Hello My 10 Year Old Daughter Has Fluid Showing In

Hello my 10 year old daughter has fluid showing in scan between bowel and rectum ( pouch ) . She has been in pain for weeks , nauseous and not eating .
We don't know how significant this is ? She is in antibiotics for 3 weeks to see if improves but is in so much pain and can't walk very well .
Any ideas please ?
Thanks