Chronic Renal Disease (CRD) In Cats
The kidneys have many important functions, including:
• Filtering of blood to remove toxins
• Water balance/maintaining appropriate hydration
• Maintaining appropriate electrolyte levels
• Making erythropoietin, the hormone that stimulates red blood cell production
• Helps control blood pressure
For most types of kidney disease seen in cats, excessive drinking and urination is the first sign noticed by owners. This occurs because the kidneys can no longer maintain the water balance and water is spilled into the urine in large amounts. Owners may also notice weight loss or anorexia; however, a large number of cats are diagnosed with kidney disease by blood work and urinalysis before they start showing any clinical signs.
Causes of CRF
Kidney disease can have many causes and can be diagnosed with routine blood and urine tests. It is important to determine the underlying cause of kidney disease as this can affect treatment and prognosis. The doctor may recommend radiographs, an ultrasound, and/or a urine culture to help determine the cause of the kidney disease. Some common causes of kidney failure include:
• Chronic inflammation that leads to scarring: the most common cause of kidney disease in older cats
• Genetics: Abyssinian and Persian cats have an inherited form
• Infection: Bacterial, FIP, FIV, FeLV
• Stones: blocking the flow of urine from the kidney, if left untreated can cause permanent damage to the kidneys
• Toxins: including antifreeze and acetaminophen
• Cancer: lymphoma, other cancers
The most common symptoms seen in cats with chronic renal disease is increased urination and increased thirst. You may also notice vomiting, constipation, decreased or lack of appetite, weight loss, urinating outside the box, lethargy, or urine leakage. Most cats are found to have chronic kidney disease on routine blood tests before they show any signs of illness at home. Early detection is beneficial for cats so we can start managing the kidney disease before they become sick and hopefully avoiding hospitalizations.
Because of kidneys’ numerous functions, there are many potential changes that may be found on blood work and urinalysis. The most common ones include:
• Elevated Blood Urea Nitrogen (BUN) and creatinine (azotemia): these represent toxins accumulating in the blood; these substances can cause nausea, vomiting, inappetance, and other problems
• Decreased potassium (hypokalemia): can cause weakness, vomiting, and inappetance and, in extreme cases, arrhythmias and death; ventroflexion of the neck (chin flexed towards neck) is a classic sign of hypokalemia
• Elevated phosphorous (hyperphosphotemia): can cause mineralization of tissues, inappetance, and other problems
• Decreased red blood cell count (anemia): caused by a lack of erythropoietin; anemia causes weakness and lethargy and, in extreme cases, death.
• Decreased urine specific gravity (USG): means the cat has dilute urine, early in kidney disease this may be the only abnormality found on lab work
• Bacteria in urine: cats with CRD are at a higher risk for urinary tract infections
• Elevated SDMA: a new blood test included in most lab work that can detect chronic kidney disease earlier than we could detect it before
Excessive urination often leads to dehydration; therefore, the most important treatment for kidney failure is fluids. Fluids help maintain hydration and help promote diuresis and dilution of toxins. Intravenous fluids may be administered in the hospital in more serious cases to give the patient an initial “boost” with aggressive therapy. Subcutaneous fluids are administered at home to help maintain kidney function long-term. The amount and frequency of fluids depends on the severity of the kidney disease and the presence of other problems.
Other common treatments for kidney failure include:
• Potassium Supplements: used to increase blood potassium
• Diet change: low protein/low phosphorus diets with other nutrients to help the kidneys
• Antacids: help minimize nausea and gastric ulcers
• Phosphate Binders: used to decrease blood phosphorous levels
• Appetite Stimulants: when appetite is decreasing
• Pet Tinic or other iron and vitamin supplement: provides minerals and vitamins necessary for red blood cell production; helps with anemia
• Amlodipine: to control high blood pressure
• Epogen: human erythropoietin used for severe anemia to stimulate red blood cell production
• Lactulose or Miralax: cats with kidney disease are often prone to constipation and may also require a laxative to keep stools soft
• Antibiotics: when a urinary tract or kidney infections are present
• Azodyl- a probiotic that helps support normal function and health of kidneys
Kidney transplants and hemodialysis are also available for cats but are only appropriate under certain circumstances. Please speak with the doctor if you are interested so we can go over the commitment level needed for successful treatment. These procedures can be done at the University of Pennsylvania School of Veterinary Medicine in Philadelphia.
Staging of CRD
The International Renal Interest Society (IRIS) developed guidelines to stage CRD into four stages depending on the severity of the disease. Stage I is the least severe stage and Stage IV is the most severe stage. We use blood tests (measures creatinine), urine tests (measures protein) and blood pressure measurements to stage your cat’s chronic kidney disease.
IRIS Stage I: Creatinine is less than 1.6 mg/dl
IRIS Stage II: Creatinine is between 1.6-2.8 mg/dl
IRIS Stage III: Creatinine is between 2.9-5 mg/dl
IRIS IV: Creatinine greater than 5 mg/dl
The measurement of blood pressure and urine protein are used to substage the level of kidney disease. The staging helps us to determine the needed treatments and monitoring for your cat’s kidney disease.
Prognosis and Follow Up
Cats with kidney disease need to be monitored by your veterinarian regularly, usually two to six times per year depending on the severity of the disease. Monitoring usually includes:
• Exam: monitor weight, kidney size/shape, body condition, presence of other disease processes that may exacerbate CRD, etc.
• Blood pressure: older cats with CRD are at a higher risk of developing hypertension
• Blood work: used to evaluate the progression of disease, helps us determine which medicines listed above your cat needs
• Urinalysis: evaluates USG, looks for crystals and cells in the urine
• Urine culture: many cats with CRD show no signs of a urinary tract infection, yet their cultures are positive for infections, if left untreated this will exacerbate the kidney disease
• Radiographs: used to look for kidney stones, cancer, etc.
• Ultrasound: used to evaluate the entire urinary tract (kidneys, ureters, bladder), as well as assess the other internal organs for disease processes that may affect your cat’s CRF
Owners should pay attention to appetite, activity level, bowel movement consistency and regularity, hydration status, and weight changes. Bring any concerns to the attention of the doctor as soon as possible. Cats with CRD are susceptible to severe dehydration if they have mild or moderate illness that leads to fluid loses (vomiting, diarrhea) or decreased fluid intake (loss of appetite.) The prognosis for cats with CRD is variable depending on the severity of the disease. While chronic renal failure can be life threatening, many cats that are diagnosed early can live for years with a good quality of life if treated.
How to Give Fluids