Last week, it was mentioned that there are four basic problems which could affect the lower urinary tract. We dealt with the bladder infection (cystitis) and urinary retention (obstructed bladder). Today, we’ll deal with the emergence of bladder stones.
Bladder stones (urolithiasis)
The main function of the urinary system is the removal of waste matter from the body in liquid form. But it must first be understood that some mineral wastes are only slightly soluble and therefore they can form crystals. If the time taken for these crystals to move through the urinary system is prolonged, the chemicals in the crystals can react with one another and form stones (eoliths) anywhere.
You may wonder why we place emphasis on bladder stones and not kidney stones. It is true that in humans it is in the kidneys where stones are usually formed. Not so in dogs. In the many decades as a practising veterinarian, I had never encountered kidney stones – not even as a coincidental finding in a post mortem. In dogs (and cats), stones develop (or at least are found) in the bladder.
The formation of stones (as can be understood from some of the statements made above) will be influenced by (i) high concentrations of stone-forming chemicals (crystals) in the urine; (ii) the length of time the concentrated chemicals take to pass through the urinary system; and (iii) a favourable environment (pH) for crystal formation to take place.
Stones are of different types. Actually, they are often salts (chemical compounds that develop from acids and bases). According to the diet, the urine could be acid or alkali. So, if the urine produced has a lot of uric acid, say, the urate salts (stones) can develop. This is especially true for Dalmatians, which seem to be the only breed that can relatively easily form uric acid stones. Other stones are formed in alkaline urine. These latter conditions are often also associated with infections. Obviously, if the stone is grating constantly against the internal wall of the bladder, it will precipitate an inflammatory process in the bladder.
In terms of size and structure, there are varying types of stones that can accumulate in the bladder. Some stones are round; others are tetrahedral (four faced, pyramidal structure), etc. In fact, the shape of the stone can sometimes give an inkling as to which type of chemical compound is involved. Some stones are in the form of ‘gravel’ (small stones), while in other instances, there is only a single (or several) large stone(s).
The gravelly stones create great pain as they are voided from the bladder through the urethra (the tube leading from the bladder to the penis/vagina). The large stone will simply block the flow of the urine. In any event, the presence of stones rubbing against the internal bladder wall will surely create an inflammatory condition within the bladder (cystitis) –see TPC of June 10, 2012. Of course, if a cystitis already exists (for whatever causative reason), that condition could help create the environment for stones to develop.
Other conditions that could influence the formation of stones are diet, urinary tract infection, volume of urine, frequency of urination, genetics (we are told that the Pekinese, Dachshund and Cocker Spaniel breeds are especially prone to develop bladder stones).
The dog strains to pass urine; sometimes the urine is tinged with blood. The general abdominal area is painful to the touch; the dog is depressed and has an anxious look. An X-ray picture can be of great assistance in supporting the diagnosis relative to the presented symptoms.
The therapy regime should be directed at creating a chemical environment (blood, urine) that is not conducive to the formation of stones (maintaining acidic urine), and ensuring that the urine volume is such that the small crystals are not easily formed. If it is possible, one should try to ascertain (via a recognized laboratory) the chemical composition of the stone, and it is always good to carry out a urine analysis.
There are two methods to deal with the formed stones:
(1) Dissolve the stones
(2) Surgically remove the stones
Relative to the dissolution protocol, there are commercially available rations (feeds) that can help in this regard. No snack should be fed, and water must be available at all times. Any existing urinary tract infection must be treated. The ‘stone dissolution’ method can be quite costly. Once I see the stones in the X-ray, I advise the surgical approach. Let’s get rid of the problem, then take the steps (diet, etc) to prevent the recurrence.
Next week, we’ll deal with urinary incontinence and urethral obstruction.