Catamenial Pneumothorax

Catamenial pneumothorax is recurrent spontaneous pneumothorax in women, occurring within 72 hours before or after the onset of menstruation. It is the commonest feature of thoracic endometriosis syndrome, which also includes catamenial haemothorax, haemoptysis and lung nodules.

It accounts for about 3 to 6% of spontaneous pneumothorax in women of reproductive age and probably more, and is often missed for years. About 90 to 95% are right sided, with a mean age at diagnosis of 35 years. Pelvic endometriosis coexists in about a third to a half, and a history of pelvic surgery or abnormal uterine bleeding is common.

Pathophysiology. Several mechanisms are proposed: transdiaphragmatic passage of air from the peritoneal cavity through diaphragmatic fenestrations during menses (air entering via the genital tract, cervical mucus plug being absent during menses), endometrial implants on the visceral pleura or diaphragm that bleed and rupture, and prostaglandin F2 alpha induced bronchospasm and alveolar rupture. Diaphragmatic defects and endometriotic nodules are found at surgery in most patients.

Chest, shoulder or neck pain and dyspnoea, usually within 24 to 72 hours of menses onset, with cough in some. Pain often involves the right shoulder (referred from the diaphragm). Episodes recur monthly or less regularly, and some are asymptomatic. Pelvic pain, dysmenorrhoea and infertility indicate pelvic endometriosis. Rarely, haemoptysis in time with menses.

Severe dyspnoea, hypotension or haemodynamic compromise needs urgent assessment and decompression.

• Clinical diagnosis from the cyclical pattern of recurrent, usually right, pneumothorax in a woman of reproductive age. Keep a symptom diary linked to the menstrual cycle.
• Chest radiograph during an episode, with ultrasound.
• High resolution CT during or just after menses: right pneumothorax, diaphragmatic nodules or defects, subpleural nodules and sometimes a haemothorax. Imaging is best timed in the first days of menses for nodules.
• MRI of the thorax and pelvis to show endometriotic deposits on the diaphragm.
• Thoracoscopy (video assisted) is both diagnostic and therapeutic: shows diaphragmatic fenestrations (small holes, often multiple), brown or violet endometriotic nodules on the diaphragm and pleura, and pleural or liver capsule adhesions. Biopsy shows endometrial glands and stroma (CD10 and oestrogen receptor positive) but histology is positive in only a minority.
• Gynaecological assessment with laparoscopy when pelvic disease is suspected.
• Exclude lymphangioleiomyomatosis and Birt-Hogg-Dube syndrome in women with cysts.

Differential diagnosis.

• Primary spontaneous pneumothorax unrelated to menses
• Lymphangioleiomyomatosis
• Birt-Hogg-Dube syndrome
• Pulmonary Langerhans cell histiocytosis
• Pulmonary embolism, which can mimic cyclical symptoms
• Ehlers-Danlos syndrome and Marfan syndrome

• Acute episode: oxygen, needle aspiration or chest drain (10 to 14 French) for a large or symptomatic pneumothorax. Observation for small episodes.
• Definitive surgery after the first recurrence or when catamenial pneumothorax is suspected: video assisted thoracoscopic surgery, ideally in the days after menses begins (so lesions are visible), with resection or ablation of diaphragmatic endometriosis, repair or resection of fenestrations (suture, or plication, or mesh reinforcement of the diaphragm), bullectomy, and pleurodesis (mechanical abrasion or talc 4 to 5 g, or pleurectomy).
• Hormonal suppression after surgery, for at least 6 to 12 months and often longer, to cut recurrence, which is 30 to 40% without it and falls to about 10% with it: a gonadotrophin releasing hormone analogue (leuprorelin 3.75 mg intramuscularly every 4 weeks, or goserelin 3.6 mg subcutaneously every 4 weeks, for 6 months, with add back therapy to protect bone), or dienogest 2 mg orally daily, or a continuous combined oral contraceptive pill. Choice depends on fertility plans, side effects and bone health.
• Check bone density with prolonged GnRH analogue use, with calcium 1000 mg and vitamin D 800 to 1000 units daily.
• Fertility planning: gynaecology input, since hormonal therapy suppresses ovulation and pregnancy may increase recurrence in some.
• Pregnancy: pneumothorax is uncommon but can recur, and management is by chest drain, with surgery if repeated.

Complications and prognosis. Recurrence without treatment is common and over time can cause pleural scarring. Prognosis is good with surgery plus hormonal suppression.

Monitoring. Review at 3, 6 and 12 months after surgery with symptoms diary and chest radiograph, bone density every 1 to 2 years on GnRH analogue, and annual review while on hormonal therapy.

Referral and escalation. Refer to thoracic surgery and gynaecology (endometriosis service) after a suspected diagnosis, and to a fertility service when relevant.