Bilateral Inferior Accessory Fissures in Lungs

CLINICAL PRESENTATION A 67-year-old woman was referred for evaluation of bilateral linear streaks over both lower lung fields on chest radiography (Figure 1A), which was incidentally noticed in the health examination. She was a nonsmoker and did not have cough, sputum, fever, dyspnea or chest pain. On physical examination, the chest wall expanded symmetrically and the breathing sounds were clear on auscultation of bilateral lung fields. Chest computed tomography (CT) revealed 2 thin white lines, arising from the mediastinum and extending posteriorly over both lower lobes (Figure 1B). Therefore, the diagnosis of the bilateral accessory fissures in the lower lobes was confirmed. Accessory fissure in the lung, defined as a cleft of varying depth lined by 2 layers of visceral pleural, is the most common variation of lung specimens. However, its presence is often neglected or misinterpreted on chest radiography or even CT. Ariyurek et al reviewed high-resolution CT scans of 186 patients and reported that a total 69 accessory fissures were detected in 59 (32%) patients. In another prospective study of 115 patients, 44 accessory fissures were noted in 35 (30.4%) patients by highresolution CT. In addition, inferior accessory fissure was the most common accessory fissure, followed by the left minor fissure in both studies. Although the clinical significance of accessory fissures is limited, recognizing this normal variation would be helpful in segmental localization of pulmonary lesions and the extent of pulmonary disease. Furthermore, the appreciation of the characteristic radiological findings of this normal anatomical variant could allow clinicians to avoid diagnosing accessory fissures as pathological structures.