Symptoms of renal failure in dogs include vomiting, lethargy, diarrhea, constipation, weight loss, increased thirst and acute blindness. Other symptoms include blood in the urine and an increase in the frequency of urination as well as the amount of urine that is produced, lack of appetite leading to anorexia, seizures and coma. All dogs may not experience the same symptoms, and those that manifest typically do so gradually over time.
The symptoms seen in dogs due to renal failure are typically caused by a condition known as uremia. Uremia occurs as kidney function declines, leading to the retention of ammonia, nitrogen, acids and other harmful waste products in the dog's blood and tissue. In general, dogs do not show symptoms of renal failure until they lose approximately 75 percent of their functioning kidney tissue after uremia sets in. This means that a great deal of damage has already taken place before any signs or symptoms are noticed.
The loss of kidney tissue that results in renal failure is often caused by a kidney stone that completely obstructs the urinary tract, the rupture of the bladder or urethra, inadequate blood flow to the kidneys which leads to shock, or congestive heart failure resulting in low blood pressure and reduced blood flow to the kidneys. Some other causes include poisoning from antifreeze or other harmful substances, lyme disease and leptospirosis.