Differentiating between spontaneous pneumothorax and catamenial pneumothorax in premenopausal patients can be difficult given the overlapping presentation and symptoms of these conditions. Many patients with catamenial pneumothorax are initially diagnosed with spontaneous pneumothorax until information linking the lung collapse to menstrual cycle history is obtained. Understanding the workup and treatment for both conditions is essential to providing timely care to patients who present with sudden chest pain, difficulty breathing, shortness of breath, and cough.

Primary spontaneous pneumothorax (PSP) presents without a precipitating external event and in the absence of lung disease.1 Although PSP is not associated with lung disease, 90% of patients have unrecognized lung abnormalities such as subpleural blebs and/or bullae that likely predispose patients to pneumothorax.2-4 Catamenial pneumothorax is a type of secondary spontaneous pneumothorax that is characterized by the recurrent accumulation of air in the plural cavity the day before and within 72 hours after the onset of menstruation in premenopausal patients.5 Experts believe catamenial pneumothorax is associated with thoracic endometriosis but the etiology is still not well understood. Approximately 3% to 6% of PSP occurring in premenopausal patients meets the criteria for catamenial pneumothorax; however, recent studies indicate that the rate may be as high as 35%.5

The incidence of PSP in the US has not been updated in decades and the National Institutes of Health is currently working on this data. Findings from a recent Danish study reported a PCP incidence of 12.3 cases/100,000 for males and 2.2 cases/100,000 for females.6 Risk factors for developing PSP include cigarette smoking, male sex, above-average height in men, and activities such as scuba diving, being at high altitudes, and flying.1

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Primary Spontaneous Pneumothorax

Although the etiology is not well understood and has many different components, most researchers believe that spontaneous rupture of a subpleural bleb or bulla typically causes PSP. However, it is unclear how often these lesions are actually the site of air leakage.

Many times, only a minority of the blebs are ruptured at the time of thoracoscopy evaluation or surgery.1 Another abnormality that is often present is pleural porosity, which is described as areas of disrupted mesothelial cells at the visceral pleura replaced by an inflammatory elastofibrotic layer allowing air leakage into the pleural space. These lesions may explain the high rate of recurrent pneumothorax after bullectomy (20%) without pleurodesis.7 The development of blebs, bullae, and areas of pleural porosity may be linked to a variety of factors. These include distal airway inflammation, hereditary predisposition, anatomic abnormalities of the bronchial tree, ectomorphic physiognomy with more negative intrapleural pressures and apical ischemia at the apices, low body mass index and caloric restriction, and abnormal connective tissue.1

Catamenial Pneumothorax

Three main theories behind the development of catamenial pneumothorax have been proposed. The first suggests that the increase in prostaglandin levels during ovulation causes contraction of blood vessels and bronchioles and, at the same time, sensitizes pre-existing pulmonary blebs making them more prone to rupture, which leads to rupture of alveoli and the flow of air into the pleural space.5 The second theory is that “liquefaction of cervical mucus plugs during menses allows retrograde airflow through the uterus and the fallopian tubes into the peritoneal cavity…. Through diaphragmatic defects resulting from the sloughing of endometrial implants, the air passes through into the pleural cavity causing a pneumothorax.”5 The third theory involves cyclical swelling and sloughing of thoracic endometrial implants inside terminal bronchioles causing “localized hyperinflation by a check-valve mechanism, which in turn causes a pneumothorax.”5

Clinical Presentation of Pneumothorax

Almost all patients with PSP report sudden ipsilateral chest pain, which may resolve spontaneously within 24 hours. Patients may present with dyspnea that is often mild. Although patients with PSP have no history of underlying pulmonary disease, decreased breath sounds and decreased tactile fremitus are usually present in larger pneumothoraxes and percussion is hyper-resonant.

Catamenial pneumothorax presents with ipsilateral chest pain (typically on the right side), dyspnea, and/or shoulder pain. Patients will present with symptoms that began 1 day before and within 72 hours after onset of menstruation.3 Thoracic endometriosis is defined as the presence of ectopic endometrial tissue in the thoracic cavity, which is the most frequent extrapelvic location of endometriosis.8 Endometriosis is associated with spontaneous pneumothorax; in fact, the most common manifestation of thoracic endometriosis syndrome is catamenial pneumothorax. The presence of pelvic endometriosis was reported in 55% of patients with catamenial pneumothorax, according to Gil et al.9 Endometriosis should be considered in premenopausal patients presenting with symptoms of chest pain and shortness of breath. Taking a thorough history including gynecologic history and diseases is crucial in premenopausal patients presenting with catamenial pneumothorax.

Diagnosis of Pneumothorax

Along with physical examination, diagnosis can be confirmed by an upright posteroanterior chest radiograph, which also can be used to estimate the size of the pneumothorax. In patients with a small PSP, however, computed tomography (CT) may be necessary to diagnose the presence of pleural air.1 Because of cost and access, a CT scan should only be used in unclear cases, especially in patients aged 10 to 40 years with minor pneumothorax or complex cases with additional soft tissue edema, pulmonary disease, or unsuccessful tube thoracostomy.2 Blebs and bullae seen on CT can help influence treatment choice and may indicate a more invasive, surgical approach to treatment to prevent

The diagnosis of catamenial pneumothorax is often made clinically based on patient history of shortness of breath and recurrent chest pain that is temporally related to the menstrual cycle. In these cases, CT and magnetic resonance imaging (MRI) are typically used to confirm the diagnosis of catamenial pneumothoraxes. A CT scan with contrast is usually performed first and can identify endometrial tissue/lesions on the diaphragm.9 MRI is better for diagnosing pleural nodules and diaphragmatic or hemorrhagic lesions because its sensitivity for soft tissues is superior to that of CT imaging.9 Chest radiography can diagnose pneumothorax but plays a minimal role in the diagnosis of pleural and diaphragmatic lesions, which are typically associated with catamenial pneumothoraxes. In the Gil study, diaphragmatic lesions were found in approximately 89% of cases as visualized by laparoscopy.9

Treatment of Pneumothorax

The main treatment goals of PSP are to remove air from the pleural cavity and prevent recurrence. When determining the type of intervention to perform, clinicians must consider the chance of recurrence and any associated factors leading to pneumothorax (blebs and/or bullae, catamenial pneumothorax, thoracic endometriosis). Treatment methods include conservative treatment or surgical intervention, with the most common approach to surgery being video-assisted thoracoscopic surgery (VATS, Table).9,10

pneumothorax premenopausal

If the patient is stable and the distance between the lung and chest wall is less than or equal to 2 to 3 cm, 100% oxygen, and observation are the treatment of choice.11 However, if the patient is unstable and/or the distance between the lung and the chest wall is greater than 3 cm, thoracentesis or chest tube placement is recommended.11

A study by Olesen et al compared the treatment of first episodes of PSP by simple chest tube insertion vs chest tube insertion and VATS pleurodesis. In this study, blebs were measured as less than 1 cm and greater than 1 cm. The 1-year recurrence rate was significantly lower in the intervention group compared with those who received chest tube drainage (29% vs 49%, respectively). When stratified by bullae size, VATS proved significantly better for larger bullae (≥1 cm; P =.014). The study authors observed a size-response relationship with larger bullae associated with an increased risk of recurrence.12

Recent studies have challenged the need to remove air from the pleural cavity of stable PCP patients, “introducing conservative management as a valuable therapeutic option,” noted Plojoux et al.13 Other less invasive options discussed by the authors were needle aspiration and graded talc poudrage pleurodesis to prevent recurrence.13 In patients less than age 18 years, conservative treatment was associated with a greater risk of recurrence compared with patients who underwent surgery.14 Multiple studies have also shown that surgery reduces ipsilateral recurrence in

VATS pleurodesis or chemical pleurodesis to prevent a future recurrence is recommended in all patients with a recurrent PSP, with an initial spontaneous pneumothorax that required VATS or tube thoracostomy/blebectomy, and who have an occupation or hobby where the risk of recurrence is increased (eg, a pilot or scuba diver).11

For patients diagnosed with catamenial pneumothorax and/or thoracic endometriosis who have a high probability of recurrent pneumothorax, surgical intervention should be considered as a first-line therapy to lessen the chance of recurrence compared with medical treatment only.8 In the patient population with thoracic endometriosis associated with catamenial pneumothorax, surgical treatment combined with hormone therapy is associated with better results than surgery alone.5

Postoperative treatment of catamenial pneumothorax with gonadotropin-releasing hormone (GnRH) agonists or oral contraceptives similar to that for pelvic endometriosis can be administered for symptom relief and reduce recurrences as well as suppress concomitant pelvic endometriosis.9 In premenopausal patients who don’t wish to conceive and are diagnosed with catamenial pneumothorax that is endometriosis related or nonendometriosis related, hormonal therapy/ovulatory suppressants as preventive therapy for future recurrence should be


The prognosis is very good in patients who receive timely treatment, which prevents progression to potentially life-threatening tension pneumothorax and obstructive shock. To ensure pneumothoraxes are not missed, clinicians should have a low threshold to evaluate for SPS in a patient who presents with dyspnea and chest pain.10 In the case of a premenopausal woman who presents with dyspnea and chest pain, the clinician should suspect catamenial pneumothorax and capture their menstrual history.

Recurrence rates range from 14% to 55% over 1 to 5 years but the highest risk is within the first 30 days.9,11 It is ­important to identify risk factors for reoccurrence early, so proper treatment can be performed to prevent reoccurrence. Identification of blebs and bullae, catamenial pneumothorax, and endometriosis-related pneumothorax all increase the risk of reoccurrence and, therefore, require more invasive/surgical treatment. Missed or improper diagnosis of these specific conditions can lead to what could have been a preventable reoccurrence, further procedures, and hospital stays.

Carlie Overley, PA-C, works with the Advanced Neurosurgery Associates team at Northside Hospital in metropolitan Atlanta, GA. She recently graduated from Augusta University’s Physician Assistant program as a member of the Alpha Eta National Honor


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14. Ng GYH, Nah SA, Teoh OH, Ong LY. Primary spontaneous pneumothorax in children: factors predicting recurrence and contralateral occurrence. Pediatr Surg Int. 2020;36(3):383-389. doi:10.1007/s00383-020-04619-x