S2060 Gastrointestinal Tuberculosis: The Great Masquerader

INTRODUCTION: Gastrointestinal tuberculosis (GI-TB) is the sixth most common presentation of extra-pulmonary TB. Diagnosis is challenging due to its mimicry of other conditions like neoplasia, inflammatory bowel disease, and other infections. Though rare in Singapore and other developed countries, this case report highlights GI-TB as an important differential diagnosis for gastrointestinal malignancy. CASE DESCRIPTION/METHODS: A 32-year-old female presented with right-sided abdominal pain and significant weight loss. Laboratory evaluation showed iron deficiency anemia. Computed Tomography (CT) revealed ileocolonic lymphadenopathy and a right iliac fossa mass with thickening of the terminal ileum (TI), cecum, and ascending colon (Figure A). Colonoscopy showed a circumferential and ulcerated ascending colon mass with severe stenosis precluding passage of a pediatric colonoscope across the stricture (Figure B). Histology from endoscopic biopsy of the mass demonstrated ulceration, inflammatory granulation tissue and focal granulomatous histiocytic aggregates without caseous necrosis. There was no histopathologic evidence of malignancy. Acid-fast bacilli (AFB) smear and polymerase chain reaction (PCR) for TB and cytomegalovirus were negative. However, serum TB T-spot was positive. The patient's clinical course was soon complicated by symptomatic ascites. Ascitic fluid analysis for TB PCR, AFB smear and culture, and cytology was negative. Serum-ascites albumin gradient was 11 g/L. As the diagnosis remained inconclusive, repeat colonoscopy with endoscopic biopsy of the mass lesion was performed. TB PCR and AFB smear were again negative but TB culture eventually grew Mycobacterium tuberculosis. The patient was treated for GI-TB for six months with symptom resolution. Follow-up colonoscopy was successfully completed to TI and showed resolution of the previous mass and associated stricture (Figure C). DISCUSSION: This case illustrates how GI-TB may present with non-specific clinical symptoms similar to other conditions including GI malignancies, inflammatory bowel disease and other gut infections. Its varied clinical manifestations may make diagnosis difficult and elusive. A high index of clinical suspicion for GI-TB should therefore be maintained when evaluating atypical cases. The approach to such cases requires a combined clinical, radiologic, endoscopic and histopathologic assessment for prompt diagnosis and management of these patients.Figure A.: Initial Computed Tomography (CT) depicting mesenteric lymphadenopathy and marked thickening of the cecum, proximal ascending colon and terminal ileum associated with extensive fat stranding.Figure B.: Initial colonoscopy showing a circumferential and ulcerated ascending colon mass with significant stenosis (tattooed area), preventing passage of a paediatric colonoscope.Figure C.: Follow-up complete colonoscopy to cecum and terminal ileum showing resolution of ascending colon mass and associated stricture at previously tattooed site.