Imaging of the axillary subsegment of the right upper lobe.

The bronchial supply of the lateral or axillary area of the right upper lobe is variable. In 16 percent of normal subjects, an independent ramus of the posterior right upper lobe bronchus supplies an axillary subsegment. Airspace disease in the axillary subsegment has a characteristic appearance on radiographs. The CT appearance of disease in the axillary subsegment correlates closely with classic anatomic studies. Recognizing that disease is located in the axillary subsegment can help in directing bronchoscopy or biopsy.