Gastrointestinal Tuberculosis

Tuberculosis (TB) is caused by Mycobacterium tuberculosis and historically is one of the oldest known human afflictions. According to the World Health Organization (2013), globally the annual incidence of TB was 8.6 million, and 1.3 million died in 2012. TB is the ninth leading cause of death worldwide, ranking above HIV/AIDS. In 2016 there were an estimated 1.3 million deaths from TB among HIV negative persons, and an additional 374,000 among HIV positive people. The countries with the highest incidence are India, Indonesia, China, and Philippines.

There are two forms of the mycobacterium complex, M. tuberculosis (the causative agent predominantly for TB in the human beings) and M. bovis (mostly found in cattle but a rare pathogen in the human). Pasteurization of cow's milk has resulted in the marked decline of M. bovis infection in most parts of the world. HIV infection may be complicated by tuberculosis, with a 20 times greater risk. In Africa, TB occurs in 20% to 26% of the HIV-infected population.

Although predominantly a pulmonary disease, TB also involves the central nervous system (tuberculous meningitis), lymphatic system, genitourinary system, bones and joints (Pott disease of the spine), and the gastrointestinal tract. The gastrointestinal tract, including the liver and pancreas, may be affected by tuberculosis. Extrapulmonary TB is noted in 15% of the cases worldwide. In the Unites States, one-fifth of the cases of TB are extra pulmonary, of which 5% are peritoneal.

Abdominal TB usually occurs in four forms: (1) tuberculous lymphadenopathy, (2) peritoneal, (3) gastrointestinal (GI), and (4) visceral (involving the genitourinary system, liver, spleen, and pancreas). Often a combination of two or more of the above occurs in a single patient. In tuberculous lymphadenopathy, the most frequently involved lymph nodes are mesenteric, omental, porta hepatis, celiac, and peripancreatic. Peritoneal TB may present in three forms: (1) the wet ascitic type is the most common, associated with large amounts of high-density free or loculated fluid with high protein content due to its inflammatory nature; (2) the fixed fibrotic type involving the omentum and mesentery shows matted bowel loops on imaging; (3) the dry plastic type has fibrous peritoneal reaction and adhesions.

The three modes of involvement of the gastrointestinal tract are (1) through ingestion of infected food material or sputum, (2) hematogenous spread from a tuberculous foci, and (3) direct spread to the peritoneum from an adjacent foci.

The ingested tuberculous bacteria in a susceptible individual invade the intestinal tract ( Fig. 113.1 ). The mucosal layer of the GI tract once infected with bacilli results in the formation of epithelioid tubercles. After 2 to 4 weeks, the tubercles undergo caseous necrosis and cause ulcerations. Invasion of the gut occurs primarily in lymphoid tissue. Therefore Peyer patches are susceptible. Terminal ileum, rich in lymphoid tissue, is most susceptible to intestinal TB. Morphologically, the intestinal tuberculosis may be either ulcerated or hypertrophic. In the ulcerated type, after invasion of the lymphoid follicles of Peyer patches, ulceration slowly develops. A necrotic base forms in the ulcer, which may perforate, or spread into the peritoneum. The less common hypertrophic type leads to extensive granuloma formation and fibrosis. In the colon, it can form a “napkin ring” lesion mimicking carcinoma.

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Gastrointestinal Tuberculosis: Pathways of Infection and Routes of Spread.

TB peritonitis may occur from dissemination or direct extension. Caseating granulomas are characteristic of the disease. TB involvement of the appendix has been reported.