Dog Bladder Stones: Causes and Treatment

Introduction: If your dog urinates often or strains while going, or if he starts having accidents in the house, he may have bladder stones. If this is the case, you may sometimes also see some blood in his urine. This condition, called urolithiasis, occurs when many small stones or sometimes just a single stone, takes up space in the bladder, leaving less room for urine. Sometimes bladder stones can completely fill the bladder, causing the dog serious problems. Bladder stones may also cause your dog to seem less energetic and maybe just a bit “off”. Because stones develop when minerals in the urine crystallize and precipitate, the first step in diagnosis bladder stones will be a urinalysis by your vet, who will check your dog’s urine for the presence of crystals and other factors like pH – more about this below. Also, because almost all bladder stones are radio-opaque, they will usually be detectable on an X-ray which is the definitive test for the presence of the stones. The treatment of choice for bladder stones depends on knowing what type of stone is present, and here is where it gets a little tricky.
Causes: There are several different types of bladder stones, depending on their mineral composition, and which type of stone forms depends mostly on the underlying cause. To understand this, it’s important to keep in mind that urine is normally quite acidic. Neutral solutions, that is, those that are neither acidic or alkaline such as good-quality water, have a pH of around 7. The pH of an acid is lower than 7 and that of an alkaline or basic solution is higher than 7. The pH scale is a “log” scale, like the Richter scale for earthquakes, meaning that an increase (or decrease) of one point is ten-fold different than the previous point. So a pH of 6 is 10 times more acidic than a pH of 7. The pH of normal urine is usually around 5 and most common minerals found in urine like Magnesium, Phosphate and Calcium stay dissolved at this pH. However, when a bacterial infection develops in the urinary tract, one of the things that usually happens is the pH of the urine rises – it becomes more alkaline – due to the activity of the bacteria. As a result, the minerals normally dissolved in urine will crystallize or precipitate and, if this situation lasts for awhile, the crystals will combine into stones which grow too big to pass through the urethra. The result is bladder stones. The most common stones which form this way in alkaline urine are called “struvite” stones, composed of Magnesium-Ammonium-Phosphate, with perhaps a little Calcium. These stones only form in alkaline urine which is usually the result of an infection. The other type of stone that is less common but still seen pretty often is made of Calcium Oxalate. The big difference in oxalate stones compared to struvite is the cause – oxalate stones only form in urine that is acid, that is, of normal pH, and the cause varies. It can be genetic, or diet-related due to feeding high amounts of certain fruits and vegetables, dairy products or vitamin C, or it can have a metabolic cause such as Cushing’s Disease. There are other types of stones, but these are quite rare. Most stones fall into one of these two categories, struvite or oxalate, and just as the cause is different for each, so may be the treatment.
Treatment: There are several ways to treat bladder stones and the choice can depend on knowing or suspecting the type of stone. If the dog’s urine was alkaline and contained bacteria at the time of analysis, chances are the stones are struvite. In that case, the vet will treat with antibiotics and probably recommend a special diet that will dissolve the stones in a month or two. Checking the stones on Xray after a few weeks on the diet will show if they have gotten smaller and fewer in number and, if you have patience, the stones will eventually dissolve. If the urine was acidic when tested, the stones are not struvite and may be oxalate. In that case, surgical removal may be the best option. Although there is risk, the surgery is a common procedure and post dogs do well. Prevention of recurrence can be a challenge but there are good options to the sure that they don’t re-form. Vigilance in preventing urinary tract infections or in treating as soon as symptoms appear is a good first step. You may also want to add a daily capsule of cranberry concentrate to your dog’s food, since cranberry inhibits bacteria from attaching to the bladder lining. If the stones were oxalate, then the underlying cause needs to be identified and addresses. There are also newer diets such as S/O from Royal Canin that are nutritious and prevent formation of almost all types of stones in canine urine. *
*as published on examiner.com


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