urinary bladder or, at times, the renal collecting system is expected, because 131I excretion is primarily by glomerular filtration. In the case presented here, 131I activity within the renal cyst supports the concept that iodide is subject to an active secretory process by the renal tubule.
Wen
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Department of Radiology, New England Medical Center and Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
Iuanow
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Oates
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Lee
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Perrone
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D002291:Carcinoma, Papillary / Q000000981:diagnostic imaging / Q000601:surgery; D005189:False Positive Reactions; D005919:Glomerular Filtration Rate; D006801:Humans; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics; D052177:Kidney Diseases, Cystic / Q000150:complications / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011859:Radiography; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D016284:Technetium Tc 99m Pentetate / Q000493:pharmacokinetics; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging* / Q000601:surgery; D013965:Thyroidectomy; D015899:Tomography, Emission-Computed, Single-Photon; D014463:Ultrasonography
D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D016284:Technetium Tc 99m Pentetate