GI TB is a major health problem in many underdeveloped countries. A recent significant increase has occurred in developed countries, especially in association with HIV infection. Autopsies of patients with pulmonary TB before the era of effective treatment demonstrated intestinal involvement in 55-90% of fatal cases. The previously noted frequent association between pulmonary TB and intestinal TB no longer prevails, and only a minority of patients (< 50%) with abdominal TB now have abnormal chest radiographic findings. However, approximately 20-25% of patients with GI TB have pulmonary TB. Any part of the GI system may be infected, although the ileum and colon are common sites.
Clinical features of intestinal TB include abdominal pain, weight loss, anemia, and fever with night sweats. Patients may present with symptoms of obstruction, right iliac fossa pain, or a palpable mass in the right iliac fossa. Hemorrhage and perforation are recognized complications of intestinal TB, although free perforation is less frequent than in Crohn disease.
Malabsorption may be caused by obstruction that leads to bacterial overgrowth, a variant of stagnant loop syndrome. Involvement of the mesenteric lymphatic system, known as tabes mesenterica, may retard chylomicron removal because of lymphatic obstruction and result in malabsorption.
The ileum is more commonly involved than the jejunum. Ileocecal involvement is seen in 80-90% of patients with GI TB. This feature is attributed to the abundance of lymphoid tissue (Peyer patches) in the distal and terminal ileum.
Proximal small intestinal disease is seen more commonly with M avium-intracellulare (MAI) complex infection, predominantly infection involving the jejunum. Intestinal obstruction may be partial or complete with TB. Segmental involvement usually is in a stenotic form.
CT scans show mesenteric lymphadenopathy with a hypoattenuating center suggestive of necrosis. Distinguishing M tuberculosis from MAI complex infections in patients with AIDS may be possible. Diffuse jejunal wall thickening and enlarged soft-tissueattenuating lymph nodes with hepatosplenomegaly suggest disseminated MAI complex infection, whereas focal abdominal lesions with low-attenuating lymph nodes suggest disseminated M tuberculosis. MAI complex infection is also called pseudo-Whipple disease because of the diffuse mucosal fold thickening in the jejunum and histiocytic aggregates infected with MAI that stain positive with periodic acidSchiff testing.
Abdominal lymphadenopathy in intestinal TB may be demonstrated with US and CT. The distribution of lymphadenopathy is sometimes difficult to differentiate from lymphoma. Contrast-enhanced CT may be useful in differentiating lymphomas from TB. Mesenteric lymph nodes are involved more often in disseminated TB (80%) and in nondisseminated TB (52%) than in patients with untreated Hodgkin disease (6%).
The most common site of GI TB is the ileocecal region, if the area can be reached with a flexible endoscope. A rapid diagnosis can be achieved if smear or culture results are positive or if caseating granulomas are seen in biopsy samples. In countries where GI TB is endemic, a therapeutic trial of antituberculosis treatment may be justified if the clinical picture is compatible with TB.