Fanconi Syndrome in Dogs
I have a Basenji puppy, and I am worried about a condition called Fanconi syndrome that I read about. I know it has to do with the kidneys, but I don’t understand the details. Is this something that my puppy will definitely develop?
The kidneys provide many critical functions in the body. They regulate fluid balance, filter toxins from the blood, excrete waste products, and balance the concentration of many different compounds in the body. Fanconi syndrome describes abnormal function in part of the kidneys called the tubules. The tubules should reabsorb water, electrolytes and nutrients as urine is formed that would otherwise be excreted in the urine, but that are critical to normal metabolic function. With this syndrome, the tubules do not properly reabsorb the electrolytes and nutrients, and instead ‘spill’ them back into the urine to be expelled. The electrolytes and nutrients that fail to be reabsorbed and are excreted in excess in Fanconi syndrome include:
- Glucose (sugar)
- Amino acids
Fanconi syndrome has been reported in several different dog breeds, but the vast majority of reported cases (75%) have occurred in Basenjis. Approximately 10 – 30% of Basenjis in North America are affected. Unfortunately, the precise mode of inheritance is not yet known.
Affected individuals may exhibit signs of Fanconi syndrome as early as 11 weeks of age, but typically clinical signs emerge from 4 – 7 years of age. Males and females are equally affected. Ultimately, kidney failure develops in these dogs.
What are the clinical signs of Fanconi syndrome? Is there a specific test for Fanconi syndrome?
The signs of Fanconi syndrome vary depending upon the severity of loss of specific nutrients, and whether or not kidney failure has developed. Dogs with Fanconi syndrome may lose weight despite eating normally. Excessive drinking and urinating are the most common clinical signs. As the disease progresses, these dogs develop poor body condition and may experience decreased appetite and lethargy. Uncommonly, very young dogs can develop Fanconi syndrome, and these dogs have abnormal bone development.
While there are no specific tests for Fanconi syndrome, diagnosis depends upon several factors. Basenjis who drink and urinate more than normal create a high index of suspicion. If there is glucose in the urine, but the level of glucose in the blood is normal, this is highly suspicious of Fanconi syndrome. In fact, this glucose disconnect is often the very first suggestion of Fanconi, preceding other clinical signs. About 1/3 of cases develop low blood potassium levels.
How is Fanconi syndrome treated?
There is no way to reverse the abnormal reabsorption of solutes that occurs in Fanconi syndrome. Management of this disease depends upon the severity of the reabsorption defects, so must be individualized to the specific patient. Treatment may include potassium supplementation, nutritional management of kidney disease, and support of normal acid-base balance in the body.
What is the expected outcome for dogs with Fanconi syndrome?
The clinical course of Fanconi syndrome varies, so it is important to measure specific blood tests every couple of weeks initially to assess the effects of treatments. Once the values are stable, these tests will be rechecked every two to four months. Some dogs remains stable for years, but others may develop rapidly progressing kidney failure over just a few months. Most dogs with Fanconi syndrome ultimately die of end-stage kidney failure. The variability among Fanconi patients emphasizes the need for regular ongoing monitoring of metabolic function via laboratory tests.
Many dogs with Fanconi syndrome do live close to a normal life expectancy. Your veterinarian will guide you as to when (or whether) it is appropriate to begin screening your dog for evidence of Fanconi syndrome.
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