Kidney disease in a dog or cat

Despite significant advances in the management of kidney disease in pets, patient mortality remains high. One of the reasons for the high morbidity is the late detection of the disease and consequently the very little space left for effective treatment. This is why early detection of kidney disease is essential and thus allows for effective treatment. Early identification of the disease is all the more important in animal patients as transplantation of the diseased organ is not yet available. 

Kidney damage

The kidneys filter waste products and excess fluid from the bloodstream, which are then excreted from the body in the urine. Quite often, however, they are damaged, for example due to infection, poisonous substances, but also due to ageing.

In cats, for example, kidney failure is one of the most common causes of death. If kidney disease reaches an advanced stage, dangerous amounts of fluid, electrolytes and waste products can accumulate in the body.

Manifestations of the disease

In the early stages of the disease, few symptoms can be observed, and therefore kidney disease may be hidden until significant damage to kidney function occurs.

A good indicator of kidney disease is the concentration of urine, which is either very concentrated or, on the contrary, sparse.

Some of the other most common symptoms of chronic kidney disease include:

• Excessive drinking (polydipsia) and excretion of large volumes of urine (polyuria).
• Increased urine volume in the bladder - can lead to incontinence (leakage of urine), especially at night.
• Vomiting and/or diarrhea.
• Lack of appetite and weight loss.
• Depression in an animal is generally related to increased levels of waste substances in the blood.
• Anemia, which is manifested by pale gums of the animal and general weakness due to low blood cell count.
• General weakness of the animal due to low potassium concentration in the blood.

Diagnosis

New indicators of urinary tract disease, such as the cystatin B test, the SDMA test or the FGF-23 test for cats, are helping to make an early diagnosis.

Cystatin B test - the first veterinary test of its kind to detect kidney damage from urine.

Until now, it has not been possible to detect active or acute kidney injury using a marker of kidney injury. Now, with the Cystatin B Test, a simple urine test, we can detect kidney damage even though clinical signs may not yet be apparent.

Kidney damage is associated with high morbidity and mortality in animal patients. Until recently, however, accurate diagnosis of a patient at the time of kidney damage seemed impossible. In addition to the fact that cats and dogs can exhibit a wide range of manifestations, from few or no clinical signs to those with severe and even complete loss of kidney function, there are many causes of kidney damage. These causes include primary kidney damage or damage secondary to poor blood flow through the kidneys.

We can now achieve better diagnostic and therapeutic outcomes through early detection using the renal biomarker cystatin B in conjunction with active clinical intervention. With mortality rates as high as 60% in some patients, this shift in the investigation of kidney damage may help improve the prognosis of patients.

A recent study by IDEXX showed that 1 in 5 dogs and 1 in 7 cats tested had elevated cystatin B. While this statistic is impressive in itself, even more crucial is the fact that of those patients with elevated cystatin B, 56.4% of the dogs and 35.7% of the cats had other renal functional markers within the reference interval. This suggests the presence of subclinical active kidney damage. In these cases, where renal damage was not yet clinically apparent, any chance of earlier detection of disease and therapeutic intervention would have been missed without cystatin B testing.

The cystatin B test is of significant clinical value in canine and feline patients who may have suffered kidney damage. However, it is also of value in patients who have been previously diagnosed with kidney disease, where it helps to differentiate between stable patients and those with progressive degenerative changes.

SDMA blood test - Innovative biomarker of kidney function

Another option for diagnosing kidney damage is to test the patient's blood serum for SDMA. Symmetrical dimethylarginine (SDMA) is an amino acid that is formed physiologically in the body during the degradation of methylated proteins. Since SDMA is excreted almost exclusively by the kidneys, it is an accurate indicator of kidney function.

SDMA has been shown to be a more reliable indicator of kidney function than creatinine testing, allowing veterinarians to detect acute kidney injury and chronic kidney disease in animals earlier than ever before. The SDMA value increases with as little as 25% loss of kidney function (source: IDEXX). This makes the SDMA test a more accurate indicator for both acute kidney injury and chronic kidney disease. The concentration of SDMA consistently increases in the blood serum of a diseased animal months to years earlier than the serum creatinine concentration. Therefore, simply testing blood creatinine levels cannot identify kidney problems until there is nearly 75% loss of kidney function. In some cases, this may already be too late to determine effective treatment for the animal.

Thanks to the SDMA test, we are able to diagnose twice as many cases of kidney failure in dogs or cats. Data from SDMA testing suggests that the prevalence of kidney disease is twice as high as previously reported.

FGF-23 test for cats

FGF-23 is a renal marker that identifies patient phosphate overload earlier than elevated serum total phosphorus in cats with early-stage chronic kidney disease. Knowing a cat's FGF-23 level provides answers to several questions veterinarians and breeders have: when should a kidney diet be started? Is a lifelong change in the cat's diet necessary? The FGF-23 test provides the breeder with an objective idea of his cat's kidney disease and confirms the decision to pursue a change in the patient's diet that may prolong his life. The FGF-23 test in the early stages of chronic kidney disease in cats also provides tangible evidence to the breeder that the feeding change made is beneficial to their cat.

Regular blood and urine tests

To prevent massive kidney damage, we recommend that every dog or cat has a blood and urine test at least once a year. However, it is still very unlikely that a single biomarker provides all the information needed and each individual marker is more likely to be part of a large puzzle. Serum creatinine, like other biochemical parameters used to date, remains an important indicator of renal function despite diagnostic advances.

X-ray and ultrasound examination of the kidneys

In addition to these examinations, we recommend an X-ray or ultrasound examination of the animal, which examines the size and shape of the dog or cat's kidneys to detect visible structural abnormalities early. Indeed, chronic renal failure often manifests itself by the kidneys being unusually small with an irregular surface.

Ultrasound of the normal kidney

 Ultrasound of the last stage of chronic kidney disease

Warning: This article is for information only and does not replace professional consultation or examination of the animal by a veterinarian. If you have any doubts about the health of your pet, contact your veterinarian immediately. 

17.01.2025