What does "heterogenously echogenic lesion within left ovary" mean? also says "mild heterogeneous posterior acoustic shadowing".

Indeterminate lesion: By far the most common cystic ovarian lesions are benign functional ovarian cysts. When a lesion doesn't follow a typical benign imaging characteristics (heterogenous or shadowing) on ultrasound, it requires either follow up to resolution and/or further evaluation including MRI in some instances. Without actually seeing the images, it's hard to make any further recommendations. Hope this helps.