MULTISYSTEM RADIOLOGY 2023 Extrapulmonary Tuberculosis: Pathophysiology and Imaging Findings Extrapulmonary tuberculosis (TB) represents approximately 15% of all TB infections. It is difficult to diagnose on the basis of imag- ing characteristics and clinical symptoms, and biopsy is required in many cases. Radiologists must be aware of the imaging findings of extrapulmonary TB to identify the condition in high-risk patients, even in the absence of active pulmonary infection. In extrapulmo- nary TB, the lymphatic system is most frequently affected. The presence of necrotic lymph nodes and other organ-specific imaging features increases the diagnostic probability of extrapulmonary TB. Disseminated infection and central nervous system involvement are the most frequent manifestations in immunosuppressed patients. Renal disease can occur in immunocompetent patients with very long latency periods between the primary pulmonary infection and genitourinary involvement. In several cases, gastrointestinal, solid-organ, and peritoneal TB show nonspecific imaging findings. Tuberculous spondylitis is the most frequent musculoskeletal mani- festation. It is usually diagnosed late and affects multiple vertebral segments with extensive paraspinal abscess. Articular disease is the second most frequent musculoskeletal manifestation, and synovitis is its predominant imaging finding. © RSNA, 2019฀•฀radiographics.rsna.org SaraYukie Rodriguez-Takeuchi, MD Martin Eduardo Renjifo, MD Francisco José Medina, MD Abbreviations: CSF = cerebrospinal fluid, HIV = human immunodeficiency virus, TB = tuberculosis RadioGraphics 2019; 39:2023–2037 https://doi.org/10.1148/rg.2019190109 Content Codes: From the Department of Radiology, Fundación Valle del Lili–Universidad Icesi, Carrera 98 #18-49, Cali, Colombia. Presented as an educa- tion exhibit at the 2018 RSNA Annual Meeting. Received April 14, 2019; revision requested June 26 and received July 20; accepted July 31. For this journal-based SA-CME activity, the authors, editor, and reviewers have disclosed no relevant relationships. Address correspondence to S.Y.R.T. (e-mail: syukierodriguez@gmail.com, sara.rodriguez@fvl.org.co). © RSNA, 2019 After completing this journal-based SA-CME activity, participants will be able to: ■ Identify imaging features that are sug- gestive of extrapulmonary TB in high- risk patients. ■ Describe the pathophysiology of extra- pulmonary TB. ■ Compare the imaging features of extrapulmonary TB to those of other in- fectious and noninfectious diseases. See rsna.org/learning-center-rg. SA-CME LEARNING OBJECTIVES Introduction Tuberculosis (TB) is an infectious disease caused by the bacillus Mycobacterium tuberculosis. According to the World Health Organiza- tion, TB is one of the top 10 causes of mortality worldwide and is the leading cause of death from a single infectious agent. It is estimated that 10 million people developed TB in 2017 (1). TB typically manifests with pulmonary infection. However, it can affect other areas of the body. Extrapulmonary TB occurred in 14% of TB cases in 2017 (1). It affects the lymph nodes most frequently, followed by pleural infection. The presence of necrotic lymph nodes and other organ-specific imaging features increases the diagnostic probability of extrapulmonary disease (2). Extrapulmonary TB can occur in immunocompetent and immu- nocompromised patients. Patients with human immunodeficiency virus (HIV) and TB have a higher incidence of extrapulmonary manifestations, a higher susceptibility to latent disease reactivation, and a higher probability of developing disseminated disease than other patients. Moreover, lymphatic, miliary, and central nervous system (CNS) TB are more prevalent in this population (3). Extrapulmonary TB can be challenging to diagnose, and biopsy is required in many cases. We describe the pathophysiology of extrapulmonary TB and its imaging findings, including how to dif- ferentiate extrapulmonary TB from other infectious and noninfec- tious diseases (4). This copy is for personal use only. To order printed copies, contact reprints@rsna.org