Kidney Disease in Pets: 9 Essential Q&As Debunked by Specialist Vet Dr. Hu Yu-Yen (Part 1)
The kidney is a silent organ. When it
develops disease, symptoms may not necessarily appear, and often there are no obvious
signs. This is why many pet parents only discover that their beloved companions
have chronic kidney disease (CKD) when the illness has already progressed to
later stages.
Even though CKD is very common today, many
pet owners still don’t fully understand it. According to a 2020 survey
conducted by the Taiwan Society of Feline Medicine on 640 cat owners across Taiwan, results showed that 90% of cat
owners were unaware of the symptoms of chronic kidney failure, and nearly 70%
did not know that senior cats over the age of 7 are at high risk for CKD.
In this interview, we focus on the “silent
killer” in dogs and cats — chronic kidney disease — by visiting Dr. Hu Yu-Yen,
Director of the Nephrology Critical Care Department at Chung Hsing Animal
Hospital in Kaohsiung (specializing in kidney research and dialysis treatment
for dogs and cats).
Q1: Most people think
cats are more prone to kidney disease. Among pets visiting for kidney-related
issues today, are there more dogs or cats? Does it relate to breed or age?
In terms of kidney disease, cats are indeed
more common. This is due to multiple factors, including diet, natural habits,
genetic predispositions, and body structure.
- Carnivorous nature: Cats require a
high-protein diet, which places a heavy metabolic load on their kidneys to
process nitrogenous waste and phosphorus. However, cats have fewer
nephrons (the basic functional units of the kidney) compared to humans or
dogs, meaning their kidneys carry a much heavier burden.
- Low water intake: Historically, cats
lived in dry, arid environments (such as deserts). Over time, they evolved
strong kidney function, able to excrete nitrogenous waste with minimal
water. But since they drink less water, combined with fewer nephrons,
their kidneys remain under long-term stress.
- Breed: Overseas studies show that nearly 30%
of Persian-related breeds (such as Persians and Chinchillas) suffer from
polycystic kidney disease. In affected cats, fluid-filled cysts form in
the kidneys, gradually compressing and destroying healthy tissue,
eventually leading to CKD.
- Shorter urinary tracts: Cats’ small body
size means their ureters and urethras are narrower. When dehydration leads
to stone formation, urinary blockages can easily occur, causing post-renal
acute kidney failure.
Although cats dominate CKD cases, many dogs
also develop kidney disease. As pets enter an “aging population,” chronic
diseases emerge more frequently. In dogs, kidney issues often stem from
complications of other illnesses. For example:
- Dogs with periodontal disease may suffer kidney damage due to
bacterial invasion.
- Dogs with arthritis may be prescribed painkillers, which can also
harm the kidneys over time.
Q2: The most common way
to assess kidney health is through Blood Urea Nitrogen (BUN) and Creatinine
(CREA). If these values are normal, does that mean the pet’s kidneys are
healthy?
- BUN is a byproduct of protein metabolism,
used to evaluate the kidneys’ ability to excrete waste.
- Creatinine (CREA) is related to
muscle metabolism — it’s a waste product from creatine breakdown in
muscles, normally excreted by the kidneys.
Together, these are often referred to as uremic
indices.
While BUN and CREA are valuable, kidney
health must be judged with multiple tests. The kidneys are not only responsible
for waste removal but also regulate electrolytes, acid-base balance, hormones,
red blood cell production, and blood pressure. Thus, imbalances in electrolytes
or anemia may also indicate kidney dysfunction.
Limitations:
- BUN can be influenced by many factors. For
example, gastrointestinal inflammation or bleeding can increase BUN, while
poor liver function may decrease it.
- CREA is not ideal for early detection. Since older pets have less muscle mass, creatinine levels may appear “normal” even if kidney function is already impaired — leading to falsely low readings.
A newer marker, SDMA (Symmetric
Dimethylarginine), rises rapidly when kidney function begins to decline,
allowing much earlier detection of kidney disease. Currently, SDMA is
considered the most reliable indicator.
Additionally, urinalysis (checking for
protein, crystals, or stones) and imaging (X-rays, ultrasounds for
kidney shrinkage, cysts, or tumors) are also used.
In conclusion: these three indices (BUN, CREA, SDMA) are not absolute, but together they provide important guidance for diagnosing kidney problems in dogs and cats.
Q3: Why do pets with CKD
often have fluctuating appetites? Should we let them eat as much as they want
when they do have an appetite? Is it safe to use appetite stimulants long-term?
CKD in dogs and cats is divided into four
stages. From mid-stage 2 to stage 3, pets often begin to show anorexia,
with inconsistent appetite.
As kidney function declines, uremic toxins
accumulate in the body. The first system affected is the gastrointestinal
tract. This leads to symptoms such as:
- Uremic odor in the mouth
- Oral ulcers
- Nausea and discomfort — all reducing the desire to eat
As long as obesity isn’t an issue, we
encourage CKD pets to eat as much as possible. Eating gives them the strength
to survive. Appetite stimulants are often prescribed to help them eat, drink,
and move more, which supports waste excretion and reduces kidney strain.
While medications are useful, some also rely
on the kidneys for metabolism. Supplements can provide a gentler alternative.
For instance, Hi-Q Pets’ “RenoShield” contains the unique compound Fucobalan®
(a blend of oligo fucoidan and Laminaria Japonica Extract), a natural nutrient
extracted from clean water brown seaweed, which may boost appetite without
burdening the kidneys.
For overweight CKD pets, muscle condition is
also important. If muscle loss is diagnosed, high-quality protein must still be
included in the diet to maintain muscle mass.
Q4: Veterinarians usually
recommend prescription diets for CKD pets. Is feeding prescription food enough
to solve the problem? What if they refuse to eat it?
Prescription diets are designed through
extensive research to meet the nutritional needs of CKD pets. Key features
include:
- Low but high-quality protein, reducing nitrogenous waste buildup
- Reduced phosphorus and sodium, helping to control blood pressure
Studies show CKD pets on prescription diets live twice as long as those not fed these diets. Therefore, we recommend starting prescription diets as early as stage 1.
However, prescription diets may not taste
appealing. For pets with poor appetite, refusal is common. Yet eating is
critical. Lack of muscle mass accelerates CKD progression and weakens the
pet’s ability to survive.
Alternatives include:
- Prescription wet food or canned food
- Boiled lean meats or senior pet food
- Using phosphate binders to reduce phosphorus levels in
non-prescription food
If possible, minimizing drug use is best.
Supplements that improve appetite can also support better food intake.
Q5: For pets already
diagnosed with CKD, can supplements be used together with medications?
By stage 3 CKD, veterinarians usually
prescribe multiple medications: appetite stimulants, phosphate binders,
gastrointestinal drugs, and pain relievers.
From my clinical experience, the best
approach is to give them at different times, especially phosphate
binders. Since phosphate binders are mixed with food to bind certain nutrients,
they may reduce the effectiveness of other medications or supplements.
Recommended schedule:
- Before meals (empty stomach):
appetite-boosting supplements
- With meals: phosphate binders
- 30–60 minutes after meals:
gastrointestinal and pain-relief medications
If pet parents cannot manage three separate dosing times, giving supplements together with food and medications is still acceptable.
Reference: https://www.hiq-pets.com/article/87
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