What are the symptoms of kidney disease in cats? A veterinarian explains the symptoms and treatments in detail.

Several years ago, a substance related to kidney disease in cats was identified and gained media attention.

It has become widely known not only among cat owners but also among those who do not own cats that they are prone to kidney disease. Chronic kidney disease is common in elderly cats; 30–40% of cats over 7 years old and 80% of cats over 15 years old suffer from it, making kidney disease the number one cause of death in cats.

In this article, we will explain kidney disease in cats.

What is kidney disease in cats?

There are two types of kidney disease in cats: acute kidney disease (acute renal failure) and chronic kidney disease (chronic renal failure).

Acute kidney disease

Acute kidney disease is a condition where blood does not circulate through the kidneys due to hemorrhage or a drop in blood pressure, preventing the excretion of bodily waste products in urine. The primary causes include reduced blood flow to the kidneys due to hemorrhage or surgery. It can also be caused by toxins, drugs, or poisonous plants that affect the kidneys. Representative examples include poisoning from ethylene glycol, which was found in older types of antifreeze, or arsenic in rat poison.

Chronic kidney disease

Chronic kidney disease occurs when the kidneys are damaged for several months or longer. Chronic renal failure does not heal even with treatment and continues to progress gradually, eventually leading to end-stage renal failure or uremia.

As a test for kidney function, blood urea nitrogen (BUN) and creatinine are evaluated via blood tests, but these indicators only show abnormal values once approximately 75% of kidney function has been lost. Recently, an evaluation index for kidney function called SDMA has also emerged. Because SDMA shows abnormalities when about 40% of kidney function is lost, it is gaining attention as an index that allows for earlier diagnosis of kidney disease.

Chronic kidney disease is common in senior cats over 7 years old and is the number one cause of death. Furthermore, it is believed that kidney function begins to decline gradually from around 5 years of age. While the main cause remained unclear for many years, it has recently been revealed that a substance called "AIM" is related to kidney aging and that AIM does not function in cats. There is high expectation that AIM could potentially become a therapeutic agent for kidney disease in cats.

Abyssinians and Persians have a genetic predisposition to kidney disease. In addition, a condition called polycystic kidney disease is common in breeds such as Persians and Exotic Shorthairs, leading to a higher tendency to develop chronic kidney disease. Furthermore, long-term urinary stones or bladder stones can also lead to chronic kidney disease.

What symptoms occur when a cat has kidney problems?

We will explain the symptoms of acute and chronic kidney disease respectively.

Symptoms of acute kidney disease

Acute kidney disease causes sudden lethargy, loss of appetite, vomiting, and diarrhea. Additionally, the amount of urine produced may decrease or stop altogether. Hypothermia is also a common occurrence.

Symptoms of chronic kidney disease

Chronic kidney disease has four stages, with symptoms varying by stage.

Early stage (Stage I)

There are no symptoms in the early stage. This is a period where no abnormalities are found in blood or urine tests.

Middle stage (Stage II)

Mild loss of appetite, weight loss, increased thirst, and increased urination begin to occur. In urine tests, urine specific gravity (urine concentration) begins to drop, resulting in diluted urine.

In blood tests, creatinine and urea nitrogen levels range from normal to slightly elevated.

Late stage (Stage III)

Upon entering the late stage, blood urea nitrogen and creatinine levels rise. Because kidney function is significantly reduced, the urine becomes dilute.

Appetite decreases, and weight loss occurs. Vomiting also begins. Anemia occurs because the erythropoietin (a hematopoietic hormone) produced by the kidneys decreases. Even if the cat drinks water, it is not absorbed by the body but is excreted as urine, leading to dehydration. If you pinch the skin on the back and it is slow to return to its original position, this is a sign of dehydration.

Elderly cats examined at veterinary clinics are frequently diagnosed with Stage II or III chronic kidney disease.

End stage (Stage IV)

The end stage is also called the uremic phase, where symptoms of uremia manifest. Appetite is completely lost, and the cat vomits frequently. The cat becomes very emaciated, and severe dehydration occurs. It is also common for the body to emit a smell of urine. Convulsions can also occur due to uremia. Anemia progresses, causing the inside of the mouth to look pale. Stomatitis also becomes more likely.

Once the end stage is reached, significant life extension is not expected even with treatment.

Is feline kidney disease curable? What are the treatments?

Since treatments differ for acute and chronic kidney disease, we will explain each.

Treatment for acute kidney disease

Acute kidney disease is a condition with a very high chance of improvement if the underlying cause is resolved. Therefore, the first step is to perform thorough testing to identify the cause.

In cases of acute kidney disease, severe dehydration may be present. IV fluids are administered rapidly to correct the dehydration. Since electrolyte imbalances often occur, these are also corrected. Anti-nausea medication is used to manage the vomiting associated with acute kidney disease.

In facilities capable of performing dialysis (peritoneal dialysis), dialysis therapy may also be conducted.

Treatment for chronic kidney disease

For chronic kidney disease, unfortunately, there is no definitive cure at this stage. All treatments are aimed at slowing the progression of the disease or managing the symptoms.

Treatment for chronic kidney disease varies by stage.

In the early stages, dietary therapy is implemented to support the kidneys.

In the middle stage, dietary therapy remains the mainstay, similar to the early stage. Additionally, antihypertensive drugs may be used to suppress the progression of kidney disease. Supplements with antioxidant properties are also considered effective.

Upon entering the late stage, appetite decreases due to nausea and other factors. While dietary therapy is the foundation, fluid therapy becomes necessary. Fluid therapy is generally administered daily. IV fluids are used to improve dehydration, and anti-nausea medication is also utilized. In cases of severe anemia, hematopoietics may be used.

In the end stage, fluid therapy is the primary treatment. If the facility can perform dialysis, it is conducted. Because the cat will stop eating, nutritional support via a catheter also becomes necessary. Since anemia becomes quite advanced, blood transfusions are sometimes performed.

Summary

Kidney disease can be fatal for cats. Especially in the case of chronic kidney disease, no curative treatment has been established, and the main goal is to slow down the progression as much as possible.

Chronic kidney disease has almost no symptoms in the early stages and is usually discovered accidentally through health checkups. By the time symptoms appear and the cat is taken to the clinic, the disease has usually reached an advanced stage.

To detect kidney disease at an early stage, health checkups one to two times a year and the daily observational skills of the owner are crucial.