What Can Cause Hypo Density In The Region Of Left Ovary?

Hi - I have a question about ovaries. I had my uterus & right ovary removed. Then in 2008 I had my left ovary removed - or so I thought. I have been having pain and had a ct scan done last week. The report states that I have a 12-22mm hypodensity in the region of the left ovary and that it may represent a small remaining ovary. How can this happen and if i still have a portion of an ovary has it still been producing hormones and could that have made my endometrosis grow? thanks