Revealing the Hidden Pathogen: The Role of Positron Emission Tomography in Diagnosing Amoebic Liver Abscess in an Immunocompetent Patient

A 26-year-old male reported with high-grade fever accompanied by chills and rigours persisting for four days, followed by vomiting and dull, aching pain in the right hypochondrium. Laboratory investigations revealed leucocytosis with raised procalcitonin levels. An abdominal ultrasound (USG) showed no liver parenchymal abnormalities. As the patient’s symptoms persisted despite antibiotic therapy, a comprehensive pyrexia of unknown origin (PUO) workup was undertaken. Serological tests for Toxoplasma, Epstein–Barr virus (EBV), anti-capsid antibodies, tropical fever panel, cytomegalovirus (CMV) immunoglobulin G (IgG) and immunoglobulin M (IgM), as well as blood cultures (aerobic and anaerobic), proteinase-3 (PR-3, cytoplasmic antineutrophil cytoplasmic antibody [c-ANCA]), and myeloperoxidase (MPO, perinuclear antineutrophil cytoplasmic antibody [p-ANCA]) were all negative. Anti-nuclear antibody (ANA) testing showed cytoplasmic speckled positivity. A positron emission tomography–computed tomography (PET–CT) scan revealed a liver abscess (amoebic) with marked hepatomegaly and an abscess in segment VIII of the liver. Intravenous (IV) metronidazole 750 mg three times daily and oral hydroxychloroquine 200 mg once daily were immediately started. CT-guided drainage of the abscess yielded around 210 mL of anchovy-sauce-like pus, which tested positive for Entamoeba histolytica (EH). The patient improved clinically, remained haemodynamically and vitally stable and was subsequently discharged.