I recently had an abscess of the abdomen after radiation also. I had a very large tumor removed from my sigmoid colon with metastasis to the overies and 2 lymph nodes. I started radiation in August of last year. I had 16 treatments and was to sick to continue. I returned to work and everything seemed to be normal. Around Christmas I noticed a swollen area in the lymph nodes on my neck. My surgeon said I was just trying to fight off a virus. Very shortly after that I noticed that my belly seemed to be swelling abnormally. I went in for a colonoscpy and petscan the next week. The colonoscpy was clear but the radiologist on duty said that he saw metabolic activity in the abdomen and the liver. He suspected that the cancer had returned and it was attached to the abdomen wall and that there was nothing that could be in done in this case. He said he wanted to do a contrast catscan to confirm. The catscan showed a large mass in the abdomen and something suspicious on the liver. The radiologist then wanted to stick a needle in my belly to check the mass. My surgeon stopped him saying that that would seed it if it were cancer. My surgeon decided to go back in the same incision and address the issue with surgery no matter what it was. It turned out to be an abscess of the abdomen. There was more than a liter of fluid involved. I looked 6 months pregnant. I am recooperating at home now and all seems well. I have asked what could have caused this and the answers I got were that they thought that I leaked in the colon area after surgery. I had a lot of cancer and was almost perferated in that area. Then there was an issue that they came up with an extra sponge on the second surgery. My surgeon says he does not think that was the issue because I would have never recooperated from the first surgery if there had been something left behind. Your story seems to make a lot of sense to me. I am going to speak with my surgeon about this issue. Thanks so much for sharing.