A dog with diarrhea and kidney disease may be experiencing gastrointestinal effects of advanced kidney dysfunction, but the two symptoms do not always have the same cause.
Kidney disease can contribute to diarrhea when waste products accumulate in the bloodstream and affect other organs, particularly in more advanced stages. However, diarrhea is also extremely common with primary digestive problems such as dietary indiscretion, infections, parasites, inflammation, and food intolerance.
The combination deserves closer attention when diarrhea occurs in a dog already diagnosed with kidney disease. Diarrhea can cause substantial fluid and electrolyte losses, which may be particularly problematic for a dog whose kidneys are already impaired.
A veterinarian may need to determine whether the kidney disease is worsening, whether dehydration is developing, or whether a separate gastrointestinal illness is responsible.
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Dog Diarrhea and Kidney Disease: Why It Happens
Diarrhea can occur in a dog with kidney disease because reduced kidney function can allow waste products to accumulate in the bloodstream, which may cause nausea and gastrointestinal irritation.
Dogs with more advanced kidney disease may also experience changes in appetite, vomiting, dehydration, and diarrhea.
Medications, dietary changes, dehydration, or another gastrointestinal illness can also cause diarrhea in a dog that happens to have kidney disease. This distinction is important because diarrhea can cause additional fluid and electrolyte losses, potentially placing further stress on already impaired kidney function.
Dog Diarrhea and Kidney Disease: Common Causes
Advanced Kidney Disease and Uremia
As kidney function becomes severely impaired, waste products that would normally be eliminated in urine can accumulate in the bloodstream. This is particularly associated with advanced kidney disease and uremia.
Dogs in advanced stages may develop gastrointestinal signs including vomiting, poor appetite, dehydration, weight loss, and diarrhea.
If a dog with established kidney disease suddenly develops diarrhea together with worsening appetite, vomiting, weakness, or dehydration, the veterinarian may need to reassess the severity of the kidney disease and its complications.
Related: Dog With Congestive Heart Failure and Kidney Disease
Dehydration From Kidney Disease
Dogs with chronic kidney disease may lose some of their ability to concentrate urine and can therefore urinate more and drink more water. In advanced disease, maintaining adequate hydration can become increasingly difficult.
Diarrhea adds another source of fluid loss. A dog with kidney disease may consequently become dehydrated more easily when diarrhea is persistent or severe.
Dehydration can also complicate the interpretation and management of kidney function, making veterinary assessment important when fluid losses are significant.
Related: Dog shaking panting and kidney disease (What it means)
A Separate Gastrointestinal Infection
A dog with kidney disease can still develop gastroenteritis caused by infection. Bacterial, viral, or other gastrointestinal infections can cause diarrhea, sometimes accompanied by vomiting, poor appetite, fever, or lethargy.
In this situation, the diarrhea may have little to do with the underlying kidney disease.
The veterinarian may consider recent exposure to other dogs, changes in environment, boarding, diet, and other risk factors when determining the cause.
Gastrointestinal Parasites
Intestinal parasites can cause diarrhea in dogs. Depending on the parasite and severity of infection, affected dogs may also develop weight loss, poor growth, anemia, or blood in the stool.
A dog with kidney disease can become infected with intestinal parasites just like any other dog.
Fecal testing may therefore be appropriate when diarrhea persists, or the history suggests parasitic disease.
Dietary Indiscretion or Food Intolerance
Eating unfamiliar, rich, spoiled, or inappropriate food can cause acute diarrhea. Food intolerance and other diet-related digestive problems can also produce recurring gastrointestinal signs.
These problems can occur independently of kidney disease.
For a dog with kidney disease, however, dietary changes should be discussed with the veterinarian because nutritional management may already be an important part of kidney care.
Chronic Gastrointestinal Disease
Long-lasting or recurrent diarrhea can result from chronic enteropathies, including inflammatory intestinal disease and other disorders affecting digestion or absorption.
Chronic enteropathies are generally characterized by gastrointestinal signs lasting at least several weeks and may include diarrhea, vomiting, appetite changes, and weight loss.
If diarrhea continues despite appropriate management of kidney disease, a separate gastrointestinal disorder may need to be investigated.
Medication-Related Diarrhea
Some medications can cause gastrointestinal upset, including diarrhea, in some dogs. This can be particularly relevant when a dog with kidney disease has recently started a new medication or had its treatment changed.
Medication effects should be considered alongside the timing of the diarrhea rather than assuming that worsening kidney disease is responsible.
Do not stop or alter prescribed medication without discussing it with the veterinarian.
Acute Hemorrhagic Diarrhea Syndrome
Sudden, severe bloody diarrhea can occur with acute hemorrhagic diarrhea syndrome, a condition characterized by acute onset of hemorrhagic diarrhea and often vomiting. Significant fluid loss can occur rapidly.
This is not simply a typical manifestation of chronic kidney disease.
A dog with kidney disease that suddenly develops large amounts of bloody diarrhea needs immediate veterinary evaluation because fluid loss can become serious.
Pancreatic or Other Systemic Disease
Pancreatic disease, liver disease, intestinal disease, and other systemic disorders can cause diarrhea.
Digestive signs can occur because of diseases outside the digestive tract, including kidney, liver, and adrenal disease.
Therefore, diarrhea in a dog with kidney disease should be interpreted in the context of the dog’s entire health rather than being automatically attributed to the kidneys.
Related: Old Dog Kidney Failure (Signs, stages and causes)
Dog Diarrhea and Kidney Disease but Still Eating
A dog with diarrhea and kidney disease may continue eating, particularly if the diarrhea is mild or caused by a relatively limited gastrointestinal problem.
Still eating is reassuring, but it does not completely rule out dehydration, worsening kidney function, or another medical problem.
If diarrhea continues, returns repeatedly, or is accompanied by weight loss, vomiting, increased thirst or urination, weakness, or changes in appetite, veterinary reassessment is appropriate.
Dog Diarrhea and Kidney Disease but Acting Normal
Some dogs with mild diarrhea continue to behave normally. This can happen with relatively minor gastrointestinal disturbances, but normal behavior does not identify the cause.
A dog with kidney disease may also have few outward signs during earlier stages. Early kidney disease can have no easily visible signs, while more advanced disease is associated with increasing systemic abnormalities.
For a dog already known to have kidney disease, persistent diarrhea is therefore worth reporting even if the dog still seems comfortable and active.
Dog Diarrhea and Kidney Disease With Vomiting
Diarrhea and vomiting together are more concerning because the dog can lose substantial amounts of fluid and electrolytes.
Advanced kidney disease can cause vomiting as waste products accumulate, but gastrointestinal disease, infection, dietary indiscretion, pancreatitis, and other conditions can also produce both vomiting and diarrhea.
Repeated vomiting and diarrhea can contribute to dehydration, which is particularly important in a dog whose kidney function is already impaired.
Dog Diarrhea and Kidney Disease With Blood
Blood in the stool can occur with several gastrointestinal conditions, including inflammation of the large intestine and acute hemorrhagic diarrhea syndrome.
The appearance of the blood can provide clues: bright red blood often comes from the lower digestive tract, while black, tarry stool can indicate bleeding higher in the digestive tract.
Blood in the stool should not automatically be attributed to kidney disease. A dog with kidney disease and bloody diarrhea should be evaluated, particularly if the diarrhea is frequent, severe, or accompanied by vomiting, weakness, or poor appetite.
Dog Diarrhea and Kidney Disease With Weight Loss
Weight loss can occur with advanced kidney disease as appetite decreases and systemic illness develops. It can also result from chronic gastrointestinal disease, malabsorption, parasites, or other conditions.
If a dog with kidney disease is losing weight while experiencing recurring diarrhea, the veterinarian may need to determine whether the kidney disease is progressing or whether an additional digestive disorder is present.
When to Call or Visit the Vet
Contact your veterinarian if a dog with known or suspected kidney disease develops diarrhea, particularly if it:
Persists or repeatedly returns
Is accompanied by vomiting
Contains blood or becomes black and tarry
Causes a noticeable loss of appetite
Is accompanied by increased weakness or lethargy
Occurs with weight loss
Is accompanied by significant thirst or changes in urination
Produces signs of dehydration
Occurs with abdominal pain or swelling
Is severe or very frequent
Develops soon after a medication change
Occurs in a dog whose kidney blood tests have recently worsened
Immediate veterinary attention is especially important when diarrhea is severe or bloody, vomiting is repeated, the dog cannot keep water down, marked weakness or collapse develops, or dehydration is suspected.
Acute severe diarrhea can cause substantial fluid loss, while kidney disease can make fluid and electrolyte management more complicated.
Dog Diarrhea and Kidney Disease: Treatment
Treatment depends on whether the diarrhea is caused by kidney disease, a separate gastrointestinal condition, medication, infection, parasites, or another problem.
The veterinarian may review the dog’s kidney history and current medications and perform a physical examination focused on hydration, abdominal findings, weight, and overall condition.
Bloodwork can help assess kidney function, electrolytes, hydration-related changes, and other abnormalities, while urinalysis and fecal testing may be appropriate depending on the history.
Additional abdominal imaging or gastrointestinal testing may be recommended for persistent or unexplained diarrhea.
Treatment is directed at the underlying diagnosis while carefully managing fluid and electrolyte balance; dogs with kidney disease may require particular caution when hydration and fluid therapy are being considered.
Key Takeaway
Dog diarrhea and kidney disease can be related, particularly in advanced kidney disease, when the buildup of waste products and other systemic effects can contribute to gastrointestinal signs. Merck lists diarrhea among the signs that may occur in severe stage IV chronic kidney disease.
However, diarrhea in a dog with kidney disease does not automatically mean the kidney disease is worsening.
Gastrointestinal infections, parasites, dietary problems, chronic intestinal disease, medication effects, and other conditions can cause diarrhea independently.
Because diarrhea causes fluid and electrolyte losses, persistent or severe diarrhea deserves particular attention in a dog with kidney disease.
Veterinary testing can help determine whether the kidneys are contributing to the problem or whether a separate gastrointestinal condition needs treatment.
