title: Flip-flop phenomenon in radiohippuran renal imaging. A sign of obstructive nephropathy.
abstract: In the dynamic radionuclide brain study, decreased flow in one cerebral hemisphere during the arterial phase followed by relatively increased radioactivity as compared with the contralateral hemisphere has been termed the flip-flop phenomenon, and reflects the development of collateral circulation to the affected side. In I-131 Hippuran renal imaging, relatively decreased activity in one kidney frequently is observed during the initial phase of the study, and is followed by a gradual increase of radioactivity in the late images when compared with the contralateral kidney. To evaluate the significance of this renal flip-flop phenomenon, the studies from 23 patients with these findings were retrospectively compared with the clinical data and findings from other diagnostic studies (CT, ultrasound, intravenous pyelogram, autopsy). Partial obstruction of the renal collecting system was found in all 23 patients. The causes were various malignant tumors in nine patients (colonic carcinoma, three patients; transitional cell carcinoma, three patients; prostatic carcinoma, two patients; seminoma, one patient), ureteropelvic obstruction in three patients, papillary necrosis in one patient, and ureteral fibrosis in one patient. The flip-flop phenomenon reflects asymmetric renal tubular function with decrease (prolonged parenchymal transit time) in the affected kidney as a result of ipsilateral obstruction of the collecting system, while contralateral renal function remains normal or relatively normal. The presence of the flip-flop phenomenon in an I-131 Hippuran renal study suggests the existence of some degree of collecting system obstruction that has persisted long enough to result in renal parenchymal damage.
mesh_terms: D006801:Humans; D007465:Iodohippuric Acid; D007674:Kidney Diseases / Q000000981:diagnostic imaging*; D007680:Kidney Neoplasms / Q000000981:diagnostic imaging; D007681:Kidney Papillary Necrosis / Q000000981:diagnostic imaging; D004369:Pentetic Acid; D011866:Radioisotope Renography; D013667:Technetium; D016284:Technetium Tc 99m Pentetate; D014057:Tomography, X-Ray Computed; D014463:Ultrasonography; D014515:Ureteral Diseases / Q000000981:diagnostic imaging; D014517:Ureteral Obstruction / Q000000981:diagnostic imaging; D014567:Urography
chemical_list: D007465:Iodohippuric Acid; D013667:Technetium; D004369:Pentetic Acid; D016284:Technetium Tc 99m Pentetate