Computed tomography imaging characteristics of paradoxical reactions in perihepatic and hepatic tuberculosis.

Background: Hepatic and perihepatic tuberculosis (TB) are rare forms of extrapulmonary TB. Paradoxical reactions, characterized by the enlargement of existing lesions or the appearance of new lesions during anti-TB treatment, are uncommon in hepatic TB. This study aimed to retrospectively analyze the computed tomography (CT) imaging characteristics of paradoxical reactions in hepatic and perihepatic TB to enhance the understanding of this condition. Methods: We conducted a retrospective review of the data of patients diagnosed with perihepatic and hepatic TB at the Kunming Third People's Hospital from January 2020 to June 2024. We selected patients with follow-up CT imaging showing paradoxical reactions, and we summarized their initial CT findings, paradoxical reaction CT manifestations, and follow-up CT presentations. Results: The data of 37 patients with perihepatic and hepatic TB and CT follow-up imaging were collected. Of the 37 patients, 14 (37.8%) exhibited paradoxical reactions characterized by an enlargement of existing lesions or the appearance of new lesions on review. Among these 14 patients, 7 were male, 7 were female, with ages ranging from 17 to 46 years (median age: 23 years). Twelve patients had concurrent pulmonary TB, and 13 patients had other extrapulmonary TB. Thirteen patients tested positive for TB infection by interferon-gamma release assay, and eight had positive etiological results. Twelve patients showed a decrease in CD4+ T-cell counts. The time to the paradoxical reaction onset after initial diagnosis ranged from 13 to 183 days (median time: 82 days). The initial CT presentations of these 14 patients included 11 cases of perihepatic peritoneum/hepatic capsule linear or nodular thickening (capsular type), and three cases of combined perihepatic peritoneum/hepatic capsule linear or nodular thickening with hepatic parenchymal lesions (mixed type). Capsular-type paradoxical reactions manifested as new or enlarged nodules of the perihepatic peritoneum/hepatic capsule and intrahepatic lesions, with marked ring enhancement on enhanced scans. Mixed-type paradoxical reactions showed significant enlargement of perihepatic peritoneum/hepatic capsule lesions and intrahepatic lesions, with the enhanced scans showing higher ring enhancement than that in the initial presentation. Among the 12 patients with long-term follow-up data, lesion improvement began at 6 to 20 months (median time: 12 months). CT imaging showed gradual lesion size reduction, decreased ring enhancement density, an absence of ring enhancement, and lesion calcification. Conclusions: During anti-TB treatment, perihepatic and hepatic TB patients can show paradoxical reactions, which often present as ring enhancement. After treatment, these paradoxical reaction lesions can show improvement. CT-enhanced scans have diagnostic value in the occurrence and progression of perihepatic and hepatic TB.