Not a problem on modern ships. Most have disabled cabins which have wider doors and more room for wheelchairs but these get booked up early.
Cruised through the panama canal on the arcadia in march, my husband was in a wheelchair throughout the cruise and the staff couldnt have done enough for him. everyone was so helpful, even going aboard the tender to a couple of the islands wasnt a problem. dont let being wheelchair bound put you off cruising, it also has its advantages.