Dogs bodies, like humans, suffer over time and their kidneys are the first organ to wear out . The kidney starts to lose its function over time and next to arthritis and cancer, kidney failure is the leading cause of illness in older dogs.
What do the kidneys actually do anyway?
Kidneys keep the dog's body free of the wastes that accumulate during metabolism. The removal of wastes occurs in little systems within the kidneys called nephrons. Each nephron contains a small filtering structure called a glomerulus. The glomerulus keep normal blood proteins and cells in the bloodstream, while allowing extra fluid and wastes to pass through to end up in the dog's urine. A
chemical exchange takes place, as waste materials and water leave the blood and enter the urinary system. The kidneys also regulate the body’s acidity and, through regulation of body salt content, they help control the dog's blood pressure.
The cells associated with nephrons produce a hormone called erythropoietin and an enzyme called renin. Erythropoietin is needed for the dog's body to produce and maintain red blood cells while renin activates another hormone called angiotensin which helps control blood pressure. Kidneys are required to process vitamin D into calcitriol which preserves calcium for bones.
In kidney disease the glomerulus are damaged, lost, or blocked with proteins and inflammatory cells. Without the glomerulus functioning properly, then the kidney processing will not be completed, hence complications to this organ.
Why the dog starts urinating.....a lot!
When the dog's body senses something is not working or functioning at its full capacity, it will then attempt to keep the body waste-free, working the dog's kidney's overtime, using their small remaining capacity to remove waste. This is why dog's have an insatiable need for thirst followed by a huge amount of urination. For a while, this compensation keeps it’s body clean enough of wastes to function, but gradually, the dog can not consume enough water to keep waste levels in check. By the time the dog experiences weight loss, anemia, and abnormal blood work results, over half of its kidney glomeruli have been lost, which cannot be replaced.
The signs start to show
The first sign that there is a problem with the kidney's is when the dog begins to drink water and urinate excessively. This can go unnoticed for some time and it's when the owner notices the dog is losing weight, not interested in food, no energy, sleeps more than usual and has a dull coat that the dog will come into the clinic.
In advanced kidney disease, dogs will no longer eat. They often have digestive disturbances such as nausea, retching and diarrhea. Their water intake decreases and they become dehydrated.
Why does this happen?
Nothing lasts forever and every organism has its weakest link. Cells of the kidney cannot replace or regenerate themselves as they do in the liver, lungs, bone and skin. Once a glomerulus ages and is lost, it is lost forever. This is probably the most common cause of kidney failure in dogs.
Which tests will be performed?
As kidneys scar, they become hardened, small and lumpy. In these cases, the vet will run tests that specifically target this organ. The tests include:
Urine Specific Gravity (USG)
USG determines how concentrated the urine is. Dogs that have compromised kidneys cannot produce concentrated urine. The lower the specific gravity, the more serious the kidney problem is.
Blood Urea Nitrogen (BUN)
Blood Urea Nitrogen, a waste product of metabolism, rises in the blood of dogs with failing kidneys. BUN levels in the blood of sick dogs begins to rise when not enough healthy kidney tissue remains to excrete it into the dog’s urine. The higher its level in the blood - the more serious the kidney problem is likely to be.
Creatinine is a protein that tends to rise and fall in tandem with BUN. Creatinine-determination is a more sensitive test for kidney disease then BUN-determination because blood levels of creatinine fluctuate less than urea nitrogen in response to a dogs being dehydrated or consuming a high-protein meal. So BUN and Creatinine tests are always run together.
Phosphorus and Calcium
Phosphorus is one of the mineral constituents of blood. Compromised kidneys have difficulty excreting sufficient phosphorus into the urine and an elevated phosphorus reading is another sign of kidney failure. As the ratio of phosphorus to calcium in the blood becomes abnormal, the dogs bones will weaken.
When a dog's kidneys start to fail, its body potassium levels will rise. This can cause fatigue, nausea and an irregular, slow heartbeat.
Packed Cell Volume (PCV)
Packed Cell Volume is measured for anemia. When a dog with kidney failure has a PCV that is low, it is not manufacturing sufficient red blood cells. One of the hormones involved in red blood cell manufacture is produced in the kidneys called erythropoetin. When the dog's kidneys start to deteriorate, not enough of this hormone is produced.
It is common for dogs with chronic kidney disease to have high blood pressure. It is unclear if the high blood pressure is part of the cause of kidney damage, or the result of kidney damage. High blood pressure is known to damage the kidneys – but kidney disease is also known to elevate blood pressure.
You can't prevent kidney disease, but careful observation can make that trip to the vet come sooner rather than later.