Abstract
Catamenial pneumothorax occurs during the menstrual cycle. Of the 6 patients who underwent surgical treatment, 5 had bullae of the right middle lobe ridge in the interlobar fissure. Two of them also had obvious air leaks intraoperatively and demonstrated endometrial tissue in the resected specimen. Our findings suggest that it is necessary to confirm the right middle lobe ridge in the interlobar fissure of patients with catamenial/endometriosis-related pneumothorax.