Abdominal TB can be subdivided into clinically distinct or overlapping presentations, comprising gastrointestinal disease (luminal), peritoneal, visceral, and abdominal lymph node disease. Gastrointestinal and peritoneal forms of TB disease occur most frequently and are the focus of this section. Isolated visceral and abdominal lymph node disease are uncommon forms of abdominal TB.131,132
3.3.1. Gastrointestinal TB
TB may affect any part of the gastrointestinal tract. Ileocecal and jejunoileal involvement are most common (up to 75% of cases), followed by colorectal disease (majority on right side).131–134 Gastrointestinal TB, particularly ileocecal disease, may present with clinical and radiographic features that are indistinguishable from Crohn’s disease, such as chronic abdominal pain, constitutional symptoms and a right lower quadrant mass.135,136 Mesenteric lymph node enlargement is more commonly found on diagnostic imaging in patients with gastrointestinal TB than in patients with inflammatory bowel disease.137–140
Diagnostic testing for gastrointestinal TB includes stool studies for M. tuberculosis and, where available, endoscopy for biopsies with multiple dedicated samples sent for both culture/NAAT in saline and histopathology to maximize diagnostic yield. Collectively, these tests may support or confirm diagnosis of TB in up to 70% of cases (see Table 1).133,141–143
If endoscopy is nondiagnostic, laparoscopy/laparotomy can be considered for definitive diagnosis. An empiric trial of anti-TB therapy may be required in some cases. However, in addition to the usual concerns regarding empiric therapy, partial short-term clinical response of Crohn’s disease to anti-TB therapy is well described and may confound diagnosis.144 Such delays in Crohn’s disease treatment have been shown to worsen long-term outcomes (increased rates of stricture and future surgery).135,144,145 When empiric TB therapy is pursued, end-of-treatment endoscopy may be helpful in differentiating TB disease as significant or complete mucosal healing is reported in more than 75% of cases.133,143
3.3.2. Peritoneal TB
TB involving the peritoneum presents most commonly (in more than 60% of cases) with abdominal swelling secondary to ascites, often concurrent with abdominal pain, fevers and/or weight loss.38,40 Individuals with chronic liver disease (particularly alcoholic liver disease), chronic renal disease and HIV are at increased risk.7,18,146
Radiologic assessment can be helpful but is not diagnostic in peritoneal TB.137,140,147 Diagnosis of peritoneal TB typically starts with percutaneous sampling of ascites for fluid analysis, microscopy and culture. Assessment of ascitic fluid classically demonstrates a proteinaceous exudative pattern (protein greater than 30 grams per L) with a predominance of lymphocytes (greater than 70%) and a low (less than 11 grams per L) serum ascites albumin gradient (SAAG). However, when TB peritonitis complicates chronic peritoneal dialysis or decompensated cirrhosis, it may not have this typical ascites profile. Ascitic fluid is rarely AFB-smear positive but may culture M. Tuberculosis in up to 80% of cases. Larger volume (greater than 1 liter) and concentration of samples are reported to increase culture yield.38,148 If ascitic fluid sampling is nondiagnostic, peritoneal biopsy (diagnostic image-guided or laparoscopic) for AFB smear, culture, NAAT and histopathology should be considered, as diagnostic yield for peritoneal tissues is significantly higher than ascitic fluid alone (See Table 1).38,41,149 ADA testing is not used in Canada (see Chapter 3: Diagnosis of Tuberculosis Disease and Drug-resistant Tuberculosis).
It is important to recognize that peritoneal and other forms of TB can cause an elevation in serum tumor marker CA 125 levels. Given shared radiographic findings with peritoneal carcinomatosis of metastatic ovarian cancer, there are numerous case reports of misdiagnosis of malignancy, underscoring the importance of pursuing tissue and/or culture diagnosis of peritoneal TB.39,150
3.3.3. Abdominal TB treatment
Three clinical trials evaluating treatment of abdominal TB consistently found that 6 months of standard anti-TB treatment is adequate in individuals with drug-susceptible abdominal TB and extension of treatment does not significantly improve clinical cure or relapse risk. The available evidence is limited to HIV-negative individuals and strongest for gastrointestinal forms of abdominal TB.151
Surgery should generally be reserved for abdominal TB cases with serious complications, such as perforation, bleeding or obstruction.152
We conditionally recommend six months of standard anti-TB therapy for all forms of drug-susceptible abdominal TB (poor evidence).
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