First, get the whole detailed story from your healthcare professionals. Make them explain, to your satisfaction, exactly what -must- be done and -why-. If they don't or can't make it all understandable and justifiable, then ask other healthcare professionals. I wouldn't let anyone do anything to me, especially anything radical or life-changing, without feeling it was the right plan for me.
I was diagnosed T3 N0 M0 (or MX, no known metastases) and the tumor took up most of my rectum. It was low enough to be -very- close to my anus. The game plan developed by my team was neoadjuvant (pre-surgery) chemo and radiation, then about 6 weeks later, surgical removal of the tumor and resection (reconnection) of the remaining colon to my anus. To let all of that heal, feces has been rerouted through a loop ileostomy (a temporary colostomy). I am now awaiting a leak test of my patched colon and the take down or reversal of the ileostomy to make use of my colon again.
Prior to surgery, I actually had a heart to heart with my surgeon and asked him not to leave me with a permanent colostomy, no matter what he found. He said he could not make that promise. He said he would have tissue from my anus tested, while I was on the table, and if it was cancerous, he would remove it. He said he would not knowingly leave cancer in my body as I am -only- 49 years old and too young to want that sort of option... choosing death over my perception of quality of life being destroyed.
So, when I went into surgery, I didn't know what I'd wake up with... or without. I thought a lot about that and the bottom line is, I want to live.
The truth is, people live full and happy lives with permanent colostomies. A pouch on your tummy does not define you. Other people don't even know it's there unless you tell them. There's a little inconvenience to it, but there's inconvenience in having to hunt for a restroom, stock toilet paper, wipe your own butt, etc... when you go like other people do. This is just a bit different.
Even though I am only temporarily 'bagged', it has become a sort of natural part of my life. I could see how you could get used to it and just carry on. Sure no one would choose it, but it's easy enough to live with. It also beats the heck out of dying some grueling death, or in fact dying at all.
If a pouch seems like a hardship, imagine the tortures of the damned from a colon being eaten or blocked by cancer, a cancer which would surely spread to other parts of your body if left unchecked and causing havoc there too. That would be a seriously evil choice.
I didn't really trust all of that before my surgery and living with an ostomy, but I get it now and it's okay. If my future ultimately includes a permanent colostomy, then I know I can live with that. I want a future, period.