Bladder Stones (Urolithiasis) Part 1

This is a condition frequently seen in dogs and cats and in both males and females. Stones can develop anywhere in the urinary tract: the ureters ( 2 small tubes that carry urine from the kidneys to the bladder), the bladder which stores the urine, and the urethra which takes the urine  from the bladder to outside the body. Over 85% of the times,  stones develop in the bladder. (Very rarely do stones develop in the kidney in dogs and cats, called renal calculi.  Humans get renal calculi and not bladder stones.) In dogs and cats, certain minerals can precipitate out of the urine and become a sandy particle,  more can develop and when they cling to each other a calculus (urolith, stone) develops. They can become 3-4” in diameter and can take up to 99% of a bladder. The largest one I every removed was the size of a goose egg and it took up the majority of the bladder. It was in a female standard poodle. Most stones develop as the result of a bladder infection known as cystitis. Diet is involved as the diet influences the ph (level of acidity) and the mineral content of the urine. Water is involved because if the urine is very concentrated from lack of water consumption, more precipitates occur.  And the breed is involved because certain breeds are predisposed to calculi development. These breeds include: Schnauzers, Lhasas, Yorkies, Bichons, Shihtsus, and mini Poodles.  In male dogs and cats, the urethra is long and narrows at the penis where stones can get stuck and cause a complete obstruction. This obstruction must be relieved, urine must flow, or else it can become fatal. The stones can get stuck near the neck of the bladder, or by the prostate as it narrows going through,   midway down the urethra where it curves, or just behind the penis, (dogs have a bone in the penis known as the os penis, and the urethra is very small there). Early signs of bladder stones are the same as cystitis: frequent urination of small quantities, blood in the urine, urinary accidents, and apparent straining to urinate. The worse sign is attempting to urine but nothing comes out.  Occasionally the bladder stones can be felt with gentle palpation of the lower abdomen, and often a urinalysis shows crystals in the urine which are the precursors of calculi, but usually x-rays are taken to confirm the diagnosis.  If  crystals show up in the urinalysis, and even if very small calculi are present, surgery is sometimes avoided by just changing the diet, especially in females. Small stones in males are the most dangerous ones because of the obstruction possibility.

Bladder Stones (Urolithiasis) Part 2

Last week I discussed what these stones are and how common they are found in dogs and cats. Bladder stones are formed by minerals, which first precipitate out in the urine as separate microscopic crystals. The most useful diagnostic test used is the urinalysis. Many times these crystals show up in the microscopic analysis of urine and an early diagnosis of the potential of calculi development is determined. The most common type of stone is struvite. These stones are made up of magnesium ammonium phosphate. Other stones are made up of calcium oxalate, calcium phosphate, cystine, ammonium urate, etc. Some stones are a composite of more than one type. This reinforces the importance of a urinalysis, because the treatment varies with the chemical makeup of the crystals. Also, it is very important to determine if an infection is present, as well as the urine pH (level of acidity). Radiographs must be taken to determine the presence of the larger aggregates of minerals called calculi, and their size and location. In males, the size and location of these stones will indicate the risk of obstruction, while in females the small stones in the bladder or urethra can actually pass through the urethra to the outside. One the diagnosis is made, the size and location determined, a decision is made to try or not to try to reduce the size of the stone by means of diet and medication. Sometimes medical therapy is used in conjunction with surgery to treat the patient and eliminate the problem. In males the obstruction potential always looms, so usually surgery is the best choice. The usual associated infection is treated, as well as the correction of pH. The surgical procedure is known as a cytology (my favorite operation). If all the stones are located in the bladder only, and none lodged in the urethra further down the urinary tract, the procedure is very successful, with a quick recovery When the urethra is involved, although the procedure is also very successful, it is more involved, and recovery is longer. Once the immediate problem is resolved, whether by surgery or medical management, the prevention now is the key. We now know that this pet has the genetic capacity of stone production. The type of stone determines which food is recommended to prevent future stones from developing. For instance, struvite producing dogs require a completely different type of food than urate producing dogs. Keeping your pet on the special food is an absolute must. Otherwise, stones will reoccur and surgery has to be repeated. Frequent urine microscopic analysis is very important to determine if any crystals are beginning to form again. Next week my article will be Urolithiasis in Cats. To view more articles, go to my website at http://www.locustvalleyvet.com

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