Hello, Erika. I packed as if I were heading to the deepest jungles in the remotest parts of the planet. Which was silly, but it was nerves. Here is what I did end up using, and I learned to do better for the reversal packing.
Long-sleeved cotton t shirt to wear under the hospital gown because hospital rooms can be very cold at 1:30am and there are no maintenance staff to turn up the room's heat. You can ask the nurse for a heated blanket too, if available. Socks to wear in bed. I didn't bother bringing PJs because hospital gowns work best when doctors, nurses and residents examine the bag, wound, and stoma many times a day.
Rubber slippers to wear in your room and into the shower. I brought along good supportive ones (not cheap beach flip flops) to help me when walking the halls after surgery. They went into the laundry when I got home.
Facecloth, because hospital wash-cloths are like sandpaper after being bleached 1,000 times. Toothbrush and cup, and mouthwash. Soap or cleanser in lotion form is easier to handle; you won't be able to bend over to pick up dropped bar soap in the hospital shower, don't ask how I know this. Travel sized shampoo. Face moisturizer or tiny pot of Vaseline because skin will dry out, I don't know why. Everything should be travel size.
Ipad and charger to keep connected. Or not. My hospital roommate was on her cellphone all the time, she was very loud. I rented a hospital TV and it came with earplugs. One book to read, although to be honest, I was so exhausted I didn't read a lot. Any medication you usually take. Eyeglasses (name and phone number inside the case) and contact lens and solution.
Unbreakable water bottle. I kept mine within reach. Stay hydrated. They might give you ice chips at first.
I wore the same outfit to and from hospital: loose, pull on clothes, not jeans. When you leave hospital you'll have an external bag and some discomfort to deal with so loose pull on pants will be so comfortable. Shoes or boots you can just step in to. I fit everything into a large tote bag.
Try not to worry. Trust your surgeon. Make a list of questions to ask at your pre-admission meeting where they give you instructions. Will you have an epidural? I did and it helped manage pain, along with morphine. When they give you the anaesthesia just relax and know that when you wake up you will be disease free and have a new life. And we'll be here to help then too.