000 Tuberculosis (TB) of the GI Tract – Cecum Ileum

Bovine Tuberculosis of the GI Tract

Etymology:
The term “bovine tuberculosis” (bTB) originates from the Latin tuberculum (small swelling) and refers to tuberculosis caused by Mycobacterium bovis, primarily affecting cattle but transmissible to humans.

AKA:

  • Bovine TB
  • Mycobacterium bovis infection
  • Tuberculous enteritis (when involving the bowel)

What is it?
Bovine tuberculosis is a zoonotic infection caused by Mycobacterium bovis, a member of the Mycobacterium tuberculosis complex (MTBC). It primarily affects cattle but can be transmitted to humans through the consumption of unpasteurized dairy products or close contact with infected animals.

Caused by:

  • Mycobacterium bovis infection
  • Ingestion of unpasteurized dairy products
  • Direct contact with infected cattle
  • Bovine tuberculosis (TB), caused by Mycobacterium bovis, primarily affects cattle but can also infect humans, leading to zoonotic TB. This bacterium can be transmitted to humans through the consumption of unpasteurized dairy products or, less commonly, via direct contact with infected animals.In humans, M. bovis infection can involve the gastrointestinal (GI) tract, with a predilection for the ileocecal region. This area is the most common site of GI TB involvement, with reported incidences ranging from 64% to 90%. The terminal ileum, ileocecal junction, and cecum are concurrently involved in the majority of cases.
  • The disease can be secondary to pulmonary infection, with the gastrointestinal lesions resulting from the ingestion of infected material or hematogenous spread from primary lung lesions. Infected cattle may exhibit symptoms such as weight loss, intermittent inappetence, and chronic diarrhea. Diagnosis is confirmed through histopathological examination, identification of acid-fast bacilli, and isolation of M. bovis.[1-2]
  • WFPI

    Isolated involvement of the terminal ileum occurs in up to one-third of small intestinal TB cases, while isolated cecal involvement is less common. Concurrent involvement of both the terminal ileum and cecum is more typical.

    ASM Journals

    Geographically, bovine TB remains endemic in various regions, particularly in parts of Africa, Latin America, and some Asian countries, where control measures may be less stringent. In developed countries, stringent control measures, including pasteurization of dairy products and testing of cattle herds, have significantly reduced the incidence of M. bovis infections in both cattle and humans.

    ASM Journals

    The presence of an “omental cake”—a radiological term describing thickening of the omentum due to infiltration by disease—can be associated with abdominal TB, including cases caused by M. bovis. However, this finding is nonspecific and can also be seen in other conditions such as peritoneal carcinomatosis. The occurrence of omental caking in abdominal TB varies and is not precisely quantified in the literature.

    In summary, bovine TB can lead to gastrointestinal involvement, most commonly affecting the ileocecal region, with isolated involvement of the terminal ileum occurring in a significant proportion of cases. The disease remains endemic in certain regions, emphasizing the importance of public health measures to control its spread.

  • GI TB and Pulmonary TB
    • exact percentage of patients with bovine tuberculosis enteritis who also have pulmonary tuberculosis is not available, it is reasonable to infer that a notable proportion of these patients may have extrapulmonary manifestations, including gastrointestinal involvement, with a smaller subset potentially having concurrent pulmonary tuberculosis. Further studies would be needed to provide precise figures.
    • Mycobacterium bovis, can lead to both pulmonary and extrapulmonary forms of tuberculosis in humans.

Resulting in:

  • Chronic granulomatous inflammation
  • Intestinal and peritoneal involvement
  • Lymphatic spread and systemic dissemination

Structural changes:

  • Thickening of the ileocecal region
  • Cecal and terminal ileal involvement
  • Pericolonic fat stranding
  • Omental thickening (omental cake)
  • Ascites and peritoneal enhancement

 

  • Pathophysiology:

Mycobacterium bovis enters through the gastrointestinal tract after ingestion of contaminated dairy products. The ileocecal region is commonly affected due to its unique lymphoid-rich tissue, which allows for bacterial proliferation and translymphatic spread. This process may lead to:

      • Ileocecal involvement with granulomatous inflammation
      • Peritoneal dissemination via translymphatic flow
      • Omental caking and ascites from peritoneal involvement
        1. Primary Involvement:
          • The ileocecal region is the most common primary site for gastrointestinal TB, including bovine TB.
          • This site is particularly vulnerable due to its relatively slow transit time, high concentration of lymphoid tissue (Peyer’s patches), and abundant lymphatic drainage.
        2. Translymphatic Spread:
          • The infection often spreads from the ileocecal region through the regional mesenteric lymphatics.
          • Lymphatic involvement can lead to:
            • Mesenteric lymphadenopathy
            • Omental caking due to lymphatic drainage of mycobacterial infection from the mesenteric lymph nodes.
        3. Transmural Disease:
          • The transmural involvement you’re describing, with pericolonic fat stranding, ascites, and mild peritoneal thickening, suggests:
            • Extension from the bowel wall due to severe inflammation and granuloma formation.
            • The case may represent advanced disease with serosal and peritoneal involvement secondary to either direct spread from the bowel wall or lymphatic seeding.
        4. Peritoneal Involvement and Ascites:
          • Tuberculous peritonitis can develop either from:
            • Rupture of a caseating lymph node into the peritoneal cavity.
            • Translymphatic spread with exudative peritoneal inflammation.
          • The ascites is typically exudative with high protein content and elevated SAAG (serum-ascites albumin gradient) compared to other causes.
        5. Omental Thickening (Omental Cake):
          • Omental involvement in TB can occur through:
            • Direct spread from involved bowel loops or mesenteric lymph nodes.
            • Translymphatic spread leading to granulomatous inflammation.
          • The “cake-like” appearance results from omental nodularity due to granulomas and fibrosis, which may mimic peritoneal carcinomatosis.

        Summary:

Pathology:

  • The lesions typically present as button-shaped ulcers in the mucosa overlying Peyer’s patches and adjacent mucosa, with marked granulomatous inflammation that can be transmural.[1]
  • Caseating granulomas
  • Necrotizing granulomas
  • Tuberculous lymphadenopathy
  • Multinucleated giant cells and epithelioid histiocytes

Diagnosis:

  • Clinical presentation with constitutional symptoms (fever, night sweats, weight loss)
  • History of exposure to unpasteurized dairy or endemic regions
  • Imaging findings of ileocecal thickening, omental caking, and peritoneal nodularity
  • Confirmatory tests:
    • Positive cultures for Mycobacterium bovis
    • PCR testing
    • Histopathology showing necrotizing granulomas

Clinical:

  • Abdominal pain
  • Weight loss
  • Fever
  • Night sweats
  • Ascites and abdominal distension

Radiology:

Radiological Imaging: Abdominal ultrasound and computed tomography (CT) scans are useful for identifying ascites, lymphadenopathy, bowel wall thickening, and other abnormalities.[3-5]
Abdominal Plain Film (KUB):

  • Findings: Nonspecific bowel distension, calcified lymph nodes
  • Associated Findings: Cecal thickening

CT:

  • Parts: Terminal ileum, cecum, mesentery, omentum, peritoneum
    • In humans, M. bovis infection can involve the gastrointestinal (GI) tract, with a predilection for the ileocecal region. This area is the most common site of GI TB involvement, with reported incidences ranging from 64% to 90%. The terminal ileum, ileocecal junction, and cecum are concurrently involved in the majority of cases.
      Isolated involvement of the terminal ileum occurs in up to one-third of small intestinal TB cases, while isolated cecal involvement is less common. Concurrent involvement of both the terminal ileum and cecum is more typical
  • Size: Thickened ileocecal region and pericolonic fat stranding
  • Shape: Concentric mural thickening and nodular omental caking
  • Position: Ileocecal region and peritoneal cavity
  • Character: Granulomatous inflammation with hypodense nodules
  • Time: Subacute to chronic presentation
  • Associated Findings: Ascites, mesenteric adenopathy, pericolonic fat stranding

MRI /PET CT/NM/US/Angio:

  • MRI: T2 hyperintensity with peritoneal enhancement
  • PET-CT: FDG avid granulomatous lesions
  • Nuclear Medicine: Positive sulfur colloid scan for splenic involvement in disseminated cases

Labs:

  • Positive Quantiferon-TB Gold or TST
  • Positive cultures for Mycobacterium bovis
  • Elevated inflammatory markers

Management:

  • First-line therapy: Isoniazid, Rifampin, Pyrazinamide, and Ethambutol (2 months) followed by Isoniazid and Rifampin (4 months)
  • Surgical intervention: Reserved for complications like obstruction or perforation

Recommendations:

  • Avoid unpasteurized dairy products in endemic regions
  • Vaccination of cattle (BCG vaccine in some countries)
  • Screening and eradication programs for infected livestock

Key Points and Pearls:

  • Bovine TB primarily involves the ileocecal region with associated peritoneal spread.
  • Translymphatic spread can result in omental caking and pericolonic fat stranding.
  • Imaging features overlap with other causes of omental thickening, including peritoneal carcinomatosis and pseudomyxoma peritonei.
  • Confirmatory diagnosis requires microbiologic or histologic evidence of Mycobacterium bovis.

Links and References