What you're describing is called a
pseudocyst, and it results when a fluid-filled sac forms because the catheter has slipped out of the peritoneal cavity. It will often push up against other organs. For reasons no one seems to know (or at least, that I have not found in over 15 years of research), there seems to be a greater chance of this if it has happened to you before. This is medically urgent, so please get in touch with your nsg right away.
Good luck!
LIZARD