What Causes Crystals in a Maltese's Urine?

Maltese dogs can sometimes develop crystals in their urine. These crystals clump inside the bladder or the kidneys and form painful stones that make it difficult for the dog to urinate. Maltese dogs are genetically predisposed to a serious and potentially life-threatening disorder called a portosystemic liver shunt. Urinary crystals are a symptom of this condition.

  1. Portosystemic Liver Shunt

    • According to the University of Tennessee Institute of Agriculture, fetal mammals do not need their livers to filter out toxins. The mother's liver does all the work. The puppy's blood passes around the liver without cleaning it through a large blood vessel called a shunt. The shunt is supposed to shut down shortly before birth as the puppy's liver begins to work. However, in many cases the shunt does not close. The puppy is born with a condition where the liver does not filter out the toxins from the bloodstream. This condition is called a congenital portosystemic shunt.

    Symptoms of a Liver Shunt

    • In a 1998 article by Jay Bianco, writer for the Maltese Only website, most Maltese dogs with portosystemic shunts develop ammonium urate crystals or stones in the urinary tract. This happens because the liver is not able to filter out ammonia from the body. Some other symptoms of a liver shunt not closed are slow growth rates in puppies, vomiting, drooling, a lack of appetite, blindness and seizures.

    High-Risk Groups

    • The University of Tennessee Institute of Agriculture indicates that the Maltese breed is at high risk for being born with extrahepatic shunts, or shunts that form outside the liver. Some other small-breed dogs that may develop the condition are schnauzers, shih tzus, poodles and Jack Russell terriers. The condition often becomes apparent after surgery. Dogs with liver shunts do not eliminate the anesthetic but keep cycling it through their bodies.

    Diagnosis and Treatment

    • A veterinarian may suspect that a dog has a congenital portosystemic shunt based upon the predisposition of the breed and the age of the dog. According to the Canine Inherited Disorders Database, the doctor injects a high-contrast dye into the dog's bloodstream and uses radiography to track its progress through the body to see whether the blood goes to the liver. He may also perform bloodwork and a urinalysis.

      Symptoms of portosystemic shunt can be treated by limiting the amount of ammonia that the dog takes into its body. A low-protein diet with a limited amount of meat will improve the symptoms. However, the condition usually requires surgical intervention to close off the shunt. The Canine Inherited Disorders Database strongly recommends having dogs spayed or neutered if they show signs of this disorder so that the disease does not get passed down to the animal's offspring.