Image Characteristics of Lung Abscess by Convex-Probe Endobronchial Ultrasound

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To the Editor:
A 53-year-old man with a history of emphysema was referred to our cancer center for a right lower lobe lesion that was incidentally found on computed tomography imaging (Fig. 1A) performed for evaluation of abdominal pain. He denied any dyspnea or hemoptysis but had a dry cough and 30-pound weight loss over several months. On bronchoscopic examination, the airway appeared edematous with a significant amount of purulent secretions emanating from the right lower lobe bronchus. Convex-probe endobronchial ultrasound (CP-EBUS) was used to perform transbronchial needle aspiration (TBNA) of enlarged mediastinal and hilar lymph nodes. The CP-EBUS was then wedged in the right lower lobe lateral segments, and the lesion was visualized. The endoscopic ultrasound image was consistent with hyperechoic and multiple cystic-like echoic areas with a clear margin (Fig. 2A–C). The color Doppler mode showed no evidence of vascularization (Fig. 2D). EBUS-TBNA of the right lower lobe was performed along with bronchioalveolar lavage of the right lower lobe. The TBNA of lymph nodes showed no evidence of malignancy and that of the mass showed acute inflammatory infiltrate. Bronchioalveolar lavage showed marked acute inflammatory cells with degenerative changes and cultures grew ampicillin-susceptible Hemophilus influenza. The patient was treated with a 2-week course of amoxicillin/clavulanic acid. Follow-up using chest computed tomography scans showed near resolution of the right lower lobe lesion, which remained stable at 2 years’ follow-up (Fig. 1B).
Over the past decade, CP-EBUS has become the procedure of choice for the diagnosis and staging lung cancer.1 It is routinely used for the diagnosis of other benign, malignant, and vascular conditions such as sarcoidosis, lymphoma, and vascular tumors.2,3 Lung abscess is defined as the necrosis of parenchyma caused by microbial infection. It is sometimes difficult to differentiate a lung abscess from lung cancer without histopathologic evaluation. Often with malignancy, the endobronchial involvement leads to postobstructive pneumonia and vascular invasion by tumor results in tumor necrosis, which may progress to a suppurative lesion.4 In our case, the biopsies were negative for malignancy, and there were no endobronchial lesions. Given the near resolution of the lung lesion after antibiotic therapy, the diagnosis was highly suggestive of lung abscess. These images are similar to a previously described case by our group in which, the lung abscess was diagnosed after bilobectomy for the management of the abscess that was refractory to many courses of intravenous and oral antibiotics.5 The hyperechoic and cystic-like areas are probably consistent with thick purulent regions and necrotic pockets inside the lesion, respectively. Recognizing the characteristics of CP-EBUS image for lung abscess may guide the endoscopist and the treating physicians in their differential diagnosis and therapeutic planning. By reporting this case of CP-EBUS image of lung abscess, we aim to help and guide the bronchoscopist in making the diagnosis and treatment of lung abscesses.

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