I wanted to clarify my statement above...
My surgeon, from the first surgery until about 10 weeks after the third, had me on the "nothing heavier than a milk jug" restriction. When I had a followup 10 weeks out, he cleared me to resume exercise, including weight training without restrictions, other than if something hurts, stop doing it, and to avoid weight that puts a heavy strain on the anal sphincters for the time being. All that seemed reasonable.
For me personally, my goal isn't to get big or "swole," but to be in the best shape as I can be in. I never again want to feel as weak as I felt after the emergency surgery last year.
So, I'm doing a lot of high intensity cardio and high rep/lower weight lifting some days, and body weight exercises with more moderate cardio on other days. All days, I focus on core strength, with the rationale that slowly increasing strength in that area after being opened from sternum to groin three times in a year is only a good thing.
I've seen no ill effects from the weight training, and I'm probably at about the same general strength level as prior to the first surgery now. I also feel significantly better, and the days I go to the gym see better pouch function than the days I skip working out.
But everyone is different. Someone who was conditioned to heavy/power lifting prior to surgery is probably in a better place to get back to that kind of exercise than someone, like me, who was never there in the first place.
I'm cautious about how much weight I work with, not only for the pouch, but because mid-40s muscles don't heal the way mid-20s muscles do, and after almost 4 months of regular exercise, I'm in far better physical condition than I was before my first and only UC flair and surgery last year.
I think, basically, if something hurts beyond normal exercise fatigue/soreness, or if you're feeling stresses in the anal or abdominal region, stop what you're doing and talk to a doctor to see if it's okay or if there's a better way.
I'm looking forward to getting cleared to do more work that is off limits to me now (particularly squats and the like that are off limits now), but for me, in consultation with my doctor, what I'm doing seems to be working.
Hell, I even have visible abs these days, and that hasn't been the case in a long, long time.