This is not really related to Yin Yoga as we rarely, with the exception of Snail Pose, do inversions, but here are a few thoughts on your question. First let's define our terms: here is the definition of endometriosis from the Mayo Clinic
- Endometriosis (en-doe-me-tree-O-sis) is an often painful disorder in which tissue that normally lines the inside of your uterus...the endometrium ... grows outside your uterus (endometrial implant). Endometriosis most commonly involves your ovaries, bowel or the tissue lining your pelvis. Rarely, endometrial tissue may spread beyond your pelvic region. In endometriosis, displaced endometrial tissue continues to act as it normally would ... it thickens, breaks down and bleeds with each menstrual cycle. Because this displaced tissue has no way to exit your body, it becomes trapped. When endometriosis involves the ovaries, cysts called endometriomas may form. Surrounding tissue can become irritated, eventually developing scar tissue and adhesions ... abnormal tissue that binds organs together. Endometriosis can cause pain ... sometimes severe ... especially during your period. Fertility problems also may develop.
Commonly in yoga classes, women are requested to do no inversions during their periods if they suffer endometriosis because it can exacerbate the problem. One of the main causes of endometriosis is retrograde menstruation. Again, from the Mayo Clinic:
- Retrograde menstruation is the most likely explanation for endometriosis. In retrograde menstruation, menstrual blood containing endometrial cells flows back through the fallopian tubes and into the pelvic cavity instead of out of the body. These displaced endometrial cells stick to the pelvic walls and surfaces of pelvic organs, where they grow and continue to thicken and bleed over the course of each menstrual cycle.
Going upside down, as we do in Shoulder Stand or Snail Pose or other inversions are believed to cause this retrograde movement. Not everyone agrees with this, but consensus is not always possible when we deal human beings, because we are all so variable. Inverting for you may not be a good idea.
It would be interesting to hear other yoginis thoughts, but I will leave you with one other opinion, this time from the late Esther Myers
- Start with relaxed abdominal breathing and poses like Supta Baddha Konasana (Reclined Bound Angle Pose) and Supta Virasana (Reclined Hero Pose) that gently open and stretch the abdomen and pelvis. Use these poses during times of pain, bloating, or discomfort. Then focus on seated poses that open and release the pelvis like Baddha Konasana (Bound Angle Pose) or Upavistha Konasana (Wide-Angle Seated Forward Bend). Salamba Sarvangasana (Shoulderstand) is particularly beneficial to women with endometriosis when they're not menstruating, since it helps balance the endocrine system.
- My experience with scar tissue in my abdomen from a hysterectomy is that backbends often feel wonderful at the time, but can cause cramping the next day. Start with small backbends like Bhujangasana (Cobra Pose) and Salabhasana (Locust Pose) and gradually work up to Dhanurasana (Bow Pose), Ustrasana (Camel Pose) and Urdhva Dhanurasana (Upward Bow or Wheel Pose) to see how much stretch the front body can tolerate.
- In the case of endometriosis, the key is to work gradually. Work slowly and carefully to find out what works best.
Esther's advice seems very good to me, and her choice of postures seem very Yin-like! Saddle and Straddle Pose and Butterfly. These are great ways to work the Urinary Bladder meridians. Note, however, she only recommends Shoulder Stand when you are not menstruating. In your case, you may want to eliminate the pose entirely, for a while anyway.