The diaphragm is really the “breathing muscle” and sits at the top of the abdominal cavity. There are two halves to the diaphragm, though it is virtually always the right-hand side that can be affected by endometriosis.
In these cases patients present with cyclical pain in the upper right side of the abdomen, with pain coinciding with the menstrual cycle in most situations. In relatively uncommon situations the pain may be near continuous.
The organs in closest proximity to the right hemi-diaphragm include the liver and gall bladder; it is the latter organ that is most often attributed to causing this sharp pain, which limits the ability to take in a deep breath or exercise. Pleuritic chest pain (inflammation of the outer lining of the lung) can also mimic this pain and is seen rarely in patients with severe pelvic endometriosis.