Why Is Flagyl Prescribed?

Hi, my mother has been placed on Flagyl 500mg three times daily for 2 weeks, and Ciprofloxacin HCL 500 mg one tab twice daily for 14 days following an emergency colectomy for intussisception due to a cancerous tumor. She also had a drain placed in her abdomen one week post surgery due to an abcess. She says the Flagyl upsets her stomach terribly. Her hemoglobin is low also at 7.8, an increase of post surgery hemoglobin of 7. My question is why would she need to be taking the Flagyl; they never said she had cdiff. And it is so hard to get her to eat much, so it seems to be countering everything we re trying to do for her nutritionally. She s supposed to be taking iron, but with her stomach already so upset from all the meds, Tylenol and Ibuprofen also, she is hesitant to take it. Her hands and wrists are also swollen, as are her feet. I imagine the removal of lymph nodes in her abdomen has an effect on her swelling feet? Are the medications causing her to swell? She was up with terrible pain upon urination last night. They did a urinalysis the day of discharge, and were going to culture it also. She was discharged yesterday.