title: False-positive radioiodine uptake in the abdomen and the pelvis: radioiodine retention in the kidneys and review of the literature.
abstract: Because the kidneys are usually not visualized on radioiodine whole-body scans, the renal uptake can be mistaken for a thyroid cancer metastasis. The authors report the prevalence and characteristics of radioiodine retention in the kidneys and review the reported causes of false-positive radioiodine uptake in the abdomen and pelvic areas. Radioiodine uptake in the renal bed was noted on 9 of 400 (2.2%) I-123 diagnostic whole-body scans performed over a 7-month period in our center. The uptake was noted more clearly on posterior views, cleared on delayed images after further hydration, and was not consistently present on follow-up scans. It was unilateral and mimicked a renal or adrenal metastasis in 44% of the scans. In three cases, the uptake was associated with a dilated calyx, an extrarenal pelvis, or a voluminous pelvis. False-positive radioiodine uptake in the abdomen and pelvis has been previously reported in association with 14 different conditions. However, renal retention may represent the most common cause of false-positive radioiodine uptake in the abdomen pelvis. Delayed imaging after additional hydration is usually sufficient to clarify its origin.
authors.affiliation: Department of Radiology, King Faisal Specialist Hospital, Riyadh, Saudi Arabia.
authors.forename: S M
authors.initials: SM
authors.lastname: Bakheet
authors.forename: M M
authors.initials: MM
authors.lastname: Hammami
authors.forename: J
authors.initials: J
authors.lastname: Powe
mesh_terms: D000005:Abdomen / Q000000981:diagnostic imaging*; D000310:Adrenal Gland Neoplasms / Q000000981:diagnostic imaging / Q000556:secondary; D000328:Adult; D000368:Aged; D003937:Diagnosis, Differential; D004108:Dilatation, Pathologic / Q000000981:diagnostic imaging; D004326:Drinking; D005189:False Positive Reactions; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007089:Image Enhancement; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics; D007668:Kidney / Q000000981:diagnostic imaging* / Q000378:metabolism; D007670:Kidney Calices / Q000000981:diagnostic imaging / Q000473:pathology; D007674:Kidney Diseases / Q000000981:diagnostic imaging; D007680:Kidney Neoplasms / Q000000981:diagnostic imaging / Q000556:secondary; D007682:Kidney Pelvis / Q000002:abnormalities / Q000000981:diagnostic imaging / Q000473:pathology; D008297:Male; D008875:Middle Aged; D010388:Pelvis / Q000000981:diagnostic imaging*; D015995:Prevalence; D011446:Prospective Studies; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D013964:Thyroid Neoplasms / Q000000981:diagnostic imaging
chemical_list: D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals