I don't THINK that it has anything to do with the peritonitis? What's the story on your appendix?
But that's only a guess, ANY organ that leaks into the peritoneal cavity can cause peritonitis but the majority are caused by a burst appendix...or in the inner cities, a gunshot or knife wound.
If it's confirmed as an HA, my guess is that it will be YOUR call...the risk of keeping it is small, maybe smaller than the risk of removal.
The only thing that MUST be removed is a malignancy.
Let's see what the MRI shows. I'm still betting on a harmless hemangioma