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Kidney disease in cats is one of the most common diseases that affect cats. The kidneys are part of the urinary tract. The cat’s urinary tract is a system made up of the kidneys, ureters, urinary bladder and urethra. These organs work together to produce, transport, store, and excrete urine. The main job of the urinary tract is to rid the cat’s body of waste materials and to control the volume and composition of the body fluids products. The term “renal” is another word for “kidney”.
A disease can strike any part of the urinary tract. For example, cancer can develop in the kidney, ureter, bladder or urethra. Some people mistake diseases of other parts of the urinary tract for kidney disease and vise versa. The symptoms of diseases of the kidney can be similar to other parts of the urinary tract. It is also possible to have more than one problem in the urinary tract such as an infection in both the bladder and kidneys. Below we will specifically focus on symptoms of kidney disease.
Signs of Kidney Disease in Cats
The signs of kidney disease in cats can vary depending on the type of disease affecting the kidney. Signs may include:
- Abdominal distension
- Abdominal pain
- Back pain
- Blood in the urine
- Decreased urine production
- Excessive drinking
- Excessive urination
- Frequent urination
- Loss of appetite
- Malodorous urinations
- Oral ulcerations
- Painful urination
- Recurrent urinary tract infections
- Straining to urinate
- Weight loss
Different Types of Kidney Disease in Cats
The kidneys can develop several different problems that include:
- Kidney Cancer – Renal neoplasia is a relatively uncommon cancer located in the kidney. Renal neoplasia can originate in the kidney (primary) or spread to the kidney from another site (secondary). Most renal tumors are seen in middle-aged to older cats. Renal lymphoma is a type of cancer more common in cats that are feline leukemia virus positive. Generally, there are no specific causes for kidney cancer.
- Kidney Stones – One function of the urinary system is the removal of body wastes in liquid form. Some mineral wastes are only slightly soluble and may form crystals. If the transit time of crystal movement through the urinary system is prolonged, crystals may interact and grow into stones. Several types of stones can affect cats. Each type of stone is often associated with its own specific cause. Nephrolithiasis, also known as renal calculi or kidney stones, can develop in cats.
- Pyelonephritis – Pyelonephritis is an inflammation of the kidney. We generally refer to pyelonephritis as a bacterial infection of the upper urinary tract including any part of the kidney.
- Polycystic Kidney Diseases – This disease is caused by abnormal cyst formation in young cats. It is a slowly progressive, irreversible, inherited kidney disease. It is characterized by development of cysts in the kidney and sometimes also the pancreas, liver and/or uterus. Ultimately, PKD can result in renal failure, with clinical signs similar to those of cats with naturally occurring kidney failure.
- Chronic Kidney Disease in Cats – Chronic renal failure, commonly referred to also as chronic kidney failure and abbreviated as CRF, is a common problem in cats. The digestion of food produces waste products, which are carried by blood to the kidneys to be filtered and excreted in the form of urine. When the kidneys fail, they are no longer able to remove these waste products, and toxins build up in the blood producing clinical signs of kidney disease. All breeds of any age can be affected. However, older cats are commonly affected as the prevalence increases with age.
- Acute Kidney Failure in Cats – Acute kidney failure (acute renal failure or ARF) is characterized by an abrupt decline in kidney function that leads to changes in the chemistry of the body including alterations in fluid and mineral balance. The changes that arise as a result of ARF affect almost every body system. It can be caused by a urinary obstruction and various toxins including antifreeze.
- Kidney Parasites– Renal parasites are worms that invade the urinary tract and cause disease. Some affected cats have no clinical signs, especially with Capillaria species. Some cats may be extremely ill if they have associated kidney failure or severe infection.
- Renal (Kidney) Amyloidosis – This is a disease that results from the abnormal deposition of amyloid protein throughout the body. Amyloid results from the body’s inability to break down certain proteins in the body. This results in accumulation of amyloid outside body cells which builds up and injures normal cells.
- Glomerulonephritis – This is a kidney disorder caused by inflammation of glomerulus which is the microscopic part of the kidney that filters the blood. It is usually caused by immune complexes (clusters of antibodies and antigens) that get deposited onto the glomeruli, causing them to malfunction. The immune complexes develop secondary to some other disease process that is going on in the cat’s body.
- Untreated, glomerulonephritis can lead to chronic kidney failure.
- Chronic obstructive uropathy (hydronephrosis) – This is a disease caused by obstruction (blockage) of the ureter (the tiny tubular structure that allows the passage of urine from the kidney to the urinary bladder) that results in distension (enlargement) of the pelvis (inside) of the kidney with urine. This can lead to renal failure.
Diagnosis of Kidney Disease in Cats
Diagnostic tests may be recommended on a case-by-case basis. Diagnosis of kidney disease in cats is often made by the following diagnostic tests:
- Complete medical history
- Complete physical examination
- A biochemistry analysis (biochemical profile tests), such as serum creatinine and BUN concentrations are typically elevated with CRF.
- Serum phosphorus and potassium concentrations may also be increased.
- Complete blood count (Hemogram; CBC) may be performed to evaluate for signs of infection, inflammation, anemia or platelet abnormalities.
- Urinalysis tests may show a low specific gravity, which is common with CRF, signs of infection, abnormal urine protein or sediment may indicate infection or glomerular disease or parasites.
- Urine culture should be performed to evaluate for the presence of upper or lower urinary tract infection.
- Abdominal radiographs (X-rays) may show small kidney size, which is common with CRF, but normal renal size does not rule out CRF.
- Some chronic kidney diseases in cats can be associated with enlarged kidneys (e.g. polycystic renal disease, renal lymphoma).
- Renal ultrasonography – can provide additional information about the kidneys. Kidneys with chronic disease are typically small and sometimes irregularly shaped. Large kidneys may indicate polycystic renal disease, cancer or an acute kidney disease. Some cats can have a normal ultrasound with CRF.
- Urine protein/creatinine ratio – this is useful to evaluate urinary protein loss in cats suspected to have glomerular disease.
- Arterial blood pressure may be needed to determine the presence of complicating hypertension (high blood pressure).
- Excretory urography may be useful in the evaluation of abnormalities in renal size, shape or location. It may also be valuable in the detection of obstruction, cancer or stones.
- Blood gas analysis will allow evaluation of acid-base levels.
- Leptospira antibody serologic tests may be needed to diagnose this infection.
- A fine needle aspiration (biopsy) of the kidney may be useful in some cats with renal diseases (e.g. kidney lymphoma, granulomatous interstitial nephritis due to FIP).
- Endogenous or exogenous creatinine clearance can be used to measure glomerular filtration rate in CATS with normal blood work who are suspected to have renal disease.
- Fractional excretion of electrolytes (sodium, potassium, chloride, and phosphorus) may be useful in evaluation of animals with suspected renal tubular disorders.
- Radioisotope clearances may be used to determine kidney filtration and blood flow.
- Symmetric Dimethylarginine (SMDA) Blood Testing – SMDA is a test to look for a blood protein that is known to increase as kidney function declines. It will start to increase before the blood creatinine.
Reference Articles about Kidney Disease in Cats:
- Polycystic Kidney Disease in Cats
- Kidney Disease in Cats: Everything Cat Owners Need to Know
- Chronic Kidney Disease in Cats
- Acute Kidney Failure in Cats
- What Cat Owners Need to Know About a Kidney Infection in Cats
- Painful Bladder Syndrome in Cats
- Feline Interstitial Cystitis
- Feline Urinary Obstruction
- The Fine Art of Litter Box Care
- 8 Common Reasons Cats Won’t Use the Litter Box
- Structure and Function of the Urinary Tract in Cats
- What’s the Latest on Feline Urinary Problems?
- Trouble Urinating in Cats (Dysuria)