Kidney (Renal Failure)

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Kidney (Renal Failure)

The body has two kidneys (a right and a left) that are located on either side of the spine around the area of the last rib. The kidneys are responsible for filtering and eliminating waste products from the body through the formation of urine. They are also responsible for regulating electrolyte, water, and the acid-base content of the blood. They also produce a hormone called erythropoietin that stimulates red blood cell formation. The kidneys' ability to perform these functions is partially determined by the flow of blood to the kidney. When this blood flow is impaired, kidney disease, and ultimately kidney failure, can result.

Kidney failure can occur in one of two forms - acute (sudden) or chronic (having built up over time). These two forms of kidney failure present differently and so will be handled completely separate.

Acute Renal Failure (ARF)

ARF can be caused by sudden decreases in blood flow such as from trauma, shock, deep anesthesia, hyperthermia or hypothermia. Toxins/drugs are another major cause of ARF. Ethylene glycol (antifreeze), gentamicin, Amphotericin B, lead, cisplatin are examples of medications/toxins that cause ARF. Other diseases such as those causing high calcium (i.e. cancer) or impairing heart function can cause ARF. Finally, infections of the kidneys and immune- mediated diseases targeted at the kidneys are other causes.

Signs of ARF include inappetance, vomiting, lethargy, and diarrhea. Animals with ARF are often dehydrated, have pale mucous membranes, may have large painful kidneys, and have decreased urine output.

A diagnosis is made with blood tests to check for elevations in BUN and creatinine (breakdown products of proteins that are excreted by the kidney), in conjunction with dilute urine (a result obtained with a urinalysis). Complete blood work is important to check for electrolyte abnormalities and concurrent disease states. A urinalysis is important to check for signs of infection, underlying disease processes, as well as to get the concentration of the urine. An x-ray or ultrasound of the abdomen may be warranted to better characterize the disease.

Treatment for ARF involves correcting the underlying problem. This may involve antibiotics or discontinuing a medication. Performing a kidney biopsy can help determine a definitive underlying cause. Many times an underlying cause cannot be determined. Supportive treatment involves intravenous fluids, correcting electrolyte abnormalities, controlling vomiting, and restoring urine output. This involves hospitalization, 24- hour care and even dialysis.

Prognosis depends upon the degree of urine output, the underlying cause, presence of other disease states, timing of diagnosis and onset of treatment and response to initial therapy.

Chronic Renal (kidney) Failure (CRF)

CRF is the most common kidney disorder in dogs and cats. It is associated with irreversible structural damage within the kidney. The damage can be hidden for months but is usually progressive. It is more common in older animals but can happen at any age (mean age in dogs is 6.5 -7 years and 7.4 years in cats). The underlying cause is often undetermined and not present at the time of diagnosis. Causes include ARF (long-term damage leads to CRF), infections, cancer, urinary tract obstructions, congenital diseases, and familial (inherited) diseases. Familial disease occurs in Norwegian Elkhounds, Lhasa apso, Shih Tzus, Samoyeds, Standard Poodles, Shar-peis, Basenjis, Beagles, Chow Chows, Golden Retrievers, Doberman Pinschers, and Schnauzers. For cats - Maine coons, Abyssinians, Siamese, Russian blues, and Burmese have familial kidney disease. Persians are prone to a kidney disease known as polycystic kidney disease.

A CRF patient may drink and urinate often, have weight loss, inappetance, lethargy, vomiting, diarrhea, and weakness. They are often dehydrated, may have pale mucous membranes, high blood pressure, small, irregular kidneys and have oral ulcers.

Diagnosis is based on blood work (a CBC and chemistry panel) and urinalysis. A CRF animal, like an ARF animal, will have an elevated BUN and creatinine and dilute urine. Other abnormalities may include anemia, electrolyte imbalances (most notably elevated phosphorous), and calcium abnormalities.

Treatment involves subcutaneous (under the skin) fluids or IV fluid to correct dehydration and keep the kidney's blood flow adequate. The electrolyte abnormalities need to be corrected. If elevated phosphorous is present, a medication like Amphogel® or Basalgel® may be used. A medication may be prescribed to combat ulcers, prevent vomiting, treat high blood pressure, and a transfusion may even be necessary in severely anemic animals. A hormone, erythropoietin, may also be prescribed to treat the anemia. A kidney transplant can be performed in cats if they meet certain criteria. Kidney transplants are currently being done ate the University of California, Davis and the University of Wisconsin, Madison. The University of Guelph in Ontario, Canada has researchers working on kidney transplants in dogs, but they have met with limited success.

The long-term prognosis for CRF is poor since it is an irreversible disease, but the progression can be slowed with proper treatment.