Fanconi Syndrome in Dogs

By Laura Russell, DVM, MBA, DABVP on Jun. 20, 2023

What Is Fanconi Syndrome in Dogs?

Kidneys function to filter the blood. They remove waste products and control the flow of nutrients and fluids. Within the kidney, tiny tubules perform these tasks. Dogs have hundreds of thousands of them that keep glucose, amino acids, and electrolytes such as potassium and chloride in balance. Glucose and amino acids provide the energy needed to allow puppies to grow and keep dogs healthy. Electrolytes help control hydration, many metabolic processes, and keep the pH (acid-base status) of body tissues normal.

In dogs with Fanconi syndrome, these renal tubules are “leaky” and too much glucose, amino acids, and electrolytes are passed from the bloodstream into the urine. The leaking nutrients cause weight loss, muscle loss, and fatigue. Unbalanced electrolytes result in dehydration, weakness, and dangerous changes in the normal acid-base balance in the blood, known as pH.

Fanconi syndrome is a chronic but usually manageable disease. If the disease is undiagnosed, untreated, or progresses into renal failure, it can be fatal. Any severe clinical signs or worsening of symptoms should be considered a medical emergency.

Symptoms of Fanconi Syndrome in Dogs

Excessive urination
Extreme thirst/drinking
Weight loss
Decreased appetite
Poor body condition
Poor growth rates in young dogs
Weakness or extreme tiredness

Causes of Fanconi Syndrome in Dogs

Fanconi syndrome in dogs can be genetic. About 75 percent of dogs with Fanconi syndrome are Basenjis; it’s recommended to have genetic testing for this breed.

Fanconi syndrome can also be caused by:

Eating toxins (such as melamine, lead, copper, or salicylic acid)
Uncommon reactions or high doses of some medications
Concurrent diseases, such as hypoparathyroidism or low vitamin D

How Veterinarians Diagnose Fanconi Syndrome in Dogs

Veterinarians will start with a full physical exam and may recommend the following testing:

Complete blood count
Chemistry panel
Blood gases
Urinalysis
Urine sample testing for the concentration of amino acids in urine

Treatment of Fanconi Syndrome in Dogs

Fanconi syndrome does not have a cure, but it can be managed with a dietary supplement such as mineral or amino acid supplements. Depending on lab work, special diets to adjust the amount of protein in the food may be needed. It’s critical that dogs with Fanconi syndrome always have access to fresh water and that their health is closely monitored.

If Fanconi syndrome is severe or progresses into renal failure, your dog many need to be hospitalized for IV fluid and electrolyte therapy.

Recovery and Management of Fanconi Syndrome in Dogs

The life expectancy of dogs with Fanconi syndrome varies. Some dogs can be managed well for years, but others do not respond and can progress quickly into renal failure.

Dogs with Fanconi syndrome will benefit the most from careful monitoring by their families and their veterinarians. Dogs should always have fresh water available and be encouraged to drink frequently.

Any new symptoms, such as weakness, weight loss, vomiting, diarrhea, refusal to eat, or changes in urination need to be evaluated by your veterinarian.

Fanconi Syndrome in Dogs FAQs

What is "Fanconi-like Syndrome"?

This is a term used to explain dogs when they show the symptoms and test results of a dog with Fanconi syndrome but are not genetically predisposed to the disease. These dogs are usually identified as having been exposed to some sort of toxin.

In some cases, Fanconi-like syndrome was reported in dogs eating jerky treats made outside the United States. In the majority of these cases, the symptoms resolved once the toxin was removed from their diet, though the possibility of severe lasting kidney damage may still exist.