Small Intestine Cancer

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My mom was diagnosed with small intestine cancer, she had a tumor and lives far from me so my sister and we went there for the surgery and after a 4 hour surgery the doctor came out and told us that it is stage 3 and in her lymph we are so upset with this news. My mom came home after 5 days in the hospital and was home 2 hours and could not breath so we called 911 and they admitted her for 2 more days in a different hospital, so then they released her again this time with oxygen and meds for infection she was fine then my sister and I had to get home to our kids and we flew home the next day. I called my mom so many times and later that night she said she was bleeding from her rectum and I said call the home nurse and they told her it was fine and wait so my mom waited and waited until she was bleeding chucks out so her sister rushed over there and rushed her back to the hospital and now is in ICU and had a blood transfusion what a night mare she is very weak. I really need to understand this the one doctor said the blood can be from the surgery from cutting part of the small intestine and putting it back together but how is that possible I would think she would be bleeding from day one not over a week later. Please advise me and can she survive small intestine stage 3 cancer:(