Introduction:
Thoracic endometriosis is a complex condition with several complications. Their diagnosis is often missed and results in complications and recurrent hospitalizations. The condition is characterized by the presence of endometrial tissues (lining layer of uterine tissues) outside the uterus in the chest cavity surrounding the lungs. It is estimated to be seen in six to ten percent of women in the reproductive age group. Endometrial tissue within the lungs, on the diaphragm, and on pleural surfaces produce a spectrum of clinical and radiological features.
What Is Thoracic Endometriosis Syndrome?
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Endometriosis, as the word suggests, is the growth of endometrial tissue (the layer lining the uterine tissue) outside the uterine cavity. It is a common condition and affects more women in the reproductive age group than the estimated incidence of six to ten percent. Among the affected women, 12 % of the cases are seen in non-reproductive organs, called extragenital endometriosis. The thoracic cavity is the most common site of endometriosis outside the abdominopelvic cavity. The presence of endometrial tissue in the lung parenchyma (alveoli of the lungs), the pleural surface, and the diaphragm produce a spectrum of clinical manifestation which include
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Catamenial Pneumothorax: Accumulating air in the pleural cavity of women in their reproductive age without any underlying respiratory disease.
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Catamenial Hemothorax: Accumulating blood in the space between the chest wall and lungs in menstruating women.
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Catamenial Hemoptysis: The presence of blood-tinged sputum most associated with menstruation.
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Pulmonary Nodules: Clumps of cells in the lungs.
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Together these features result in a phenomenon called thoracic endometriosis syndrome. Recent studies have expanded the classification of thoracic endometriosis syndrome to include endometriosis-related diaphragmatic hernia (a hole in the diaphragm that enables the content of the abdominal cavity to move into the chest cavity), endometriosis-related pleural effusion (accumulation of fluid in the pleural cavity), and catamenial chest pain (chest pain associated with menstruation).
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Currently, thoracic endometriosis is considered a manifestation of the progression of endometriosis. It has an older age of onset compared to pelvic endometriosis. Pelvic endometriosis is usually presented at a mean age of 25, whereas thoracic endometriosis is presented at a mean age of 35. It is usually associated with reproductive, genitourinary, and gastrointestinal endometriosis, though it may occur in isolation too. Among the patients diagnosed with thoracic endometriosis, 50 to 84 % of the cases are associated with concomitant pelvic endometriosis.
What Is the Pathophysiology of Thoracic Endometriosis?
Several theories have been put forward to explain the pathogenesis of thoracic endometriosis. However, none of them could explain the exact pathology for all the clinical manifestations of thoracic endometriosis syndrome.
Retrograde Menstruation Theory:
The theory is otherwise known as Sampson's theory of retrograde menstruation. The theory states that the endometrial cells move through the fallopian tubes into the peritoneal cavity and get implanted on the peritoneal surfaces. They further undergo retrograde movement to reach the subdiaphragmatic movement to either implant on the diaphragm or migrate to the pleural cavity through the fenestrations in the diaphragm.
Coelomic Metaplasia Theory:
The theory states that thoracic endometriosis arises from the metaplasia of the mesothelial cells that lines the pleural and peritoneal surface into endometrial tissues. Physiological stimuli like estrogen influence mesothelial metaplasia. Some rare cases of endometriosis have been observed in men receiving high doses of estrogen.
Lymphatic and Hematogenous Dissemination Theory:
This theory states that implantation of endometrial tissues occurs by the endometrial cells that are carried by blood (hematogenous) or lymphatic route to the chest cavity. The theory gives a possible explanation for bronchopulmonary endometriosis. Further evidence supporting the theory is endometriosis in distant locations of the body, like the brain and bone.
Prostaglandin Theory:
The theory of prostaglandins suggests that thoracic endometriosis is associated with prostaglandin F2 alpha (a potent bronchial and vascular constrictor) present in the plasma of menstruating women. During menstruation, the concentration of circulating prostaglandin F2 alpha increases, resulting in the constriction of blood vessels and the bronchioles, which leads to the rupture of alveolar blebs and bullae, resulting in a catamenial pneumothorax.
What Are the Signs and Symptoms of Thoracic Endometriosis?
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Thoracic endometriosis has a variable clinical presentation. Many patients are asymptomatic. Common symptoms are catamenial pneumothorax, catamenial hemothorax, hemoptysis, and pulmonary nodules. The symptoms are reported during the periovulatory period and after sexual intercourse.
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The anatomic location of the endometrial tissue determines symptoms. Endometriosis on the pleura is typically presented with catamenial pneumothorax. It is the recurrent occurrence of pneumothorax within 72 hours of the onset of menstruation. The patient experiences pleuritic chest pain, shortness of breath, and cough. Catamenial hemothorax is less commonly seen in pleuritic endometriosis. In bronchopulmonary endometriosis, catamenial hemoptysis and pulmonary nodules of size between 0.5 to 3cm are observed in radiographs. Diaphragmatic endometriosis is usually asymptomatic but may sometimes cause irritation of the phrenic nerve resulting in symptoms like cyclic shoulder, neck, and epigastric pain.
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Though a temporal association of the symptoms with menstruation is not always recognized, a high suspicion level is necessary for an early diagnosis. However, the features distinguishing thoracic endometriosis from diseases of the same clinical presentation are its association with menstruation, young age, and a history of infertility.
How Is Thoracic Endometriosis Managed?
The first line of treatment involves suppressing the steroid hormones produced by the ovaries. Gonadotropin-releasing hormone analogs suppress ectopic endometrial growth. However, they have adverse effects like early menopause and osteoporosis. Discontinuation of suppressive therapy is associated with a high incidence of recurrence. In such patients, surgical treatment is considered.
Thoracic endometriosis and pelvic endometriosis are often concomitant, and a multidisciplinary surgical approach is used to treat the disease in a single procedure to produce the most effective outcome.
Conclusion:
Thoracic endometriosis, although rare, can produce debilitating symptoms in some affected individuals. Since the symptoms are not exact, patients presented must be examined with a high degree of suspicion. Most often, thoracic and pelvic endometriosis occur together, and pelvic endometriosis treated surgically must be examined thoroughly for the presence of diaphragmatic lesions. A combination of medical, surgical, and post-operative hormonal therapy is required to correct and prevent the recurrence of the condition.
