Thoracic Endometriosis
Cyclical Chest Symptoms & Catamenial Pneumothorax — London

Endometriosis is a condition in which tissue similar to the lining of the womb grows outside it. It is common — affecting roughly 1 in 10 women of reproductive age (ESHRE, 2022) — and although it is most often found in the pelvis, it can occur in the chest. When it does, on or through the diaphragm, on the pleura (the lining around the lung), or within the lung itself, it is called thoracic endometriosis.

Because this tissue responds to the same monthly hormonal changes as the womb lining, the symptoms it causes are cyclical — they appear around the time of a period and ease off in between. That cyclical timing is the single most useful clue to the diagnosis, and it is also the one most easily missed. Thoracic endometriosis is uncommon, but it is well described: catamenial pneumothorax was first reported in the 1950s (Maurer, 1958) and the syndrome was formally defined by Joseph and Sahn in 1996. It is, in other words, a recognised condition — not a medical mystery.

Dr Okiror investigates and treats the chest manifestations of endometriosis in close collaboration with specialist gynaecologists at Guy’s and St Thomas’, so that both the chest and the underlying endometriosis are managed together rather than in isolation. Cyclical chest symptoms page →

If there is one thing worth taking from this page, it is to notice the timing of your symptoms in relation to your cycle. The patterns women describe — often for years before anyone connects them — include:

• →Chest pain during your period — often one-sided, often the right.
• →Breathlessness that comes and goes with the month — worse around bleeding.
• →Coughing up blood linked to your period (catamenial haemoptysis) — from endometrial tissue in the lung.
• →A collapsed lung around the time of your period (catamenial pneumothorax) — sometimes recurring.
• →Shoulder-tip pain with your period — from irritation of the diaphragm.

Symptoms typically cluster within about 72 hours of a period starting, and the right side is affected in the great majority of cases — around 85 to 90 per cent. Most women present in their thirties or forties, often after years of being told the symptoms are asthma, anxiety, “just bad periods”, or a recurring chest problem with no cause found. A known diagnosis of endometriosis with unexplained chest symptoms is itself a reason to investigate.

“Catamenial” simply means “related to menstruation”. A catamenial pneumothorax is a collapsed lung that recurs around the time of a period, and it is the most common way thoracic endometriosis announces itself — accounting for roughly 70 to 80 per cent of presentations.

The mechanism is mechanical. Endometrial tissue on the diaphragm can create tiny defects in it; around menstruation, air is able to pass up through these defects from the abdomen into the chest, and the lung collapses. Because the diaphragm sits a little higher on the right, and for reasons of how abdominal fluid circulates, this is overwhelmingly a right-sided problem.

It matters because catamenial pneumothorax is so often treated as ordinary spontaneous pneumothorax. In surgical series of women with recurrent spontaneous pneumothorax, a substantial proportion — commonly cited around 25 to 30 per cent — turn out to have a catamenial, endometriosis-related cause once the timing is examined. If your collapses have clustered around your periods, that pattern is the diagnosis waiting to be made. Pneumothorax page →

This is the question almost every patient arrives with, and it deserves a straight answer. The delay is not because the condition is obscure to thoracic surgeons — it is well recognised. The delay happens because the clue is a pattern that crosses two specialties.

The chest symptoms are seen by respiratory physicians or emergency teams; the periods are the territory of gynaecology; and the link between them — the cyclical timing — is easy to miss when no single clinician is looking at the whole picture at once. In the UK, endometriosis now takes an average of around nine years to diagnose (Endometriosis UK), and for thoracic endometriosis the delay is often longer still. That is a structural gap in how care is organised, not a failing on your part, and certainly not a sign your previous doctors were careless.

The practical consequence is reassuring: once the timing is joined up, the diagnosis usually follows quickly, and the treatment is effective. The most useful thing you can do is keep a simple record of when symptoms occur relative to your cycle, and raise the possibility directly. Recognising the pattern is the step that unlocks everything else.

Thoracic endometriosis sits across a line that the health system usually keeps separate, which is exactly why it needs two specialists working together rather than either one alone.

The thoracic surgeon treats the chest disease. Dr Okiror removes the endometrial deposits from the pleura and diaphragm, repairs the diaphragmatic defects, and seals the space around the lung to prevent further collapse. The gynaecologist treats the disease and its driver. Specialist gynaecologists at Guy’s and St Thomas’ provide hormonal suppression — which calms the endometrial tissue throughout the body — and manage any pelvic or abdominal endometriosis.

Neither half is complete on its own. Operating on the chest without hormonal suppression leaves the underlying tissue active and the risk of recurrence higher; suppressing hormones without repairing a leaking diaphragm leaves the mechanical problem unaddressed. The combined, planned approach is what gives the most durable result — and it is the part of the service that a thoracic surgeon working in isolation cannot easily provide.

Surgery is carried out by keyhole technique under general anaesthesia, through a few small incisions rather than an open cut — and the approach is chosen to fit the presentation. A catamenial pneumothorax, the collapsed-lung presentation, is usually treated by video-assisted thoracoscopic (VATS) keyhole surgery. Where the priority is precise removal of the endometrial deposits and repair of the diaphragm, this is done robotically — the robotic platform gives magnified, fine-detail access to the diaphragm and the back of the chest, where the disease usually sits, and allows repair work that is harder through conventional approaches.

Three things are done in the same operation. The endometrial deposits on the pleura and diaphragm are removed. Any defects in the diaphragm are repaired — direct suture for small defects, and a patch for larger ones. And the space around the lung is sealed by pleurodesis, which substantially lowers the chance of a further collapse.

Around this, the gynaecology team provides hormonal suppression and treats any pelvic or abdominal endometriosis. In plain terms: the surgery fixes the mechanical problem in the chest and removes the visible disease, while the hormonal treatment quietens the tissue so it is less likely to come back. The two together are planned from the outset, not bolted on afterwards.

Investigation begins with a careful history, timed deliberately to your menstrual cycle — when symptoms occur, on which side, and how they relate to bleeding. This history is often more informative than any single scan.

Imaging has a logic worth understanding. A CT scan is good at excluding other causes of chest symptoms, but it is not sensitive for the small endometrial deposits themselves. MRI is the more useful test for the diaphragm and soft tissue — the best non-invasive way to look for this disease — but even MRI can miss small deposits. So a normal CT, and sometimes even a normal MRI, does not rule thoracic endometriosis out. If you have had scans, it is worth asking specifically what the MRI showed, not only the CT. The definitive test is thoracoscopy (keyhole inspection of the chest), because it both confirms the diagnosis under direct vision and treats the deposits at the same time — which is why thoracic endometriosis is sometimes only confirmed at operation. In practice the diagnosis is built from the cyclical pattern, the imaging, and what is found at thoracoscopy. Diaphragmatic endometriosis →

Treatment works, and the most important message is that recurrence is something to be actively prevented rather than feared. Surgery alone — removing deposits and repairing the diaphragm — carries a higher chance of the problem returning than surgery combined with hormonal suppression, which is precisely why the combined approach is used (Alifano; Korom et al., 2004; Visouli et al., 2014).

With deposits removed, diaphragmatic defects repaired, pleurodesis performed and hormonal suppression continued for several months afterwards, the great majority of women have lasting control of their chest symptoms and a low risk of a further collapse. Two points matter for a durable result. First, the obvious holes in the diaphragm are not always the whole story: there can be weaker areas, harder to see, where the diaphragm meets the chest wall, and if these are not recognised symptoms can return even after the visible defects are repaired — part of why experience with this specific disease matters. Second, surgery is rarely a standalone fix; continuing hormonal treatment for several months after the operation is what makes the result last. Where recurrence does occur, it is usually because one element of that combined plan was incomplete — which is the argument for getting the whole approach right the first time. Dr Okiror will set out realistic expectations for your particular situation at consultation.

Many women reach this page having already had one or more collapsed lungs treated as ordinary pneumothorax, without anyone asking whether they followed the menstrual cycle. If that is you, it is worth knowing this is common and not a reason for regret — the cyclical pattern is genuinely easy to miss.

If your previous collapses clustered around your periods, or were right-sided and recurrent, a specialist review can re-examine the pattern and arrange the right imaging. A second opinion exists precisely for this situation: to look again, with the question of endometriosis specifically in mind. Request a second opinion →

If you are advocating for a thoracic referral, or are a gynaecologist considering one, the practical points are straightforward: cyclical (catamenial) chest pain, breathlessness, haemoptysis or pneumothorax — especially right-sided and within about 72 hours of menstruation — warrants thoracic assessment, whether or not pelvic endometriosis has been confirmed. Referral and treatment are coordinated jointly so the chest and pelvic disease are managed as one plan. Referral information for GPs and gynaecologists →

Investigation and treatment of thoracic endometriosis are covered by the major insurers, subject to the terms of your individual policy. Recognised by BUPA, AXA Health, Aviva, WPA, Cigna and BUPA International. Self-funding patients are also welcome, with transparent quotes provided in advance.

To confirm your specific cover, contact Jo Mitchelson, PA, on 020 7952 2882 or pa@lungsurgeon.co.uk.