Kidney failure occurs when more than three quarters of kidney function has been lost. This may happen quickly, "acute" kidney failure, or slowly. "chronic" kidney failure . Causes may be genetic, acquired through injury, infection, poisoning, diet or metabolic disorder, or in the case of chronic kidney failure, be age-related. Treatments vary according to the specific cause. Because pets now live so long many eventually develop an age-related decline in kidney function, chronic kidney failure,
Acute Kidney Failure
Sudden interruption of efficient renal filtration causes acute kidney failure. While local infection directly damages the kidneys, most instances of kidney failure occur as a result of events outside the kidneys, such as shock or systemic disease, that have a devastating secondary effect on renal filtration. Causes include:
Lower urinary tract infection that moves up the system into the kidneys, causing a purulent infection in the filtering nephrons, a pyelonephritis.
Leptospirosis in dogs
Burns, trauma, hemorrhage, heat stroke, urinary tract obstruction
Low blood pressure, blood clots
Generalised (Systemic) Disease
Liver failure, peritonitis, pancreatitis
Tumours, chemicals such as ethylene glycol antifreeze are toxic to the kidneys. In some pets with low blood pressure non steroid anti inflammatory drugs (NSAIDs) can cause acute kidney failure.
Signs Of Acute Kidney Failure
Signs include loss of appetite, vomiting, diarrhea, lethargy and weakness. Because there are so many underlying causes of acute kidney failure, these signs are mixed with those of the triggering condition. Acute kidney failure occurs suddenly. There is seldom any weight loss or change in the hair or coat. Pets are however dehydrated. Temperature is often below normal (hypothermia). There may be ulcers in the mouth and a typically sweet (uremic) smell to the pet's breath. The whites of the eyes (sclera) may be bloodshot. Pets with acute kidney failure breath faster and have faster heart rates than normal.
The initial aim of our treatment is to sustain life and eliminate the cause of kidney failure. Intravenous fluid therapy is vital. The aim of fluid therapy is to replace fluid losses, maintain good fluid balance and promote urine formation. We only start to relax when the patient urinates. Diuretics such as frusemide are excellent when used early in acute renal failure. At the same time the underlying condition is treated, for example, antibiotics for pyelonephritis. Mouth damage caused by uremia (ulcers, stomatitis) is treated with chlorhexidine mouth wash several times daily. Nausea is controlled with metoclopramide. Most pets are unwilling or unable to eat so nourishment is added to the intravenous drip. Food is given by stomach tube if there is no vomiting.
The prognosis depends on the cause of renal failure and the aggressiveness and efficiency of treatment.
Uraemia is the term used to describe the signs that develop when a pet has kidney failure. Technically, it refers to the build-up of waste products such as ammonia and acetoacetic acid in the body. The presence of these chemicals produces a distinctive "uremic" smell. Typical signs of uraemia include:
- Excess thirst and drinking
- Loss of appetite
- Loss of weight
- Lethargy and/or apathy
- Ammonia breath
- Pale gums and mouth ulcers
- Vomiting and/or diarrhea
Chronic Kidney Failure
While chronic renal failure develops insidiously, invariably it concludes with all the signs of uremia. As chronic renal failure develops a pet loses first body fat, then muscle mass. The coat sheds more, loses its sheen and looks unkempt. There is a general slowing down, fatigue, increasing listlessness and a loss of interest in the surroundings. Mild retching begins, followed by vomiting froth or meals. Body tremors or loss of fine balance develop. Eventually mild seizures occur.
In cats we often feel small, shrunken kidneys, hear a slight hear murmur and scent the faintest uremic small to the breath. The gums look drier than normal. Blood chemistry tests show elevated blood urea nitrogen and creatinine. Blood phosphorus levels rise. Anemia often develops. Blood pressure also inevitably rises.
Diet management is the primary treatment for chronic renal failure. The objectives of the diet are:
- Reduce phosphorus to slow the progression of kidney failure. (Reducing protein alone, without reducing phosphorus does not slow the progression of chronic renal failure.)
- Reduce sodium to limit hypertension.
- Increase B vitamins that are increasingly lost through renal failure.
- Increase fat to increase calorie concentration.
- Increase omega 3 fatty acids, to protect kidney function.
- Fluid are sometimes given intravenously or, in certain circumstances, under the skin (subcutaneously).
- High blood pressure is managed with ACE inhibitors such as enalapril or calcium-channel blockers such as amlodipine besylate.
Because many drugs are cleared from the body by the kidneys, the dose of all drugs a pet is receiving should be reevaluated.
Ashley McManus will advise you on the best diet for your pet.