Docs can you explain what is a "subcapsular cyst" and a "parenchymal cyst" on a human kidney?

Fluid sac: A cyst is a fluid filled sac anywhere in the body. They are benign. Sub capsular means under the kidney capsule (surface). Parenchyma means in the kidney substance. They may be very small-finger tip sized, or can be as large as the whole kidney. They may enlarge with time. Generally they don't cause symptoms but should be followed over the years due to small risk of cancer or kidney injury.