Surprise cyst found

Hi, im a male age 44 in overall good health. I went in for an ultrasound because I was having gallbladder symptoms in my right side. My doctor called me today and told me they found a cyst on my left kidney. He said it was small and was 'between simple & complex". I understand the difference between the two separately but what does it mean when it's "in between"? I wanted to ask my doc that directly but he wasn't available and now I'm a little worried. Any thoughts would be appreciated.

[Paderla Anitha, DNB]

Hello and hope you are doing well.

Simple cysts usually have fluid and are uniform. Complex cysts may have echogenic  shadows and may have a thickened wall. The cysts identified could have a combination of free fluid and some ill defined echogenic shadows.

Hope this helped and do keep us posted.