Pleural Endometriosis

Pleural endometriosis is the presence of endometrial tissue on the pleural surface, causing cyclical bleeding into the pleural space (catamenial haemothorax) and, less often, pleural nodules and chest pain. It is part of thoracic endometriosis syndrome, and is the second commonest form after catamenial pneumothorax.

It affects women of reproductive age, with a mean age of about 35 years, and is right sided in over 90%. Pelvic endometriosis or a history of uterine surgery is present in a half. It is probably underdiagnosed, and diagnosis is delayed by 2 or more years on average.

Pathophysiology. Endometrial tissue reaches the pleura by retrograde menstruation through peritoneal fluid and diaphragmatic defects, by lymphatic or vascular spread, or by metaplasia of coelomic epithelium. The implants respond to hormones, bleed at menses and cause blood stained effusion, nodules and adhesions.

Pleuritic chest, shoulder or scapular pain and breathlessness starting within 72 hours of menstrual onset, with relief after menses. Examination shows dullness and reduced breath sounds over the effusion. Some have a blood stained effusion with no cyclical link, or a chronic pleural thickening. Cough or haemoptysis suggests parenchymal disease.

Severe dyspnoea, tachycardia or haemodynamic instability suggests a large haemothorax and needs urgent drainage.

• Cyclical symptoms in a woman of reproductive age with a right sided effusion, which are the key clue, and a symptom diary helps.
• Pleural fluid: blood stained exudate with red cells, neutrophils or lymphocytes, and no malignant cells. Tests for tuberculosis and infection are negative. Haematocrit of the fluid may be high.
• Chest radiograph and ultrasound: unilateral right effusion, varying with the cycle. CT and MRI: pleural and diaphragmatic nodules, thickening, subpleural nodules or cysts, and effusion. MRI shows haemorrhagic foci (high T1 signal).
• Thoracoscopy: haemorrhagic or brown blue nodules on the pleura and diaphragm, and diaphragmatic defects. Biopsy shows endometrial glands, stroma and haemosiderin laden macrophages (CD10 and oestrogen receptor positive), though yield is limited.
• Gynaecological evaluation, with pelvic MRI or laparoscopy.
• Exclude malignancy, tuberculosis, pulmonary embolism, and other causes of haemothorax.

Differential diagnosis.

• Malignant pleural effusion or mesothelioma
• Tuberculous pleurisy
• Traumatic or spontaneous haemothorax
• Pulmonary embolism with infarction
• Lymphangioleiomyomatosis (chylous effusion, cysts)
• Hepatic hydrothorax

• Acute haemothorax: oxygen, thoracentesis or small bore drain (14 to 20 French) for symptomatic effusion, blood transfusion if bleeding is large, and analgesia (paracetamol 1 g every 6 hours, ibuprofen 400 mg every 8 hours with food).
• Hormonal suppression for at least 6 to 12 months: a gonadotrophin releasing hormone analogue (leuprorelin 3.75 mg intramuscularly every 4 weeks, or goserelin 3.6 mg subcutaneously every 4 weeks, for up to 6 months with add back therapy), dienogest 2 mg orally daily, or a continuous oral contraceptive. Hormonal therapy alone has a high recurrence once stopped, and it is also used before and after surgery.
• Surgery by video assisted thoracoscopy: excision or ablation of pleural and diaphragmatic implants, repair of diaphragmatic defects, pleurectomy or pleurodesis (talc 4 to 5 g), which reduces recurrence more than drainage alone.
• Protect bone health on GnRH analogues: calcium 1000 mg and vitamin D 800 to 1000 units daily, and bone density testing at 1 to 2 years.
• Fertility counselling with gynaecology, since the disease often coexists with pelvic endometriosis, and hormonal treatment prevents ovulation.

Complications and prognosis. Recurrent haemothorax, pleural adhesions, fibrothorax and trapped lung. Recurrence after hormones alone is about 50% within a year of stopping and falls to about 10 to 20% after surgery with hormones.

Monitoring. Review every 3 months in the first year with a symptom diary and chest imaging, bone density in long term treatment, and gynaecological follow up.

Referral and escalation. Refer to a thoracic surgeon and a gynaecologist with endometriosis expertise, and to haematology for severe bleeding.