Urolithiasis in dogs: causes of the formation of urinary stones, diagnosis and treatment

Dogs, unlike cats, rarely use a tray for sending their natural needs: as a rule, they do this exclusively on the street. That's why there are situations when diseases of the genitourinary system in these animals for a long time go unnoticed by the owners of the pet. And that's bad. We omit the "simple" cystitis, although even they can lead to major problems. What is worse is urolithiasis in dogs. This pathology in advanced cases begins to cause unbearable suffering to the dog. Alas, pets are usually taken to the veterinarian precisely during this period, when only immediate surgery can alleviate the condition of the animal. However, first things first.

General information

If you collect the urine of any animal in a container and leave it for two or three days, you can see some sediment at the bottom of the tank. This is normal: this is how salts, epithelial cells and other "waste" originally dissolved in urine settle. While urine is in the bladder, this does not occur under normal conditions.

If a precipitate begins to form already in the body cavity, this also should not always be considered a pathology. A small amount of it will not be able to bring any harm to the body of the animal. Problems begin when substances that contribute to the accelerated precipitation of salt crystals enter the urine. When this process is sufficiently activated, the formation of not just a precipitate, but crystals begins. The latter are called uroliths. Literally, their name can be translated as "urinary stones." It is this pathology that is called urolithiasis.

It is believed that from 2 to 10% of any urinary stone is an organic matrix (epithelial remnants and other organics). The remaining 90-98% accounts for the share of mineral components, the course of the disease and even its danger to the health and life of the animal largely depend on the chemical nature of them. Uroliths may appear in the kidneys, ureters, bladder, or urethra. The rate of their formation and size again depends on the chemical composition of calculi.

Determination of the nature of calculi

It is believed that in animals there are stones formed by about a dozen types of mineral compounds. Using a visual method to identify their origin is practically useless. Optical crystallography, infrared spectroscopy and / or using a method based on x-ray diffraction are much more reliable. But the problem also lies in the fact that dogs rarely have purebred uroliths: depending on nutritional characteristics, content and other factors, they can be composed of several varieties of chemical compounds. In such cases, it is necessary to use a stone core for analysis.

Why is this necessary? From the knowledge of the conditions under which the primary formation of calculi occurred, the subsequently prescribed treatment depends. In addition, on the basis of the same data, veterinary nutritionists will prescribe such a diet to the animal so that there are no relapses in the pathology.

"Mechanics" of stone formation

Until now, the mechanisms due to which the formation of uroliths in dogs are not fully understood. Today, experts adhere to three main theories of their occurrence:

  • Organic matrix. Proponents of this hypothesis believe that uroliths, regardless of their other features, can develop only under the condition of the formation of an organic matrix, a "skeleton" of protein nature, on which mineral compounds are subsequently deposited.
  • Crystallization Accelerators. This is a more common theory, whose "adherents" are of the opinion that a certain combination of substances is necessary, the combination of which starts and accelerates the crystallization of urinary compounds.
  • Crystalline Deposition Factors. Almost the same as in the previous case. What are the differences? Proponents of this theory suggest that some “special” substances are not required to start the crystallization process. They believe that a certain combination of substances that are occasionally found in the urine of every (even completely healthy) animal can lead to this outcome. This can happen, in particular, with a sharp change in the characteristics of the daily diet. However, if you constantly feed the dog with dry food, the same thing can happen.

Regardless of specific reasons, the formation of stones occurs only at certain concentrations of substances capable of forming a crystalline precipitate. If they are less than the crystallization threshold, the formation of stones will not occur, pathology cannot develop. For the formation of certain types of calculi (for example, struvites, cystines, urates), the coincidence of other, additional conditions is necessary. These may include an excessively low or high (relative to normal) pH level. These conditions can be caused by a urinary tract infection, diet, intestinal absorption, a drop in the daily volume of urine, a change in the frequency of urination, medications taken by the cat, and a genetic predisposition. In Persian cats, in particular, genetically determined pathologies of the kidneys are very common, which greatly contribute to the formation of stones in the organs of the genitourinary system.

Clinical picture

At first, when there is a small number of microscopic crystals in the kidneys, ureters, or bladder, there may not be any clinical signs. But sometimes, even in the initial stages of the disease, the animal already begins to feel unwell. This happens when the crystals appear on the mucous membrane of the ureters or accumulate in significant quantities directly in the renal pelvis. It ends with dysuria, hematuria and stranguria. As a rule, kidney stones do not manifest themselves in any way for a long time.

But it all ends as soon as the urolite breaks from its place and enters the lumen of the ureter. Since the diameter of the organ is small, its stone (as a rule) completely overlaps. Urinary tract obstruction has a severe effect on the pet's body due to developing intoxication. Vomiting, apathy, severe bouts of pain can be observed. Pain can be especially critical in cases where the pathology is accompanied by a stretching of the external capsule of the organ (kidney). The problem is that the pain in these cases is intermittent. It can suddenly appear and disappear just as quickly, and therefore the owners may not know that something is wrong with their pet's health.

Because of this, the disease continues to progress, remaining unnoticed. This can end extremely sadly: if there is no outflow of urine from the kidney, hydronephrosis develops. Consequently - the need for surgical removal of the affected organ. If the animal already had kidney problems, stones will only aggravate them. Unfortunately, not everything is so simple here. The kidneys are surprisingly tenacious organs. They are able to work normally when no more than 1/3 of the living cells remain. Therefore, in the early stages, signs of urolithiasis can occur in the following three cases:

  • Both ureters are pinched.
  • Exacerbation of an existing chronic kidney disease in an animal.
  • The development of infection due to the penetration of pathogenic or conditionally pathogenic microflora.


If we are talking about unilaterally located calculi in the ureters, they are sometimes accidentally discovered during routine examinations of the animal. The same goes for large stones in the bladder. With a deep palpation, it is quite possible to identify them. The detection of calculi is facilitated by thickening and coarsening of the bladder wall. Finally, animals with urolithiasis often "inadequately" respond to bladder palpation due to severe pain. Stones in the urethra are detected by the introduction of a catheter: if there are calculi in the organ cavity, it is almost impossible to put it inside the bladder.

Of course, all these research methods are only preliminary. Since small pebbles can be located throughout the urinary system, shown radiography. Most of the uroliths are impervious to x-rays, and therefore stones with a diameter of three millimeters or more are clearly visible in the pictures. But urate and, in some cases, cystine, can be permeable to x-rays. To detect them, contrast radiography is needed when the bladder or urethra is pre-filled with a contrast solution. But the task of the veterinarian is not only the visual identification of calculi. It is necessary to understand what is the general condition of a sick animal.

To do this, resort to microscopic examination of urine (small crystals are detected in this way), as well as for the placement of urine samples and scrapings of the urethra on nutrient media (in cases of suspected secondary infection). Finally, a chemical study of stones is shown, since only this method gives an accurate idea of ​​the nature of uroliths.

Therapeutic Techniques

What kind of urolithiasis in dogs is most common? This is struvite urolithiasis in dogs. When treating it, it is necessary that the urine pH drops to <6. This is achieved using a compiled by a veterinarian nutritionist diet, or using commercial feeds specially created for animals suffering from urolithiasis. It is believed that they need to reduce their daily intake of protein, phosphorus and magnesium, while increasing the sodium content in food. The measures taken stabilize the daily production of urine and significantly slow down the process of crystalline deposition. With a properly selected diet, the density and concentration of urine decreases, which also reduces the activity of bacteria that produce urease (an important cause of urolithiasis).

Important! During this period, it is strictly forbidden to give the dog any food with the exception of medicinal feeds. In this case, daily water consumption should not be cut. Dog access to water should be unhindered and around the clock. Otherwise, the treatment will be ineffective.

Besides, important treat secondary bacterial infections (if they develop). If there is such a possibility, antimicrobials should be prescribed only after determining the degree of their effect on a specific pathogen. Note that in the treatment of urinary tract infections, conventional amoxicillin has proven itself well. In addition, urease inhibitors are usually prescribed, but in practice this is not always required. In addition, drugs that regulate the production of this enzyme, with prolonged use, can contribute to the development of hemolytic anemia.

In more severe cases, only stone removal surgery can save the animal. (or their grinding by means of ultrasound). The decision should be made by the attending veterinarian.

Watch the video: Everything You Need to Know About Urinary Stones - Dr. Caronline Wallner, MD. UCLAMDChat (December 2019).