Bladder stones (uroliths or cystic calculi) are rock-like formations of minerals that develop in the urinary bladder. There may be a large, single stone or a collection of stones that range in size from sand-like grains to gravel. It is common for a mixture of both small and large stones to be present. There are at least 4 types of different stones, struvite, urate, cystine and calcium oxalate bladder stones.
The most common signs that a dog has bladder stones are hematuria (blood in the urine) and dysuria (straining to urinate). Hematuria occurs because the stones rub against the bladder wall, irritating and damaging the tissue and causing bleeding. Dysuria may result from inflammation and swelling of the bladder walls or the urethra, from muscle spasms, or due to a physical obstruction to urine flow caused by the presence of the stones.
Large stones may act almost like a valve or stopcock, causing an intermittent or partial obstruction at the neck of the bladder, the point where the bladder attaches to the urethra. Small stones may flow with the urine into the urethra where they can become lodged and cause an obstruction. If an obstruction occurs, the bladder cannot be emptied fully; if the obstruction is complete, the dog will not be able to urinate at all. If the obstruction is not relieved, the bladder may rupture. A complete obstruction is potentially life threatening and requires immediate emergency treatment. A urinary obstruction will usually be recognized in a dog that is straining to urinate without producing any urine, or is only producing small squirts of urine.
The symptoms of bladder stones are similar to those of an uncomplicated bladder infection or cystitis. Most dogs that have a bladder infection do not have bladder stones. Therefore, we do not conclude that a dog has bladder stones based only on these common clinical signs.
Some bladder stones can be palpated (felt with the fingers) through the abdominal wall. However, failure to palpate them does not rule them out. Some stones are too small to be felt in this manner, or the bladder may be too inflamed and painful to allow palpation.
Most bladder stones are visible on radiographs (x-rays) or an ultrasonic bladder examination. Some bladder stones are radiolucent, or are not visible on radiographs because their mineral composition does not reflect x-ray beams. They can be detected by an ultrasound examination
In general, there are three main treatment options for bladder stones: 1) surgical removal;
2) non-surgical removal by urohydropropulsion, and 3) dietary dissolution. The specific treatment that is recommended for your dog will depend on the type of stone that is present.
Option 1: Surgical removal of bladder stones. This is often the quickest way of treating bladder stones; however, it may not be the best option for patients that have other health concerns, or in whom general anesthesia could be risky. With this option, the stones are
removed via a cystotomy, which means that the bladder is surgically exposed and opened so that the stones can be removed. This surgery is routinely performed by many veterinarians and dogs usually make a rapid post-operative recovery. If the stones have obstructed the urethra, so that the dog is unable to urinate, an emergency procedure must be performed IMMEDIATELY to save the dog’s life.
Option 2: Non-surgical removal. If the bladder stones are very small it may be possible to pass a special catheter into the bladder and then flush the stones out, using a technique called urohydropropulsion. In some cases, this procedure may be performed with the dog under heavy sedation, although general anesthesia is often necessary. If your veterinarian has a cystoscope, small stones in the bladder can sometimes be removed with this instrument, thus avoiding the need to cut the abdomen and bladder open. Either of these procedures may be used to obtain a sample stone for analysis so that your veterinarian can determine if dietary dissolution is feasible.
Option 3: Dietary dissolution. In some cases, bladder stones can be dissolved by feeding the dog a special diet that is formulated to dissolve bladder stone(s). This diet will be tailored to the specific type of stone that is present. The advantage of this option is that it avoids surgery. It can be a very good choice for some dogs. However, it has three disadvantages:
It is not successful for all types of stones. Stone analysis is necessary to determine if it is the type of stone that can be successfully dissolved. This may not be possible in all cases. Sometimes, your veterinarian will make an educated guess on the type of stone, based on the radiographic appearance and the results of a urinalysis.
It is slow. It may take several weeks or a few months to dissolve a large stone so the dog may continue to have hematuria, dysuria, and recurrent infections during that time. The risk of urethral obstruction remains high during this period.
Not all dogs will eat the special diet. These diets will not work unless they are fed exclusively. This means that NO TREATS or supplements can be given to your dog while it is on the special diet.
Prevention is possible in some cases, depending on the chemical composition of the stones. Whenever possible, bladder stones (either those that are removed surgically or those small ones that have been passed in the urine), should be analyzed for their chemical composition. This will permit your veterinarian to determine if a special diet will be helpful in preventing recurrence. If the stones formed because of a bacterial infection, it is recommended that periodic urinalyses and urine cultures be performed to detect sub-clinical recurrences and determine if antibiotics should be prescribed. Periodic bladder x-rays or ultrasounds may be helpful in some cases to determine if bladder stones are recurring.