Third time’s the charm

Catamenial pneumothorax is defined as a spontaneous and recurrent pneumothorax (at least two episodes) that occurs between the day before and 72 h after the onset of menstruation [ 1 – 4 ]. Some extend it to 72 h before [ 4 ] and others to 96 h after [ 5 ]. It represents 3–6% of spontaneous pneumothoraces in women of childbearing age [ 4 ,  6 , 7 ]. In studies evaluating only women referred for thoracic surgery, the proportion was 25–33% [ 1 , 5 , 8 ]. Endometriosis refers to endometrial tissue outside the uterus, more frequently in the pelvic peritoneum, ovaries and rectovaginal septum. In rare cases, it can occur outside the pelvic cavity, mainly in the thoracic cavity [ 9 , 10 ]. The most frequent clinical manifestation is catamenial pneumothorax (72%) followed by haemoptysis (14%), haemothorax (12%) and pulmonary nodules (2%) [ 11 ]. Endometriosis affects 2–10% of women of childbearing age [ 9 , 12 ]. Despite being considered rare, the true prevalence of thoracic endometriosis is unknown. Thoracic endometriosis incidence peaks around 35 years of age, 5 years after the peak incidence of pelvic endometriosis [ 13 ]. Definitive diagnosis requires identification of characteristic macroscopic lesions (endometrial foci, frequently on the diaphragm, and diaphragmatic defects) and histopathological confirmation. In this case, the diagnosis was only possible after a second thoracic surgery, demonstrating how difficult it can be. In addition, she had pelvic disease that required specific therapy, showing how valuable an interdisciplinary approach is. The pathophysiology of catamenial pneumothorax is poorly understood. The most accepted theory states that during menstruation, there is no cervical mucus so the peritoneal cavity communicates with exterior through the uterus and Fallopian tubes. Consequently, air can enter pelvic cavity and, through congenital or acquired diaphragmatic defects, it can reach pleural cavity. Being endometriosis characterised by diaphragmatic defects, this theory explains its association with catamenial pneumothorax. Like catamenial pneumothorax, there are numerous theories that attempt to explain the pathophysiology of thoracic endometriosis. The most accepted one is based on retrograde menstruation. Retrograde menstruation leads to pelvic implantation of endometrial tissue. There is a preferential circulation of fluids/air from right paracolic gutter to right subphrenic space. Here, the liver and the pressure difference between pelvic and thoracic cavities result in migration of fluids/air from the right subphrenic space to right pleural space, explaining why catamenial pneumothorax is right sided in 85–90% of cases [ 4 ]. There is no consensus on the best therapeutic approach in catamenial pneumothorax, because published data are based on small retrospective studies and case reports [ 1 , 2 , 4 , 5 ]. Nevertheless, most experts advocate both medical and surgical approaches in order to minimise recurrences. The thoracic cavity must be carefully inspected and any lesions (endometrial foci, blebs or diaphragmatic defects) resected [ 5 , 8 ], preferably by pleurectomy because it will promote pleurodesis. Chemical basal pleurodesis can also be performed to prevent chronic hiccups. The literature also refers to other techniques such as exclusive chemical pleurodesis with talc [ 1 ] or placing an artificial web above the diaphragm whenever diaphragmatic defects are found [ 2 , 5 ]. Medical therapy aims at endometrial atrophy and amenorrhoea by means of hormonal blockage. Amenorrhoea should be maintained 6–12 months after surgery in order to allow an efficient pleural adhesion [ 3 , 4 ]. Premature interruption of hormonal therapy can lead to cyclic hormonal changes and pneumothorax recurrence. There are several hormonal therapies: oral contraceptives, danazol, progesterone derivatives and gonadotropin-releasing hormone analogues. Oral contraceptives have high recurrence rates. This patient had three catamenial pneumothoraces despite taking oral contraceptives for >20 years. We hypothesise that oral contraceptives were a protective factor, delaying disease progression and explaining why she is considerably older than we would expect. Although there have been no comparative studies of efficacy, several experts prefer gonadotropin-releasing hormone analogues [ 2 ,  4 ,  5 ,  13 ]. However, we have to consider their long-term adverse effects, particularly on bone density, and their significantly higher cost. Accordingly, in this case, a progesterone derivative was chosen as first-line therapy. After deep pelvic endometriosis with possible rectal extension was diagnosed in this multiparous woman not planning another pregnancy, a surgical approach was proposed. Hormonal therapy became a short-term plan (until surgery) and concerns about its long-term use were less important. Therefore, the progesterone derivative was replaced by a gonadotropin-releasing hormone analogue, goserelin. In conclusion, thoracic endometriosis diagnosis is difficult and requires high clinical suspicion. In women with recurrent pneumothoraces, a temporal relationship with menstruation, right-sided predominance and gynaecological symptoms should alert us to this diagnosis.