In a minority of patients the disease does recur. Most cases of recurrence are not in fact true recurrence but are in fact disease persistence. It is far more common for an area of disease to be missed or only partially removed than for new disease to occur and most cases of “recurrent” endometriosis after surgery are examples of disease persistence due to incomplete removal of the disease. In such cases, thorough excision of all remaining disease will provide ongoing resolution of the disease. The problem of incomplete surgery lies at the heart of the belief that endometriosis is an incurable disease that always comes back. This is why patients who find themselves on a seemingly never ending carousel of repeated surgeries should start questioning how complete their surgery has been and whether their surgeon is sufficiently skilled to offer them optimal surgical care.
In rare cases, however, the disease may recur despite thorough excision surgery. Clinical observations made during second look procedures reveal that recurrence following excision surgery tends to occur at the margins of previous areas of excision. It is far less common for the disease to recur in new sites. Furthermore, recurrent disease tends to be more limited in presentation than the original manifestation of the disease (women with recurrent disease typically have less disease than at the time of their first surgery and recurrent disease is superficial). One possible explanation for the patterning of recurrence at the margins of previously excised areas is that the healing process itself may trigger vulnerable tracts of tissue that contain a latent potential to become endometriosis to then transform into new areas of subtle disease in some patients. Performing excision with wide margins around the areas of visible disease can help reduce the risk of recurrence.
The youngest patients may be at greater risk of disease recurrence although the data are mixed. A recent study found no recurrence in a small series of teenage patients following broad excision. Younger patients may present with more subtle presentations of the disease that are easier to overlook or areas of healthy appearing tissue may still harbor a latent potential to subsequently transform into endometriosis through a process of metaplasia (where one tissue type transforms into another tissue type). It is therefore important to treat endometriosis in teenagers with broad excision to minimize the risk of the patient later having to return for further surgery. Even in teenagers, most patients will experience complete and ongoing resolution of their disease following a single surgical excision procedure.
The sites in the body most likely to undergo “recurrence” following surgery are in fact the ovaries. In the case of ovarian disease deep within the ovarian tissue it may be difficult if not impossible to detect small focal areas of disease during surgery. Ovarian endometriomas can be excised but sometimes a patient will have other small areas of disease within the ovary that are only detected if they later develop into new endometriomas. The rate of recurrence following excision of an endometrioma (cystectomy) is estimated to be around 5%. Obviously the risk of recurrence varies depending on the skill of the surgeon.
Recurrence of deep disease is extremely rare. If an area of deep endometriosis is found following previous surgery it is highly likely that the initial surgery failed to completely remove the lesion.