I spayed an older dog the other day. The owner reported no known issues but during surgery her left ovary happened to be the size of a small orange. After surgery I cut it open and found it to be full of cysts. I have no idea if this was bothering the dog or not but I'd hate to think that if it does and we don't know about it there could be a bunch of intact dogs walking around with painful ovaries. I have seen this condition in both dogs and cats but this is the most extreme example I have found. This dog was only 22 lbs by the way.