Gastrointestinal tuberculosis (also known as tuberculous enteritis) is caused by infection with the organism Mycobacterium tuberculosis and may be seen with or without concomitant pulmonary tuberculosis.

Infection due to M. tuberculosis is a major worldwide health problem. In addition to pulmonary infection, this organism can cause infection of many extrapulmonary sites. The incidence of extrapulmonary tuberculosis in the United States has been increasing. Up to 20% of patients with tuberculosis in the United States have extrapulmonary disease, and gastrointestinal tuberculosis makes up a small percentage (< 5%) of cases of extrapulmonary tuberculosis.

Patients at increased risk for M. tuberculosis infection include patients with human immunodeficiency virus (HIV) disease or who are otherwise immunocompromised, although gastrointestinal tuberculosis remains an uncommon manifestation of tuberculosis in patients with AIDS. The infection should also be considered in patients with the usual risk factors for tuberculosis (including living in areas where tuberculosis is endemic or having a history of incarceration).

Pathophysiology
Infection of the gastrointestinal tract can result from swallowing infected sputum in patients with pulmonary tuberculosis or by ingesting contaminated milk or food. Infection may also be the result of hematogenous spread or by contiguous spread from adjacent organs. 

Presentation
Any part of the gastrointestinal tract may be involved, but most commonly the infection involves the terminal ileum, cecum, or ascending colon. Symptoms of infection are frequently nonspecific and are usually present for months. In one series, abdominal pain, fever, and anorexia were very common. There may be associated night sweats, weight loss, diarrhea, or constipation. Intestinal obstruction may be seen. Intestinal lesions may be ulcerative and less commonly hypertrophic on endoscopy. Mass lesions may be seen on abdominal imaging. In some cases, the infection can present with oral ulcers or it may mimic Crohn disease.

In addition to the intestine, tuberculosis may also affect the peritoneum or the mesenteric lymph nodes. Tuberculous peritonitis may present simultaneously with tuberculous infection of the intestine (due to contiguous spread or bowel perforation), but it may also present independently (likely due to hematogenous seeding of the peritoneum). The symptoms of tuberculous peritonitis are usually subtle and can be present for weeks or months before diagnosis. Some patients will not have any constitutional symptoms. The two classic syndromes of tuberculous peritonitis are the wet-ascitic form and the dry-plastic form. However, in clinical practice, these forms are seen to overlap. Ascites, abdominal discomfort, and fever are common. The dry-plastic form is rare. These patients present with the classic "doughy abdomen" and very little ascites. They have many adhesions seen on laparoscopy.

Additionally, M. tuberculosis can infect the pancreas (with many different imaging patterns described) or the hepatobiliary system (rarely presenting as tuberculous cholangitis).