Which of the following organs is commonly involved in extrapulmonary tuberculosis?

- Extrapulmonary tuberculosis commonly involves the kidneys due to hematogenous dissemination of Mycobacterium tuberculosis from a primary pulmonary focus.
- The renal involvement can lead to tuberculous nephritis and ureteral strictures, causing symptoms such as hematuria and sterile pyuria.
- The kidneys are a frequent site because of their rich blood supply and the presence of the glomerulus, which filters circulating bacilli.
- In contrast, while other organs like the liver or spleen can be involved, renal tuberculosis is a classic and common manifestation of extrapulmonary disease.

Reference: Davidson’s Principles and Practice of Medicine, 23rd Edition, Chapter: Tuberculosis, Page 727.