A Diagnostic Puzzle: Unveiling Tuberculosis Peritonitis in an Immunocompromised Patient

Tuberculosis (TB) remains a leading cause of infectious morbidity and mortality worldwide. Extrapulmonary TB, particularly abdominal TB, is a diagnostic challenge due to its nonspecific presentation and often low sensitivity for conventional tests. Immunocompromised patients, such as those with human immunodeficiency virus (HIV), are at increased risk and may lack classic systemic symptoms, preventing timely diagnosis. A 61-year-old HIV-positive female on antiretroviral therapy and with an undetectable viral load presented with progressive abdominal distension, postprandial fullness, and altered bowel habits over two months. Physical examination revealed ascites and a right supraclavicular lymphadenopathy. Laboratory findings showed normocytic anemia, thrombocytosis, hypoalbuminemia, and elevated inflammatory markers. Computed tomography demonstrated large-volume ascites, bilateral pleural effusions, and signs of chronic liver disease. Ascitic fluid analysis revealed lymphocyte predominance with elevated adenosine deaminase (ADA) levels but was negative for Mycobacterium tuberculosis by cytology, culture, and polymerase chain reaction (PCR). A definitive diagnosis was established via laparoscopic peritoneal biopsy, which demonstrated granulomatous inflammation with PCR confirmation of M. tuberculosis. Quadruple anti-tuberculous therapy was started, and the patient was referred for specialized follow-up. The clinical course was favorable, resulting in complete resolution of the ascites. This case underscores the diagnostic difficulty of abdominal TB, especially in HIV-infected individuals who may lack typical symptoms. While ascitic fluid ADA measurement is a useful supportive test, peritoneal biopsy remains the gold standard in cases where fluid analysis is inconclusive. Early diagnosis and prompt initiation of anti-tuberculous treatment are essential to avoid complications and improve outcomes. Abdominal TB should be considered in the differential diagnosis of unexplained ascites, particularly in immunocompromised patients. Multimodal diagnostic evaluation, including invasive tissue sampling, is often required to establish the diagnosis and guide timely management.