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PURPOSE: Our goal was to determine the prevalence of intrathoracic lymphadenopathy on chest CT in patients with empyema. METHOD: We retrospectively identified 27 patients (14 men, 13 women, mean age 43 years) with nontuberculous empyema examined with chest CT. All scans were reviewed by two of three board-certified radiologists for the presence of intrathoracic lymphadenopathy (> or = 1 cm, short axis) in an American Thoracic Society (ATS) nodal station or the internal mammary region. Differences were resolved by consensus. RESULTS: Thirteen (48%) patients with empyema had lymphadenopathy on chest CT. The mean number of enlarged lymph nodes for the patients with lymphadenopathy was 3.2 (SD +/-2.3, range 1-8). The mean size of the largest lymph node was 1.4 cm (range 1.0-2.5 cm). The lymphadenopathy was unilateral and ipsilateral to the empyema in seven (54%), bilateral in five (38%), and unilateral contralateral to the empyema in one. The distribution of lymphadenopathy according to ATS nodal stations was 4R (n = 8), 7 (n = 6), 10R (n = 5); n = 2 each 2R, 10L, 11L; and n = 1 each 11R, 2L, 4L, and 6. Four patients had internal mammary lymphadenopathy. Pleural fluid and smooth pleural thickening were present in each case. Four patients had follow-up CT after treatment. There was a decrease or resolution of the lymphadenopathy in each case. CONCLUSION: Intrathoracic lymphadenopathy is a common CT finding in patients with empyema and occurred in 48% of this series. In patients with smooth pleural thickening and pleural effusion, intrathoracic lymphadenopathy should not be used as a criterion to differentiate empyema from malignant or tuberculous pleural effusion.