A chest CT should be obtained in this patient with nonresponsive pneumonia. He presents with severe community-acquired pneumonia (CAP) and has been treated with appropriate empiric antibiotics. Most patients with uncomplicated CAP will show improvement in clinical symptoms (fever, cough, dyspnea) within 2 to 3 days; nonresponsive pneumonia is defined as a lack of significant clinical response within 72 hours of initiating therapy. Chest CT or, possibly, high-resolution chest CT is the usual initial radiographic study used to evaluate patients with nonresponsive pneumonia. Compared with plain chest radiography, chest CT provides improved detection of parenchymal abnormalities, including foci of infection such as a lung abscess or cavitary lesions and occult empyema. These findings may help guide additional therapy, or CT may identify other causes of failure to improve that were not previously considered, particularly in a patient whose baseline plain radiograph may be difficult to interpret.

Fiberoptic bronchoscopy with bronchoalveolar lavage and transbronchial biopsy may be helpful in the diagnosis of nonresponsive pneumonia but is typically performed after chest CT, particularly if there are findings (focal areas of fluid collection or consolidation or lymphadenopathy) that help guide bronchoscopic evaluation or be amenable to bronchoscopic biopsy.

Chest ultrasonography is used primarily to diagnose pleural effusions and guide therapeutic thoracentesis and may be helpful in diagnosing pleural abnormalities such as thickening or nodules. It is less helpful for evaluating the lung parenchyma. This patient has not had evidence of pleural effusions on chest radiography, so the diagnostic yield of chest ultrasonography would be low, particularly compared with chest CT.

More invasive biopsy procedures such as thoracoscopic or open lung biopsy are typically reserved for instances when a specific disorder requiring direct tissue evaluation is needed or if other diagnostic interventions are unrevealing in a patient requiring a diagnosis. Therefore, lung biopsy would not be an appropriate next step before additional imaging.