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 imaging 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 extrapulmonary 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 manifestation. 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.