Article published 2019 – updated 2026
The relationship between microbiota and kidney disease is one of the most interesting topics in recent years, the microbiota interferes with kidney function through its own metabolites, such as trimethylamine (TMA) and short chain fatty acids (SCFAs).
In 2019 I wrote:
“In a few years, we will no longer talk about uremia, but about indole sulfate and p-cresol.”
2026: today everyone, including veterinarians, is finally starting to talk about it.
Uremic toxin: indole sulfate and the microbiota
Indole sulfate, is a metabolite of dietary tryptophan that acts as a cardiotoxin and uremic toxin.
In humans, high concentrations of this metabolite in the blood are associated with the development and progression of chronic kidney disease, being a uremic toxim, it stimulates glomerular sclerosis and renal interstitial fibrosis.
Studies suggest that:
Patients with CKD develop higher plasma TMAO levels and a different composition of the gut microbiota than healthy subjects.
The increase in TMAO levels in patients with CKD is directly caused by microbiota dysbiosis.
- TMAO (trimelitalamine-N-oxide) → cardiovascular risk and thrombosis
- Indoxyl sulfate → progression renal disease thrombosis, cardiovascular disease, anemia
- p-cresyl-phosphate → progression of renal and vascular disease, pro-inflammatory effects
The microbiota produces some of the most important uremic toxins
In chronic renal failure, the intestinal microbiota is directly involved in the increase in these uremic toxins, because it is the dysbiosis induced by uremia itself that increases the concentrations of toxins in the circulation with a consequent reduction in renal excretion and worsening of the disease.
Fecal microbiome and serum indole sulfate concentrations are higher in cats with chronic kidney disease
While gut dysbiosis has been documented in humans with chronic kidney disease (CKD), it is thought to contribute to the production of uremic toxins such as indole sulfate and p-cresol sulfate, including in cats and dogs with chronic renal failure.
In one study, fecal samples from 30 client-owned cats in stage 2 and stage 4 renal disease were analyzed to measure serum concentrations of indole sulfate and p-cresol sulfate.
FIND OUT HOW I TREAT AND HOW YOU SHOULD TREAT THE INTESTINE IN THE COURSE OF CHRONIC KIDNEY FAILURE!
Results:
Cats with CKD had reduced diversity and richness in fecal bacteria. The concentration of indole sulfate was significantly increased in cats with CKD, and cats with stage 2 CKD had a burden of uremic toxins very similar to that of cats with advanced disease.
Modulate the microbiota of dogs and cats to cause them to produce fewer uremic toxins
with the administration of
- ⦁ Inulin
- ⦁ Synbiotics and Probiotics: with at least 9 strains including streptococcus, bifidobacteria and lactobacilli
- YAKULT
When we talk about Chronic Kidney Failure (CKD) in cats and dogs, we almost always focus on creatinine, urea, and phosphorus. However, the most recent scientific research has revealed a “hidden enemy” that plays a crucial role in the progression of the disease: the alteration of the Gut Microbiota.
In this article, we delve into the Gut-Kidney Axis, understanding why treating the gut is crucial to protect the kidneys.
The Intestine-Kidney Axis: A Dangerous Connection
The kidneys and intestines are constantly communicating. In a healthy animal, this communication is balanced. In a nephropathic animal, a destructive vicious circle is triggered:
- Uremia alters the intestine: The accumulation of urea in the blood (typical of kidney failure) changes the intestinal environment.
- Dysbiosis: “Good” bacteria (such as Lactobacilli) die, while proteolytic (protein-eating) “bad” bacteria proliferate.
- Poison Production: These nasty bacteria produce potent uremic toxins.
- Kidney damage: These toxins are absorbed, enter the blood and affect the kidneys again, accelerating sclerosis and renal fibrosis.
What is Dysbiosis in CKD?
Intestinal dysbiosis is a qualitative and quantitative imbalance of the bacterial flora. In cats and dogs with kidney failure, dysbiosis is not only a consequence, but an aggravating factor.
The uremic environment selects bacteria capable of degrading proteins and amino acids, transforming them into toxic substances rather than nutrients.
Uremic Toxins: Wear Sulfate and P-Cresol
The two most dangerous substances produced by intestinal dysbiosis in renal patients are:
- Wear Sulfate: It comes from the fermentation of Tryptophan. It is directly toxic to the tubular cells of the kidney and stimulates fibrosis (scarring of the kidney).
- P-Cresyl Sulfate (P-Cresol): It derives from the fermentation of Tyrosine and Phenylalanine. It is associated with systemic inflammation and oxidative stress.
These toxins don’t just damage the kidneys: they’re also responsible for anemia (reducing erythropoietin), cardiovascular damage, and bone disease associated with CKD.
Leaky Gut: When the intestine becomes a sieve
In addition to producing toxins, dysbiosis and inflammation damage the intestinal barrier. The so-called “Leaky Gut Syndrome” occurs.
The junctions between the intestinal cells loosen, allowing the passage into the blood not only of uremic toxins, but also of live bacteria (bacterial translocation) and endotoxins. This causes chronic systemic inflammation that drastically worsens the prognosis of the cat or dog.
Treatment Strategies: How to Break the Vicious Cycle
To manage the gut-kidney axis, the classic renal diet is not enough. An integrated approach is needed:
- Protein reduction (but high quality): The less protein that reaches the colon undigested, the less “food” the bad bacteria will have to produce toxins.
- Prebiotics and Fibers: The use of fermentable fibers changes the intestinal pH and feeds the good bacteria.
- Specific probiotics: The integration of selected strains (as in Enteric Dialysis) helps to restore eubiosis and consume nitrogenous waste before it is absorbed.
Frequently Asked Questions (FAQs)
How do I know if my cat has dysbiosis? If your cat suffers from chronic kidney failure, it is almost certain that they also suffer from dysbiosis. Common symptoms may include nausea, vomiting, malformed stools or constipation, and uremic breath (ammonia smell).
Are probiotics only for diarrhea? No. In the case of kidney failure, probiotics are not only used to regulate the stool, but to reduce the production of toxins (such as indoxyl sulfate) that destroy the kidney.
Does nutrition affect the microbiota? Absolutely. A properly formulated kidney diet reduces the protein substrate that bad bacteria use to create toxins. It is the first fundamental step of therapy.
Probiotics for Chronic Kidney Failure in Cats: 2026 Scientific Comparison of Vivomixx, Probinul 5, Visbiome, Azodyl and Nephrodyl
Disclaimer: The Contents Are For Informational Purposes Only And Under No Circumstances Can They Constitute A Prescription Of A Treatment Or Substitute For A Specialist Visit Or Direct Relationship With Your Veterinarian/Doctor. All information reported here is derived from bibliographic sources, personal experiences and clinical studies in the public domain. The information disseminated on the site is published after careful verification of the sources, carefully chosen and as far as possible updated and official. All Information On Special Diets And Food Supplements For Pets Is For Informational Purposes. This information serves as a general guideline, it cannot be applied to all pets or considered as alternatives to professional advice. In these pages are inserted and presented alternative therapy and homeopathic remedies of unscientifically validated efficacy and without approved therapeutic indications. The products are not intended as a substitute for a varied and balanced diet and must be used as part of a healthy lifestyle. Disclaimer and Terms
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