Mary Allen
In old age, cats suffer more often than average from chronic kidney failure (CRF), also known as chronic kidney disease (CKD). This is a long-term loss of function in the kidneys’ ability to concentrate. The disease progresses and the damage is irreparable so that the cat only shows symptoms such as vomiting, fatigue, or life-threatening electrolyte imbalances after a certain degree of kidney damage.
Function and Structure of the Kidneys
The kidneys serve the cat as the central organ for the water and electrolyte balance as well as for the excretion of toxic metabolic products by excreting urine. They are shaped like a bean and are located on the roof of the abdominal cavity in cats. In contrast to dogs, they are about the same in cats.
The organs with a strong blood supply are made up of a superficial kidney capsule, a kidney cortex, and a kidney medulla. Within these structures, there are numerous functional units (nephrons), which consist of the renal corpuscles (glomerular) of the renal cortex and the renal tubules (tubules) of the renal medulla. Finally, in the lower part of the kidneys, there is the renal pelvis, which collects the urine produced and directs it into the ureter towards the urinary bladder.
How Does Renal Insufficiency Develop in Cats?
Various diseases and stimuli can damage the cat’s kidneys to such an extent that acute (sudden) or more often chronic (long-term) kidney failure occurs:
- Hereditary and acquired kidney diseases: genetic cysts, tumors of the kidneys or surrounding organs (e.g. adrenal glands), autoimmune diseases, kidney stones, circulatory disorders (ischemia)
- Infectious causes (e.g. feline infectious peritonitis FIP)
- Toxic substances (e.g. plants, medicines, pesticides, heavy metals)
- A unilateral feed with too high a proportion of phosphorus
Symptoms: How is Kidney Failure in Cats Recognized?
Older cats seem to be particularly affected by kidney disease. However, this is due to the kidneys being quite capable of compensating. If the kidneys are damaged, they work without restrictions up to a certain degree of damage to the functional units (around 75%). However, if this threshold is exceeded and too many nephrons break, the cat usually shows a clinic for the first time at an advanced age. The following symptoms are often observed:
- Weak general well-being: tiredness, reluctance to move, loss of appetite, and weight loss
- The cat’s dull coat makes it look less well-groomed
- Increased urination and dehydration
- Fluctuations in the electrolyte balance (e.g. increased potassium concentration in the blood): cardiac arrhythmias
- Water retention (edema)
- High blood pressure and resulting cat blindness
- The decreasing excretion of toxic metabolic products such as ammonia can lead to signs of poisoning such as vomiting, diarrhea, and bad breath
- Cats can die as a result of kidney failure
What Diagnostic Options are There?
It is known that cats are particularly likely to develop kidney disease. It is therefore particularly important to consult a veterinarian at an early stage if you experience the symptoms described above.
Information about the first appearance of the clinical signs as well as the vaccination status or possible ingestion of toxic substances is extremely helpful so that the latter can better classify the course of the disease.
If the cat shows a severely weakened general condition or already acute life-threatening signs such as cardiac arrhythmias during the visit to the vet, immediate intervention by the vet is necessary. In this case, the electrolyte fluctuations and the fluid deficit are balanced out with infusions.
This is followed by a special examination of the kidneys, which begins with palpation of the kidneys in the upper abdomen. The veterinarian can already determine sensitivity to pain and abnormal structural changes in the kidneys, such as differences in size or formation.
The latter can then be viewed more precisely using imaging measures (e.g. X-ray or ultrasound). In contrast to structural changes, kidney function can only be determined using special blood and urine tests, the results of which can classify the disease as acute or chronic kidney failure. These include in particular the following parameters:
- in the blood: substances requiring urine (e.g. creatinine, urea, SDMA), electrolytes (e.g. potassium), acidosis of the blood
- In the urine: the specific gravity (a measure of the kidneys’ ability to concentrate), protein content
How Can Kidney Failure in Cats be Treated?
The therapy of renal insufficiency is divided into a kidney diet and supportive measures:
Kidney diet
The quality of life of cats with kidney disease can be greatly improved by a balanced diet that is gentle on the kidneys. The aim of these diets is to lower toxic metabolic products in the body and to compensate for electrolyte and vitamin deficiencies through the following composition:
- Low in phosphorus and, if necessary, additional administration of phosphate binders
- Rich in easily digestible proteins
- High in carbohydrates
- low salt content (against high blood pressure)
- Addition of vitamins (e.g. D, B) and high-quality fatty acids (e.g. omega-3 fatty acids)
Important: The blood of the sick cat should always be checked by a veterinarian on a regular basis. As long as the blood values do not improve, the kidney diet should not be discontinued. Cat treats should also be avoided, as they often contain high levels of phosphorus and low-quality proteins.
Supportive measures
Concomitant symptoms can be alleviated with supportive therapy:
- Vomiting: stomach protection tablets
- Infections: possibly antibiotics or antivirals
- Pain: pain medication
What is the Prognosis?
Once the kidneys are damaged, they cannot recover from the damage. Nevertheless, an early diagnosis and a kidney diet can in some cases greatly reduce the consequences of kidney failure and improve the cat’s lifespan and quality of life.
How Can Kidney Failure in Cats be Prevented?
Although the causes of kidney failure are diverse, a healthy diet can prevent the disease from occurring. Ordinary commercially available cat foods are often high in phosphorus and low-quality proteins, which can overwhelm the kidneys.