The Senior Cat - Kidney Disease
The most common type of kidney disease in cats is the chronic renal insufficiency of elderly cats. This is a slowly progressive loss of kidney function that occurs with increasing age. There is no cure and no single cause but rather the accumulation of kidney damage over a lifetime. Cats diagnosed with kidney disease can often be managed for years and experience a good quality of life.
To understand kidney disease it is first important to understand what healthy kidneys do:
- Filter waste products and toxins from the body
- Regulate electrolytes (sodium, potassium, chloride)
- Regulate Hydration
- Help regulate blood pressure
- Regulate pH balance
- Stimulate bone marrow to produce red blood cells
What happens when the kidneys don't work properly?
Renal insufficiency is a chronic, irreversible deterioration of kidney function over a period of months or years.
The kidney consists of tiny funnel-shaped tubes, called nephrons, which filter and reabsorb the fluids that balance the body.
When an individual nephron is damaged by any cause (aging, toxins, infection) it stops functioning. As more and more nephrons stop working, waste products and electrolytes can no longer be processed efficiently and more fluid remains in the urine than is reabsorbed. Cat kidneys will continue to produce urine even as the rest of the body becomes dehydrated.
What causes kidney disease?
Loss of kidney function can be caused by genetics, age, disease in other parts of the body, bacterial infection, trauma and toxins. Although kidney disease can happen at any age, chronic renal insufficiency is usually a disease of older cats.
What are the signs of kidney disease?
The first indication of kidney disease is often an increase in water consumption (polydipsia) and an increase in urine volume (polyuria).
The increased urine volume will be about double the amount produced by a healthy adult cat.
Other signs include decreased appetite, weight loss, lethargy, vomiting, nausea (licking lips), unkept coat, dry hard bowel movements, and dehydration.
In severe cases cats may develop oral sores (uremic ulcers) and very bad breath.
Subtle signs of kidney disease may be present for years (stable chronic renal insufficiency). Sudden worsening of signs (uremic crisis) can be caused by anything that alters normal pattern of eating drinking peeing and pooping. Recovery from a uremic crisis is possible. Hospitalization with intravenous catheterization and skilled nursing care is required. Remaining kidney function will be reduced and a new state of chronic insufficiency will remain to be managed. Some cats will not have sufficient kidney function remaining after a crisis to return to a stable manageable state. Rarely cats will suffer renal failure, where the kidneys shut down and produce no urine at all (anuria)
How is kidney disease diagnosed?
When signs consistent with kidney disease are noted, laboratory testing is needed to confirm and assess the severity of disfunction. A blood chemistry screen measures the amount of waste products (BUN, creatinine) and electrolytes (Na, K, Cl, Phosphorus) in the bloodstream as well as the level of dehydration (albumin, total protein). A complete blood count (CBC) can determine if there is anemia (decreased red blood cells) or possible infection (increased white blood cells). Urinalysis with culture will determine the concentration of the urine, the biochemistry of the urine and the presence of infection.
How is kidney disease treated
- Diet: A cat with kidney disease should eat a diet that provides everything a cat body needs with minimal waste that the kidneys have to process. A kidney friendly diet is one that is low in sodium and phosphorus, high in potassium, buffered to reduced acidosis, highly digestible with adequate high quality protein and calories to maintain lean body weight. Prescription diets are carefully and consistently formulated to achieve these goals. There are a few non-prescription "senior" diets that are kidney friendly. These may be appropriate for some cats with stable chronic renal insufficiency. Canned formulations provide additional water which is also important.
- Subcutaneous Fluids: It is difficult for your cat to drink enough water to keep up with the increased demand produced by inefficient kidney function. A sterile balanced electrolyte solution (lactated ringers with added potassium) administered under the skin can meet those needs. Sub-q fluids can be administered by a professional in the clinic or by you at home. The frequency of administration will depend on specific needs of each individual cat. Some cats benefit from fluids given weekly others need supplemental fluids twice daily in order to maintain hydration and stable biochemistry. Learning how to do this simple procedure gives you a tool that will improve your cat's quality of life and help you avoid emergency visits.
- Medications: Depending on related problems, such as acid stomach (nausea, poor appetite), anemia, low potassium, high phosphorus, etc. a number of medications or supplements may be prescribed. For example famotidine (Pepcid) can be given to reduce stomach acid, maripotant (Cerenia) helps with nausea, Mirtazipine is an appetite stimulant, Epogen stimulates bone marrow production of red blood cells, phosphate binders and potassium supplements may be needed especially for cats who will not eat a kidney prescription diet.
- Hospitalization and Intravenous Fluid Diuresis: Severe cases of kidney disease (uremic crisis) will need to be hospitalized for intravenous fluid therapy and supportive care. IV fluids are the quickest way to rehydrate the body and flush toxins out of the bloodstream. At this stage most cats also need medication to control nausea and vomiting as well as syringe feeding. Physical exam and laboratory values will help identify any complicating issues like pancreatitis, urinary tract infection, constipation, , oral ulcers, or anemia. Elderly cats may also have concurrent disease(s) such as hyperthyroidism, heart disease, diabetes and cancer. The length of hospital stay will vary depending on the severity of the disease and how quickly the cat responds. Three to seven days is typical.
Early intervention can keep little problems from turning into big problems!