I'm 11 days post op and behind what I can eat. I haven't eaten in 2 days cuz I've been severely dehydrated so I been drinking as much water and powerade zero as possible so I have no room for broth or anything.... I stepped on the scale and I'm up 4 pounds from yesterday how does this happen any advice?!!

Bodies are weird and wonky things. As are scales. Could be anything from water weight to time of the month (no idea of your gender, sorry) to needing to poop to just weird fluctuations with no real reason. Don't get concerned unless it's a long time trend. And believe me, your body will continue to do weird things. If it's going to stress you out, weight less frequently or use a site like trendweight.com so that you focus on the big picture rather than day-to-day fluctuations. I promise you you haven't gained four lbs of fat though!

Thank you for ur advice

Keep sipping. Frankly, until you can get all of your fluids and protein you need to stay off the scale.