Chronic Kidney Disease & the Gut Microbiome

Chronic Kidney Disease & the Gut Microbiome

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The kidneys play a vital role in maintaining the overall health of animals and people. They regulate hydration and act as a filter to aid in the removal of waste from the bloodstream. In this context waste refers to the breakdown of substances such as food, old cells, and medication. This waste is filtered through the kidneys and excreted via the urine. The kidneys also aid in the regulation of blood pressure, production of red blood cells, calcium homeostasis, and many other crucial functions.

Chronic Kidney Disease:

In general practice, we are often presented with animals that have developed chronic kidney disease (CKD). CKD means a diagnosis that has been present for months to years. Animals with underlying CKD can display a variety of clinical symptoms which may include; increased thirst (polydipsia), increased urination (polyuria), decreased appetite, weight loss, vomiting, or general weakness. When an animal is diagnosed with kidney disease, they are staged according to the IRIS (International Renal Interest Society) guidelines. The stages range from 1 to 4 with 1 being early disease and 4 being late-stage disease. Depending on the stage of kidney disease as well as the animal’s species, the appropriate therapy is aimed at maintaining and supporting the remaining kidney function. This is often achieved through prescribing a renal diet which is designed to have low levels of highly digestible protein. Renal diets also treat underlying hypertension and proteinuria. Proteinuria is when excess protein is lost via the kidneys due to declining function. Another important factor in treating kidney disease is maintaining hydration and reducing the accumulation of waste in the bloodstream.

So how does CKD affect the gut microbiome?

When kidney function is impaired, the kidneys can no longer filter out waste normally. Failure to eliminate excess waste results in an accumulation of waste in the bloodstream which is known as uremia. When this buildup of waste circulates in the bloodstream it can cause an imbalance of bacteria in the gut microbiome resulting in an increased production of toxins by the gut [1]. This disruption of the gastrointestinal flora, also known as dysbiosis, can cause an increase in permeability of the intestinal lining, promote inflammation, and negatively affect the overall immune system [2]. Increased permeability of the intestinal lining allows further translocation of these toxins into circulation which can enhance the progression of kidney disease.

How Can Probiotics Help?

There is growing research on potential therapies designed to support a healthy gut microbiome to slow the progression of CKD in patients. A study performed on dogs examined the effects of probiotics on the Glomerular filtration rate (GFR) in patients with CKD. GFR is a measurement of how well the kidneys are functioning. This study had two groups of dogs in various stages of kidney disease. Both groups received a renal diet, but only one of the groups was administered a probiotic. Additional conditions related to CKD, such as hypertension, were treated accordingly. At the end of the two-month study, the data concluded that the group of dogs that received the probiotic had a higher (improved) GFR at the end of the study, whereas the control group had a significantly lower GFR [3]. A similar study examined the effects of the probiotic Bifidobacterium animalis, when administered to rats with CKD. It determined that this supplementation lowered circulating toxin levels and slowed the progression of kidney disease [4]. In conclusion, studies show there is value in considering the role of the gastrointestinal tract when treating CKD patients. Incorporating probiotic therapeutics to support a healthy microbiome can help slow the progression of chronic kidney disease.