Hi. Sorry to hear about your back pain from a cyst. Ugh, as if it isn't hard enough being a woman, right? So, the adnexa is actually an area of the body. It includes fallopian tubes, ovaries, uterus, and the connecting tissues. Who knew that had it's own name as a region? I just called it my reproductive tract but adnexa is the proper term. So an adnexal cyst is in that region. Septated means it has separate chambers to the cyst. Septa is walls, and septated cysts also usually have thick walls. It may be partially solid or filled with fluid. They are common in women of child bearing age. Adnexal cysts are usually filled with fluid and your doctor may be taking a wait and see approach because they most often go away on their own without treatment. You do not mention your age by the way. If you are over 40, they will watch the cyst more carefully. Back pain is a symptom of this type of cyst and the position of it that is common. There are others you could have, so I'm glad at least you don't have some of the other things that you could be experiencing. Believe it or not, yours is not at the size yet that they consider large. 8 to 10 cm is when they consider more aggressive approaches to removing it such as laparoscopic surgery. I had a cyst like this in my 30's and it passed naturally. It was like a very uncomfortable, bad period (happened at time of period) with bad cramps and extra bleeding. I have not had one since. Here is some info on it https://www.doctorshealthpress.com/womens-health/adnexal-cyst-and-mass-symptoms-causes-diagnosis-and-treatment/
What is your doctors suggestion for it?