I can only relate it to humans right now
It usually mens reducing salt, potassium and such. Also low protein and high carbohydrate. And we usually only give as much fluid as is measured out.......Which is difficult in dogs. It also depends on what type/level of kidney failure. Is it where they are thinking they have to use dialysis or just the renal function test is somewhat out of wack. In humans if it is just a slight change in renal function tests, the diet doesn't change much at all
Human version copied.......
"Protein: You will need to limit the amount of protein in your diet. This will help decrease the wastes in your blood, helping your kidneys to work better. Foods that are high in protein are meat, poultry (chicken), fish, eggs, and dairy products (milk, cheese, yogurt). Your caregiver will tell you how much protein to eat each day.
Phosphorus: You will need to limit the amount of phosphorus in your diet. When you have kidney failure, your kidneys cannot get rid of extra phosphorus that builds up in your blood. This may cause calcium to leave your bones and make them weak. Foods that are high in phosphorus are dairy products, beans, peas and nuts. It is also found in liquids such as cocoa, beer and cola drinks. Your caregiver will tell you how much phosphorus you should have in your diet each day.
Sodium: You may have to limit the amount of sodium in your diet if you have certain health problems. These may include high blood pressure or extra fluid in your body. Your caregiver will tell you how much sodium you should have each day. Table salt, canned foods, processed meats like deli meats and sausage, soups and salted snacks are high in sodium. You may have to limit high sodium foods and table salt in your diet.
Potassium: Usually, you do not need to limit the amount of potassium in your diet. However, you may need to limit potassium if you have too much potassium in your blood. Your caregiver will tell you if your blood levels of potassium are too high. Potassium is found in fruits and vegetables. You may have to limit fruits and vegetables that are high in potassium."
It would be quite difficult if this a serious renal failure. Food that would be alright: fruits, grains, and vegetables. These foods provide energy, as well as fiber, minerals, and vitamins.
CAnned fish is actually one on top of the list to stop...Phosphorus and sodium being the big uglies there.
Like I said I am only relating back to human kidney failure
) I did see green tripe sugggested on there for a kidney diet, and there are discussions on why being on raw is not too much protein. 
