Xanthine Urinary Tract Stones in Dogs

Xanthinuria results in an excessive amount of xanthine in the urine. Xanthine is a compound that works in metabolizing proteins throughout the major organs of the body including the liver, pancreas, and spleen. Xanthine works by processing and breaking down urates (salts) with the enzyme xanthine oxidase. Xanthine works as a digestive product ridding wastes, with specific enzymes to be transformed into uric acid to be discarded in the urine. When enzymes become deficient it increases the risk of forming xanthine stones in the kidneys, urethra, or bladder, where obstruction or total blockage can take place, leading to rupture.

Xanthinuria can either be a congenital or acquired disorder, and is due to the presence of excessive xanthines present in the urine. Consuming foods that are rich in purines can contribute substantially to this condition as can highly concentrated urine, and an inherited deficiency of the enzyme xanthine oxidase.

• Pain
• Development of urolith calculi
• Hematuria (blood in the urine)
• Yellow-brownish urine
• Frequent urination
• Release of small amounts of urine
• Acute or chronic kidney failure will lead to worsening symptoms
• End-stage renal failure can cause collapse
• Death

Types

Xanthine urinary tract stones can be a hereditary disease which leads to the  excessive excretion of xanthine within the urinary tract. It is a very rare disorder, constituting only up to 1% of all known urinary tract calculi. Hereditary xanthinuria is known to be most prevalent in the breeds of Cavalier King Charles Spaniel and Dachshunds.

Type 1 Xanthuria

• Lack of the Dehydrogenase oxidase enzyme

Type 2 Xanthuria

• Lack of dehydrogenase enzyme
• Lack of sulfate 
• Lack of aldehyde oxidase

Xanthine stones can also be an accumulated and acquired condition resulting from the excessive use of Allopurinol medication, known to be a structured isomer medication to inhibit the xanthine oxidase enzyme.

• The Cavalier King Charles Spaniel is prone to xanthine urinary tract stones
• Documentation has been recorded in the Dachshund also
• Diets high in purine (meats such as bacon, liver, kidney and seafood) can cause an elevated amount of uric acid levels in the body
• Kidney problems can lead to an excessive amount of accumulated uric acid that must be stored, distributed, and deposited elsewhere leading to crystal formation
• Purine Foods are digested and metabolized into hypoxanthines, which are transformed into xanthines, and converted into uric acids and then disposed of in the urine

If you see that your canine companion is having trouble urinating or is releasing only small quantities of urine at a time, a visit to the clinic is essential. Your pet may not be clearly exhibiting the true amount of pain that he is experiencing. Dogs can be very stoic in this regard and may show small behavioral changes that mean more than you know. Discuss with the veterinarian all signs of discomfort and demeanor changes that are not normal. Any information you can provide will aid in the diagnostic process. Recent illnesses, medications, and injuries are all relevant pieces of information to relay. The veterinarian will perform a physical examination on your pet that will include vital signs and palpation of the abdomen. Standard testing will include complete blood count and serum biochemistry. The blood enzymes will also be analyzed. A urinalysis may reveal crystal or sedimentation in the urine; further testing such as high pressure liquid chromatography can determine hypoxathine and xanthine excretion in the urine. More extensive diagnostic tools may include the use of an ultrasound to view the bladder and the kidneys which also analyzes the urethra and bladder, as well as intravenous pyelography (contrasting the ureters and the kidneys), useful in locating the exact location and size of the xanthine calculi within the kidney and urinary tracts.

Dietary Management with Water 

Maintaining your dog’s diet is an effective way to dissolve the stones as well as prevent recurrence. The most important component to prevent highly concentrated levels of purines is to ensure ample amounts of liquid. Be sure that your dog has access to clean, fresh water. There are special diet foods provide ingredients low in purines. When feeding your dog avoid foods containing seafood, bacon, and liver.  

Discontinue use of Allopurinol

 Many veterinarians may treat the symptoms of pain and renal failure with the use of other medications.

Voiding Urohydropulsion

This procedure has the ability to remove smaller stones without the use of surgery.  While your dog is sedated, your veterinarian will use a catheter to fill the bladder with a sterile saline solution, which is compressed to excrete the stones out through the urethra.  It cannot be used for removal of stones stuck in the kidneys or ureters.

Surgery

In severe cases, surgery may be needed to remove large calculi lodged or stuck within the ureters or lower intestinal tract.

If your pet had surgery, you will need to provide a quiet, restful place for him to rest and recover when he is released from the care of the veterinary team. Your veterinarian will give you instructions for home care, to be followed carefully. You will need to bring your dog to the clinic for follow-up visits to see if dietary management is working. Recurrence of urinary tract stones  is possible so be sure to be vigilant in monitoring your pet closely and carefully for signs of renal disease or failure. Your veterinarian will also want to schedule routine urinalysis to check for abnormalities.