Your cat’s kidneys function primarily in removing waste products from the blood, maintaining hydration, and producing urine. Chronic Renal Failure (CRF) is not evident until approximately 70% of kidney tissue is destroyed. The kidneys are able to compensate for degeneration of tissue up to this point by excreting waste products at a lower concentration over a larger volume. At 70% loss of function, the kidneys are no longer able to filter waste products from the blood and they begin to accumulate in the blood stream. The sudden onset of severe disease is often apparent at this point. Symptoms of CRF include weight loss, poor coat quality, dehydration, bad breath, lethargy, depression, increased drinking and urination, vomiting and diarrhea.
CRF is most commonly seen in older cats. Only about 10% of cases occur in cats less than three years old. A number of different diseases can eventually lead to CRF. These diseases include: congenital malformation of the kidneys (Polycystic kidneys), bacterial kidney infection (Pyelonephritis), cancer (Neoplasia), a buildup of unusual protein in the kidneys (Amyloidosis), damage to the filtration membrane of the kidneys (Glomerulonephritis), and viral infections (FeLV or FIP).
Diagnosis of CRF is most often made using blood work, urinalysis, palpation and occasional a radiograph. Complete blood work is the most accurate way to diagnose renal disease. Blood work allows us to detect increased levels of two waste products in the blood stream- blood urea nitrogen (BUN) and creatinine. Increases in either of these waste products indicate that the kidneys are not functioning properly. Examining the specific gravity of a urine sample allows us to determine if the kidneys are able to properly concentrate urine. It also allows us to detect possible infection. Very clear, dilute urine is an indication that the kidneys are no longer functioning correctly. Severely diseased kidneys often shrink and become “lumpy”. Your veterinarian will sometimes be able to feel these diseased kidneys during an examination. Although radiographs are not commonly used as a tool for diagnosing CRF, they are important in ruling out unrelated causes of disease. It is also possible to see severely diseased kidneys in an x-ray.
The most common treatment for CRF involves fluid therapy. The best way to flush toxins from the blood stream is to administer intravenous fluids through a catheter placed in a front leg until the BUN returns to normal. This requires hospitalization for 3+ days and repeated blood work. Fluids can also be administered at home under the skin (subcutaneously) twice daily. Encouraging your cat to take in as much water as possible is very important as cats with renal failure can dehydrate rapidly. Feeding canned food and using a water fountain help to ensure that your cat is taking in as much fluid as possible. 70% of all cats with fountains drink more water.
Feeding a diet low in protein and low in phosphorus can keep the level of waste products in the blood stream at a minimum. Changing to an appropriate diet before symptoms appear can extend the life of your pet by 600 days. Hills Prescription diets k/d and a/d, Purina NF, and Royal Canin LP are all appropriate options. Canned and dry forms are available. Additionally, cats in renal failure tend to excrete too much potassium in their urine. Supplementing with a flavored gel called Tumil-K can help restore some potassium to your cat’s system. Many cats in renal failure experience vomiting, anemia (a decrease in red blood cells) and high blood pressure. These symptoms can often be alleviated with appropriate medications.
Another common ailment of the older cat is hyperthyroidism. Unfortunately, the treatment of hyperthyroidism can cause underlying CRF to become more obvious. Hyperthyroidism causes increased blood flow to the kidneys, increasing filtration and decreasing the buildup of toxins in the bloodstream. The treatment of hyperthyroidism and the return to normal blood flow through the kidneys can cause BUN and creatinine to accumulate in the blood at an increased rate.
Unfortunately, once the kidneys are damaged they have limited ability to recover. Most cases of CRF progress very slowly, and with early detection and treatment your cat may have several years of quality life ahead.