CT Diagnosis of Thyroid Hemiagenesis Following Inconclusive Ultrasound in the Absence of Nuclear Medicine Imaging.

Thyroid hemiagenesis (THA) is a rare congenital condition in which one lobe of the thyroid fails to develop and is often discovered incidentally during imaging for unrelated conditions. We report the case of a 21-year-old woman who presented with generalized fatigue, cold intolerance, and irregular menstrual cycles. Physical examination and laboratory findings, including thyroid function tests, were within normal limits. An initial neck ultrasound was inconclusive due to technical limitations and the inadequate visualization of the thyroid anatomy. A subsequent computed tomography (CT) scan demonstrated the absence of the left thyroid lobe, confirming the diagnosis of thyroid hemiagenesis. Due to a lack of access to nuclear medicine imaging, radionuclide scanning was not performed. The patient was managed conservatively and advised regular follow-up. Thyroid hemiagenesis is often underdiagnosed and may be associated with other endocrine abnormalities, although many patients remain clinically stable. This case highlights the importance of adapting imaging strategies by utilizing available modalities when initial studies are inconclusive and gold standard investigations are not accessible. To our knowledge, this is the first documented case of thyroid hemiagenesis in Ethiopia and underscores the importance of awareness and flexibility in the diagnostic approach to rare congenital thyroid anomalies.