One year after colon cancer surgery, there is fluid accumulation in the pelvis, considering inflammation, tumor recurrence and metastasis, etc. It is necessary to go to the hospital in time to do examination, clarify the cause of the disease and then actively treat it. 1. Inflammation: when pathogenic bacteria infection occurs, inflammation will cause pelvic mucosa to ooze and form effusion. It is recommended to use antibiotics such as metronidazole, levofloxacin, doxycycline and other drugs to control the infection and reduce the formation of pelvic effusion. The drugs should be used according to the doctor’s instruction, and the patients who have adverse reactions should consult the doctor in time, and those who are allergic to the drugs are forbidden to use them. 2. Tumor recurrence and metastasis: one year after colon cancer surgery, when tumor cells metastasize and colonize the pelvis, pelvic effusion may be caused, and the prognosis of the disease can be improved through radiotherapy, chemotherapy, targeted therapy and other comprehensive treatments to improve the clinical symptoms. After surgery, colon cancer patients should go to the hospital for regular rechecking, and if they find effusion or other discomforts, they should consult the doctor immediately, and actively cooperate with the doctor to receive standardized treatment after the cause of the disease is clarified.