By Dr. A. Nichole Hooper, DVM
Acquired Fanconi Syndrome
Fanconi syndrome is a kidney defect that can result in loss of glucose, amino acids, bicarbonate, potassium and other molecules in the urine. Most documented reports of this form of kidney disease are those of dogs with inherited Fanconi syndrome. For example, Basenji dogs are one of the reported dog breeds that can be born with Fanconi syndrome. Until recently, acquired Fanconi syndrome was documented sparingly. However, over the last decade, reports of dogs with the acquired or idiopathic form of Fanconi syndrome have increased.
There are multiple causes of acquired Fanconi syndrome including kidney infection (i.e., Leptospirosis), medications (i.e., antibiotics, chemotherapy), liver disorders (i.e., copper storage disease) and chemical food additives. Based on the literature in dogs with acquired Fanconi syndrome, the majority of reports consist of toxins or drug reactions. Environmental toxins (i.e., lead, cadmium, mercury) accumulate in the food chain, leading to increased exposure in higher mammals. This ultimately results in renal tubular injury.
Acquired Fanconi syndrome has been reported in multiple breeds and occurs in dogs of all ages. Clinical signs of acquired Fanconi syndrome are not specific. Once kidney injury has occurred (i.e., by toxin or drug exposure), the dysfunction that ensues results in urinary loss of glucose, phosphate, sodium, uric acid, potassium and amino acids. Due to the lack of kidney reabsorption of these important nutrients, Fanconi syndrome is often referred to as a “wasting syndrome”.
The most frequently reported clinical signs in dogs with acquired Fanconi syndrome include increased thirst, increased urination, weakness, dehydration and weight loss.
In the most severely affected cases, death can occur due to renal failure and kidney necrosis or cell death.
Diagnosis of acquired Fanconi syndrome is based on a combination of clinical signs and lab work findings indicating kidney failure. Baseline lab work is ideally performed at presentation and should include the following: cell blood count, serum chemistry, blood gas and urinalysis. Dogs with Fanconi syndrome will have high amounts of the solutes normally reabsorbed by the kidneys in their urine (e.g., amino acids, proteins and glucose). One of the more common signs of Fanconi syndrome is high levels of glucose in the urine in the face of normal levels of glucose in the bloodstream (glucosuria with euglycemia). These patients will also exhibit metabolic acidosis (low blood pH due to loss of bicarbonate in the urine).
Urine amino acid measurements, urine culture and infectious disease testing to rule out other causes of renal failure are also recommended. Urine culture, Leptospira serovar titers, rickettsial (tick-borne disease) serology and diagnostic imaging (e.g. abdominal radiographs and ultrasound) are typically negative or within normal limits.
Once the index of suspicion for acquired Fanconi syndrome associated with diet has been established, affected dogs tend to benefit from early recognition and treatment. It is important to note, however, that once renal tubular damage has occurred, changes may not be reversible and treatment is largely supportive.
Supportive care for patients with acquired Fanconi syndrome is typically in the form of gastroprotectants, antibiotics and potassium and bicarbonate supplementation. Hospitalization for intravenous fluid therapy and intravenous supplementation may be indicated depending on severity of illness. A specific protocol has been published for Fanconi patients requiring long-term therapy. Overall, cases of uncomplicated idiopathic Fanconi syndrome appear to have normal life expectancies.
Consumption of chicken jerky treats made in China and associated illness in dogs have repeatedly made headlines. The U.S. Food and Drug Administration (FDA) released one of their first statements cautioning pet owners of a potential association between development of illness and consumption of chicken jerky treats in September 2007. In 2008, the FDA issued a Preliminary Animal Health Notification, but complaints about the products began to drop off between 2009 and 2010. These complaints started to increase again in 2011 and this prompted the FDA to release yet another cautionary update.
Illnesses reported are no longer associated with just chicken. Other jerky products, including those containing duck, beef and sweet potato have been implicated as well. Some food companies have voluntarily recalled their dog treat products. In response to consumer demand, a number of products are now made in the U.S. with U.S.-sourced ingredients. Sadly, and despite persistent safety fears, other pet food companies with tainted reputations continue to return their products to store shelves.
After an extensive seven-year investigation into the illness affecting thousands of pets that have consumed jerky treats, the FDA remains perplexed by the mysterious illness. To date, the FDA has not confirmed a causative agent, nor has one been specifically identified. Moreover, the illnesses and deaths reported have been associated with many different product brands. The FDA has partnered with the Center for Disease Control and Prevention (CDC) to begin an extensive study on what foods may be contributing to disease. However, the agency continues to appeal to pet owners and veterinarians to report jerky treat-related illnesses in hopes that an influx of information will ultimately lead to a solution.
About the author:
Nichole Hooper, DVM, earned her bachelor of arts degree in Zoology from the University of Florida in Gainesville, Florida. She then stayed at the University of Florida where she received her Doctorate of Veterinary Medicine in 2006. Following graduation, Dr. Nichole Hooper completed a rotating small animal medicine and surgery internship in Cooper City, Florida at Veterinary Specialists of South Florida from 2006-2007. She continued her specialty training with an emergency and critical care internship from 2007-2008. Dr. Nichole Hooper then completed an emergency and critical care medicine residency at Veterinary Specialists of South Florida in 2011.
Dr. Nichole Hooper’s special areas of interest include toxicology, trauma, wound management, sepsis and transfusion medicine. In November 2011, Dr. Nichole Hooper was published in the Journal of the American Animal Hospital Association on acquired Fanconi syndrome in dogs exposed to chicken jerky treats. In her free time, Dr. Nichole Hooper enjoys traveling, doing yoga and playing with her two Labrador retrievers.