Endometriosis gets its name from the endometrium, which lines the inside of the uterine cavity. With endometriosis, there is ectopic endometrial tissue, which means endometrium can be present in other parts of the body, like the ovaries or fallopian tubes, or even as far as the lungs! Also, with endometriosis, the ectopic tissue behaves just like regular endometrium would, and it undergoes cyclic changes in response to the menstrual cycle.
Now, let’s look at the overall anatomy and physiology of the uterus. Remember that the uterine wall is comprised of three layers: the endometrium, which is the innermost, mucosal layer, and is itself made up of a basal layer, and a functional layer; the myometrium, which is the strong smooth muscle that gives the uterine wall its thickness; and the perimetrium, which is the outermost layer, and it’s basically a continuation of the peritoneal lining.
Now, during each menstrual cycle, an egg is released from the ovaries at ovulation, and estrogen and progesterone levels increase. Estrogen thickens the functional layer of the endometrium to prepare it for implantation. If there is no fertilization, hormone levels drop, and the functional layer sloughs off, and is eliminated along with a small amount of blood during menstruation. And after menstruation, the cycle repeats itself all over again!
Okay, now, the exact cause behind endometriosis is still unknown, but there are few theories that try to explain this phenomenon. One such theory is retrograde menstruation, which suggests that during menstruation, some blood and endometrial cells could flow backwards into a fallopian tube and implant into the nearby pelvic tissues.
Next, there is the benign metastases theory, which suggests that endometrial cells can travel to distant organs like the heart or lungs through lymph and blood, while some theories blame it on genetics, immunity and abnormal hormonal patterns. In addition to these proposed causes, there are some risk factors for developing endometriosis. These include a family history of endometriosis, never having been pregnant, early menarche, and late menopause.
Now, let’s discuss the pathophysiology of endometriosis. Once the migrated endometrial cells have implanted elsewhere, they begin to release proinflammatory factors. Inflammation promotes the growth of new blood vessels that deliver blood and oxygen to the ectopic endometrial tissue. As it grows, the implant starts behaving exactly like the endometrium of the uterus. So in response to estrogen, it thickens, and when hormone levels drop, it sloughs off and bleeds a little, only to regenerate with the next menstrual cycle. In some clients, chronic inflammations and adhesions can damage the reproductive structures, thus inhibiting the release of the egg or its movement through the fallopian tube. As a result, infertility may occur.
Finally, a particular scenario is when there is ectopic endometrial tissue on an ovary. This can cause the formation of an endometrioma, also called a chocolate cyst, because it contains old, dark blood, as well as shed tissue. When these get too large, they can rupture and spill their contents, causing inflammation and pain. Alternatively, a large endometrioma can cause ovarian torsion, which is when the ovary twists around its vascular support, blocking blood flow.
The clinical manifestations of endometriosis vary depending on the location of ectopic endometrial tissue, but the most common symptom is pain, which can sometimes be quite debilitating.
Endometriosis on the reproductive organs causes pelvic pain, excessive menstrual bleeding and painful menstruation, as well as painful sexual intercourse, which is called dyspareunia. Other manifestations include painful urination and defecation, as well as abdominal pain. In the rare case of lung endometriosis, clients may cough up blood during their monthly menstrual cycle. All of these manifestations often vary with the hormone changes throughout the menstrual cycle, and they tend to get worse during menstruation. Finally, endometriomas can be associated with unilateral pelvic pain, which can be acute and severe in case of ovarian torsion.
So, the diagnosis of endometriosis starts with the client’s history and physical assessment. Abnormal pelvic examination findings include tenderness on palpation, as well as focal pain or a palpable mass that could suggest an endometrioma. Other investigations can include an ultrasound or MRI. Finally, laparoscopy can be performed and the diagnosis can be confirmed with a biopsy of the implanted tissue.