Any tissue damage will cause some “free” fluid. Bleeding or just the body’s response to damage, I think. I have watched free fluid from large bruises travel down my leg. “Peritoneal fluid” seems like an odd term to use. It implies another hernia or a breach of the peritoneum. I’m not a doctor.
It looks like they’re just saying that they saw some fluid that shouldn’t be there but it’s not clear where it came from.
“anterior to the common femoral vessels at the prior hernia repair” means the fluid was in front of the femoral vessels. The mesh is placed behind the femoral vessels, so that means the fluid was between the mesh and the abdominal wall. Which implies that the mesh might have torn free from the abdominal wall and there is a damaged spot. Again, I’m not a doctor of medicine, but in view of how the mesh is supposed to work, the simple fix would be to get it to reattach itself. But, in the big picture, if that is the case, the question is “why did it break free?”
Anyway, it’s good to collect lots of information before making a decision. Good luck.