The Differential Diagnosis of Central Compartment Radioactive Iodine Uptake After Thyroidectomy: Anatomic and Surgical Considerations

Abstract

Foci of increased radioactive iodine (RAI) uptake in the thyroid bed following total thyroidectomy (TT) indicate residual thyroid tissue that may be benign or malignant. The use of postoperative RAI therapy in the form of remnant ablation, adjuvant therapy, or therapeutic intervention is often followed by a posttherapy scan. Our objective is to improve the clinician's understanding of the anatomic complexity of this region and to enhance the interpretation of postoperative scans. We conducted a comprehensive review of the literature evaluating RAI uptake in the central compartment following thyroid cancer treatment and literature related to anatomic nuances associated with this region. Thirty-eight articles were selected. Through extensive surgical experience and a literature review, we identified the 5 most important anatomic considerations for clinicians to understand in the interpretation of foci of increased RAI uptake in the thyroid bed on a diagnostic scan: 1) residual benign thyroid tissue at the level of the posterior thyroid ligament, 2) residual benign thyroid tissue at the superior portion of the pyramidal lobe and/or superior poles of the lateral thyroid lobes, 3) residual benign thyroid tissue that was left attached to a parathyroid gland in order to preserve its vascularity, 4) ectopic benign thyroid tissue, and 5) malignant thyroid tissue that has metastasized to central compartment nodes or invaded visceral structures. By correlating anatomic description, medical illustrations, surgical photos, and scans, we have attempted to clarify the reasons for foci of increased uptake following TT to improve the clinician's understanding of the anatomic complexity of this region.