Dogs with bladder stones may have blood in their urine and may urinate frequently, passing only small quantities of urine each time. Often, they will strain while urinating, holding their body in the urinating posture for much longer than normal. They may lick their genital area more than normal or may show signs of pain or discomfort when urinating. It is also common for dogs with bladder stones to have accidents within the home. Some dogs with bladder stones may show no signs at all, and the stones are discovered while palpating the abdomen during a routine physical exam. Urinary obstruction caused by calculi would cause much more severe clinical signs. These symptoms may include abdominal pain, firm and distended bladder, vomiting, dehydration, lethargy, and collapse.
Some stones are noted during palpation of the abdomen during a routine physical exam. In other cases, the diagnosis of bladder stones in dogs is made or confirmed with abdominal x-rays or ultrasound of the bladder. Most stones are radiopaque, meaning they show up on the radiographic film as obvious white objects within the urinary bladder. A few are radiolucent and they do not show up on x-rays. Radiolucent stones may require diagnosis using a contrast dye and x-ray or ultrasound.
There are several different types of bladder stones in dogs. Struvite stones are composed of magnesium, ammonium, and phosphate. Others are made of calcium oxalate, calcium phosphate, cystine, ammonium urate, or other chemical compounds. Some stones can actually be a combination of these. Each type of stone has its own different peculiarities as to which breed is most often affected and what factors affect the formation. See below for a summary.
Struvite: These stones typically form in alkaline urine. Treatment may include antibiotics for any urinary tract infection, a prescription diet to dissolve stones or surgery to remove them if indicated. Specific prescription diets that may dissolve struvites include Hill's s/d or
Royal Canin Urinary SO. Hill's c/d, w/d or Royal Canin Urinary SO are diets your veterinarian may recommend for prevention.
Oxalate: These stones typically form in acidic urine that is high in calcium, citrates or oxalates. Treatment typically requires surgery to remove them or urohydropropulsion if stones are very small. Oxalates cannot be dissolved using a special diet. Hill's u/d, Royal Canin Urinary SO or Purina NF Kidney Function may be prescribed by your veterinarian to prevent oxalate crystal or stone formation in susceptible dogs. If Hill's u/d is used long-term, your veterinarian should monitor your dog for signs of protein depletion.
Urate: These stones form more frequently in Dalmatians and Bulldogs as well as a result of certain liver related conditions. Once liver disease has been ruled out in breeds urate formation is not frequently seen in, treatment may include a special diet along with medication,such as allopurinol, which can be dispensed by your veterinarian. If there is liver disease or an obstruction, surgical removal of stones may be recommended. Urates can only be dissolved using a special diet if they are pure, although they are often a combination of different substances. Hill's u/d, or Royal Canin Vegetarian may be recommended by your vet to prevent urate crystal or stone formation in susceptible dogs. If Hill's u/d is used long-term, your veterinarian should monitor your dog for signs of protein depletion.
Cystine: These stones form more frequently in acidic urine and in dogs with the SLC3A1 gene mutation. Treatment may include Hill's u/d diet, Potassium citrate and 2-Mercatopropionylglycine if there is no obstruction present. Cystine crystals or stones may be dissolved using Hill's u/d diet. In some breeds cystine stone development has been linked to testosterone, and neutering is thought to be curative of the disease in Cystinuria Type III.
With all diets, it is extremely beneficial to also increase the amount of water consumption.
Bladder stones are formed by minerals, which first precipitate out in the urine as individual microscopic crystals. Over time, these crystals unite and small grains of sand-like material may be formed. Once these grains are present, additional precipitates form on their surface and the tiny specks are gradually built into stones that sometimes reach 3" to 4" in diameter.
The process by which bladder stones develop is really quite simple, but what causes it to occur only in certain dogs, cats, or humans? Factors that influence the development of stones include genetic predisposition, the concentration of the stone constituents in the urine, urine pH, and the presence of bacterial infections.
Genetics: The genetically controlled physiology of some animals causes them to produce higher levels of substances that are precursors of crystals. These substances are then excreted or formed in the urine.
Concentration of stone constituents: When there are more building blocks to create urinary bladder stones, then there is a higher likelihood of forming the stones. The concentration of these building blocks can be influenced by the amount of minerals and protein in the diet, the amount of water the animal drinks, and the animal's unique metabolism.
Urine pH: The acidity or alkalinity of the urine influences whether the stone constituents will remain dissolved or form stones. Some stones, such as struvite, form in alkaline urine, whereas others, including calcium oxalate stones, are more apt to form in acidic urine. The urine pH is largely influenced by diet, however, infection and metabolic disease can affect pH as well.
Bacterial Infections: Bacterial infections of the bladder (referred to as cystitis) play the major role in struvite stone information for two reasons.
Bacterial infections tend to make the urine more alkaline (with a pH higher than 7.0) which enhances the formation of struvite crystals. If the pH can stay lower than 7.0, then the struvite crystals are more likely to remain dissolved in the urine and no crystals would form.
Many of the bacteria that cause cystitis also produce an enzyme called urease. Urease reacts with urea molecules found in the urine to form ammonia and carbon dioxide. The ammonia is slowly converted to ammonium ions, while the carbon dioxide unites with other compounds, freeing up phosphates. Then, through a chain of chemical reactions that seem to feed on each other, the magnesium that is normally present within the urine unites with the ammonium and phosphate to form magnesium ammonium phosphate crystals (struvite). If the crystals are formed rapidly and in large quantities, they will unite together to form stones. However, if only small amounts are formed over a longer period of time, they may simply be flushed out in the urine without causing any noticeable problems.
Treatment costs may vary greatly depending upon the size of the patient, severity of the condition and the method of treatment. Conservative treatment with diet and medication will vary based on patient size and length of treatment. Prescription diets can range between $40 and $80 per case or bag for canned or dry diets. Antibiotics may cost between $50 and $100. Urohydropropulsion, including sedation, typically cost between $400 and $800. Laser lithotripsy may range between $800 and $1500. The cost for a cystotomy surgery may start at around $1500 for a small dog and $2000 or more for larger breeds. These costs are broad estimates. Most clinics will provide an estimate for services, when requested, as a matter of hospital policy.
The recovery period will depend on both the size and type of stones present. Surgical and medical treatments will result in a faster recovery time. Dietary dissolution is slower and can take several weeks to a few months to dissolve a large stone. During this time the dog may continue to have hematuria, dysuria, and recurrent infections. In addition, urethral obstruction risk remains high before the stone is completely dissolved. If your dog underwent any type of surgical procedure for stone removal, be sure to restrict exercise and have your veterinarian fit your dog with a surgical cone to allow proper healing of the surgical site.
Routine monitoring may include bloodwork, urinalysis, x-rays, and/or ultrasound. Close monitoring for return of clinical symptoms is very important and would indicate a return trip to the veterinarian immediately.
Diet plays an important role in preventing recurrence of some stones. Prescription diets have been formulated to reduce the reformation of struvite, calcium oxalate, urate, and some types of cystine crystals. Encouraging an increase in water intake is also important since many forms of crystals are less likely to form in dilute urine.
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