first off i hope your boyfriend is feeling better. i wish him a speedy recovery.
here are some thoughts off the top of my head based on the scant information you provided. i may be off base about some things because i do not have his records to review.
if kidney cancers are found early and the kidney is removed, usually the patient is cured. if the cancer has spread before it is found, removing the kidney does not prolong life span. the kidney is left in place, the oncologist will give chemotherapy and possibly radiation, and eventually the patient will die.
It is therefore vitally important to do a staging workup to find out if the cancer has spread before doing unnecessary surgery. one test to see if his doctors are competent - did they send him for a staging workup, such as a PET scan?
it is also very important to know the function of the non-cancerous kidney. if the kidney is not in good shape, such as in diabetics, dialysis will be needed.
you talked about pain. immediately following surgery, for about a week, the pain is moderate but controllable with analgesics. for the next couple of weeks the pain improves. in a month there is just a bit of soreness. i have never seen the pain you described, ever, in patients having a kidney removed.
ankle/foot swelling, called edema, can be due to things like renal failure or heart failure. Not urinating can be renal failure.
i am going to assume that they tested and found his remaining kidney to be normal before surgery, otherwise they would have told him about dialysis and you would have mentioned dialysis in your note. so BEFORE surgery his other kidney was fine. AFTER surgery he has ankle swelling and not urinating, both signs of kidney failure. My best guess is they screwed up badly and ruined his remaining kidney at surgery.
there are good surgeons, marginal surgeons, and dangerous surgeons. i could tell you stories about surgeons who are beyond incompetent. i guess any field is going to be like that. but at least if your contractor or mechanic is incompetent, all you lose is your new deck or your car.
my advice to anyone who is going to have such surgery in the future is to get a second opinion from a major university teaching hospital with a reputation for excellence. Somewhere on this message board I listed the top 10 places in the country. Certainly one of them has to be close to you.
my advice to your boyfriend is that he needs to go elsewhere to find out what they did to him, as it is unlikely they will tell him for fear of malpractice. Johns Hopkins would be an excellent choice, although anyplace on that list of 10 top places should be good. Usually it is very hard to get stubborn people to get a second opinion. Having trust in your physician when they are competent and not trying to sell you on something is fine. After a surgery that went badly, leading to complications such as you described, I am guessing his trust in his doctors is misplaced. Go see someone competent.