Hello, Colonic malignancy with abdominal metastasis can cause malignant ascites. There could be a superadded bacterial infection of the peritoneum Peritonitis, which is probably what the doctors are referring to when they say that there is an infection. It could be due to many causes including any gut perforation. If so, it becomes an emergency, and surgical management is removing the malignancy and treating the peritonitis is imperative. I feel you should consult an Onchosurgeon, who would do the necessary investigations and treat the problem urgently. Hope I have answered your query. Let me know if I can assist you further. Regards, Dr. Ajit Kumar Varma