Urolithiasis (ICD) of cats and cats. Feeding, prevention, treatment

A well-groomed and properly fed cat, which is under the constant supervision of a veterinarian, is usually healthy. But just like humans and all other living beings, cats are prone to various diseases. Of course, it is impossible to give comprehensive information about all feline diseases, but cat owners need to know the main signs, manifestations and treatment of at least the most common diseases in this type of animal.

Urolithiasis affects from 1 to 13.5% of cats. This is one of the diseases of cats, which is characterized by very significant differences in views on the etiology and causes of occurrence. Urolithiasis is one of the most common pathologies observed in cats, accompanied by the formation of sand and stones in the bladder (not in the kidneys!). Due to anatomical features, cats suffer from this disease much more often than cats. The disease usually first appears between the ages of 2 and 6 years.

Historical reference

For the first time, they started talking about urolithiasis in the 70s of the twentieth century. In 1973 a group of researchers proposed a viral cause of the origin of urolithiasis. The role was assigned to calicivirus and herpesvirus infection of cats. This assumption has not been confirmed in numerous other studies. In the 1970s, it began to be assumed that the use of dry foods or their mixing could lead to urolithiasis. Scientists have proven that this is not the case, although the important role of magnesium salts in the occurrence of urolithiasis has been established.

It has now been established that insufficient water intake in the body of a cat and an increased pH value of urine contribute to the formation of uroliths and the occurrence of urolithiasis.

It has evolved so that cats have a weakened sense of thirst. Cats are descended from the African wild cat, and they have retained the body's ability to concentrate urine, which, accordingly, can contribute to the formation of stones - struvites (the main uroliths in urolithiasis).

Urine and its role in the cat's body

Urine plays a fundamental role in the life of cats. Its main role is to remove residual waste products of the body and toxins that accumulate in the bloodstream. Urea is excreted in the urine (hence its name) and other products, such as uric acid, creatinine, sodium, oxalates. In addition, urine plays a role in maintaining homeostasis by regulating the excretion of water and minerals from the body. Urine formed in the kidneys as a result of filtering blood through the nephrons, flows down the two ureters and accumulates in the bladder. When the animal feels the urge to urinate, the urine is expelled through the urethra.

Unlike humans, cats have a bone in their penis. With urolithiasis, the bone of the penis serves as an obstacle to the removal of stones, and most often it is in this place that the blockage of the urethra occurs.

Causes

By and large, scientists have not yet reliably determined what can be the cause of urolithiasis in cats. It is assumed that in most cases the formation of urinary stones is caused by a violation of water-salt metabolism as a result of improper, monotonous feeding and vitamin deficiencies. There is also an opinion that the constant feeding of commercial dry food is one of the leading factors that leads to the formation of stones. And, often when examining animals, the owners admit that they basically, and often constantly feed their pets with just such feeds. And, the latter are usually supersaturated with phosphates (bone meal), the main substances contributing to the onset of the disease.

In addition to the monotonous and improper feeding of concentrated feeds, there are other reasons that can directly or indirectly affect the formation of stones in the kidneys and urinary tract:

• microorganisms - staphylococci, streptococci, proteus and others;
• prolonged stagnation of urine - as a result, alkalization occurs, precipitation of salts and the formation of stones;
• medicines, namely their uncontrolled and too frequent use;
• polyhypovitominosis - insufficient intake of vitamins in the body;
• individual characteristics of the cat's body;
• climatic conditions (according to the same scientists, in Russia, for example, the disease is most often found in the North Caucasus, the Urals, the Don, the Volga. This is due to the characteristics of the soil, vegetation and water composition);
• violation of the functions of the endocrine organs - the thyroid gland, gonads, etc.;
• small diameter of the urethra, especially for neutered cats;
• inflammatory processes in the renal pelvis, urinary tract, bladder.

Symptoms

The manifestation of the disease directly depends on where the urinary stones are located, as well as on their size, the nature of the surface and mobility. The main signs of urolithiasis in cats include:

• pain during urination, which is manifested by the anxiety of the animal when visiting the toilet, a tense posture, as well as plaintive sounds;
• frequent urination;
• hematuria, that is, the appearance of blood in the urine, while the urine turns red;
• colic, which can be constant or manifest in sharp attacks (you can understand colic by the cat's anxiety, throwing around the room and meowing).

I would also like to draw attention to the fact that in case of blockage urinary tract urinary stones, the disease may be accompanied by stagnation of urine. Sometimes an animal can die from uremia (poisoning of the body by products of stagnant urine). The number of stones can vary from one to several hundred. Stones injure the mucous membrane, as a result of which inflammation develops, which can cause diseases of the bladder, kidneys, and purulent urethritis. In the event that the disease process is complicated by pyelitis or pyelonephritis, that is, inflammation of the kidneys, then signs characteristic of these diseases may appear:

• temperature increase;
• weakness, oppression, which can be replaced by anxiety;
• the appearance of pus in the urine, while it becomes cloudy and has an unpleasant odor.

If at least one of the signs listed above has been noticed in a cat, then it is advisable to contact a veterinary specialist. It is not possible to make a diagnosis on your own at home. In the veterinary clinic, it is necessary to accurately describe the signs that were observed, as well as to talk in detail about feeding. You will also need to take a urine test of the cat to the laboratory. In some cases, they may suggest ultrasonography or x-ray.

In the laboratory, the presence in the urine of crystals of uric acid salts, the epithelium of the renal pelvis, and urinary cylinders is usually determined. Based on laboratory data, the results of ultrasound (X-ray) and make the final diagnosis of urolithiasis in a cat. However, urinary tract disease does not always indicate the presence of stones, they can have different causes and differ for dogs and cats.
Diseases of the lower urinary tract, in essence, can be explained by the following factors:

1. Cystitis (inflammation of the bladder) of infectious origin: when it is found in the urine a large number of bacteria. In cats, infectious cystitis is quite rare.
2. Idiopathic cystitis: common in cats, among which it accounts for more than 60 percent of urinary tract diseases. Many factors are involved in the development of this disease, such as stress, living conditions (presence of several cats in the house, keeping exclusively indoors, etc.). Surprisingly, nutrition plays a key role in the prevention and treatment of this disease.
3. Urinary stones (stones), which in animals usually form in the bladder, and not at all in the kidneys, as in humans. The main role in the prevention of recurrence of this disease is played by the diet.
4. Tumors.

To make an accurate diagnosis, it is necessary to pass a clinical urinalysis and only after its results, draw appropriate conclusions.

What is a urinary stone

Actually urinary stones are formed from the crystals present in the bladder. These same crystals, even if they do not form stones, can nevertheless cause clinical signs of urinary tract disease or even obstruct the flow of urine, which is life-threatening for the animal.

Crystals are formed when the urine is saturated with minerals as a result of metabolic or feeding disorders, which can create favorable conditions for the formation of urinary calculi. Most people are under the delusion that dry food promotes the formation of urinary stones. After all, with the right selection of high-quality food, it helps to protect the urinary tract.

Types of stones

Struvite stones: the most common are formed from phosphate, ammonium and magnesium ions. Often formed in dogs with any urinary tract infections, which complicates the course of the disease. In this case, both problems must be treated at the same time.

Calcium oxalate stones: are also common in both dogs and cats.

Ammonium urate stones: are much less common, often associated with liver disease.

Cystine stones: the most rare of all listed.

Stones can be of various sizes, single or multiple, one or more types at the same time. To prescribe the correct treatment, it is very important to determine the type of stones. Therefore, if your pet has a stone removed surgically, take it for analysis, according to the results of which the veterinarian will be able to choose the appropriate treatment for the animal. Treatment will likely include antibiotics to fight a possible bladder infection, anti-inflammatory drugs to reduce inflammation in the urinary tract, or drugs to change the pH of the urine. With idiopathic cystitis, pheromones can go in to help the animal cope with stress.

Struvite stones can be dissolved by following special diets. Usually such a diet contains a higher percentage of sodium, but its amount is safe for the health of the animal, which stimulates thirst and fluid intake, and therefore leads to the formation of less concentrated urine. In addition, the composition of such food reduces the concentration of minerals in the urine and acidifies it. Cystine and ammonium urate stones can also be dissolved, but this requires a completely different diet that alkalizes the urine. Calcium oxalate stones are insoluble. So, they will have to be removed surgically under anesthesia.

Urinary stones in cats can be up to one centimeter in diameter. They are not formed under the influence of food, but food can reveal their presence.

predisposition to disease

Breeds most commonly affected by oxalate formation include:

• Burmese;
• Persian;
• Russian blue;
• Maine Coon;
• Siamese.

The concentration of urea in the animal's urine directly depends on the content of proteins (protein) in the animal's diet. Excessive protein content in cat food (beef - 16.7%, chicken - 19%, fish - 18.5%, cottage cheese - 16.7%), with impaired purine metabolism (the end product of purine metabolism is uric acid), leads to development of uric acid urolithiasis in cats. Reducing the protein content has a positive effect, as it helps to reduce the amount of substrate favorable for the growth of pathogenic bacteria. Lactic acid diet and vegetarian diet contribute to the development of alkaline urolithiasis

The risk of developing urolithiasis in cats is higher:

• with constant home maintenance;
• after castration, sterilization;
• with excess body weight;
• with improper feeding;
• in cats (cats suffer from urolithiasis much more often than cats);
• in adult animals (struvite stones are more often formed in cats under 4 years old, the peak of oxalate stones formation occurs in the period of 10-15 years).

Prevention and treatment

Prevention comes down to improving the conditions for feeding and watering the cat. Be sure to take care of a varied diet. Try to avoid giving monotonous feed and drinking hard water. Introduce vitamins into your pet's diet. Don't forget to take regular walks. You can also sometimes take urine for analysis to the laboratory, where it will be possible to examine the sediment to detect the disease in the early stages.

For the treatment of urolithiasis in cats, symptomatic treatment is used, it is advisable to use painkillers, as well as antispasmodics.

In rare cases, probing the urethra or even surgical removal of urinary stones may be necessary.

The following treatment regimen is usually used:

• antibiotic therapy is recommended to relieve inflammation;
• It may not be superfluous to give the cat medicinal herbs: a decoction of bearberry leaves, parsley root;
• the use of drugs that disinfect the urinary system (furadonin, urosulfan, metronidazole);
• for destruction, removal of stones, sand - uradon, cystone are prescribed inside;
• removal of spasm, elimination of pain, colic - for this, no-shpu, analgin, baralgin or any other antispasmodic drugs are administered intramuscularly;
• displacement of the stone - usually a solution of novocaine is injected into the urethra and after a while they try to move the stone into the bladder (this manipulation is carried out if the cat has a blockage of the urethra with urinary stones);
• washing the bladder with anti-inflammatory drugs (sodium chloride solution with an antibiotic).

diet therapy

struvite stones, can be dissolved with special diets from Royal Canin. and Hills. This diet contains more sodium (in a safe amount for the cat), which stimulates thirst and therefore water intake, resulting in more dilute urine. Also, this food reduces the concentration of minerals (magnesium and phosphorus) in the urine and acidifies it.

With struvite stones, it is necessary to exclude:

• foods high in calcium compounds;
• milk;
• cottage cheese;
• egg (yolk);
• curdled milk.

• boiled beef;
• veal;
• egg (protein);
• carrot;
• oatmeal (in a small amount);
• liver, cabbage, fish (eel, pike).

In the application of dietary rations, it is necessary to take into account some nuances. The acidifying effect of feed on urine can be both excessive and insufficient. Therefore, in the process of treatment, repeated urinalysis is required. All medicinal feeds have contraindications, therefore, before giving them to your pets, you should contact your veterinarian. Cat food manufacturers do not recommend combining ready-made dry or canned food with natural (homemade) food. It is strictly forbidden to mix ready-made food with porridge or other products in a cat feeding bowl. Fresh, clean water (preferably filtered) should be available to the cat at all times.

Uric acid and cystine stones can also be dissolved. To dissolve them, a special diet from Royal Canin or Hills is used, which alkalizes the urine.

Unfortunately, calcium oxalate stones, are insoluble. Therefore, they will have to be removed surgically under general anesthesia.

At oxalate stones the diet should limit the intake of:

• oxalic acid;
• liver;
• kidneys;
• foods rich in calcium (milk, cheese, cottage cheese, etc.).

It is necessary that the following foods be present in the diet:

• beet;
• cauliflower;
• peas, legumes;
• boiled meat;
• fish;
• cereals;
• vegetables.

In extreme cases, a cystomy is performed. This is a surgical opening of the bladder cavity to remove stones. Such measures are taken if the stones reach sizes that do not allow extraction using less radical methods.

During the treatment of urolithiasis, it is also necessary to correct and maintain the normal functioning of all body systems, namely: to intensively fight intoxication and replenish the loss of blood and fluid, control the function of the kidneys and heart, and prevent hypothermia of the animal. This whole complex of tasks is solved by competent infusion therapy (droppers) in combination with additional studies of urine, blood and cardiac function.

The detection of tripelphosphates in the urine of a cat means that the animal develops urolithiasis, which requires immediate contact with the veterinarian. If during the period of exacerbation of symptoms, the pet is not provided with assistance, for example, surgical, then it may die. Regardless of whether the cat drinks or not, urine constantly enters the bladder and stretches it to a critical size. Blood vessels rupture on the inner walls, a lot of blood enters the lumen, and urine enters the blood vessels, intoxication of the body develops, which is accompanied by convulsions, body tremors, and vomiting.

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Treatment of disease in cats

Treatment of urolithiasis is carried out in several ways:

• drug therapy, homeopathy;
• the use of herbal medicine includes herbal preparations to reduce inflammation and dissolve uralitis;
• operation epicystomy, urethrotomy or catheterization of the bladder;
• dietary method, including the stage of dissolving stones, preventing the appearance of new ones, reducing harmful substances in the diet, increasing the volume of urine formation, maintaining the required pH;
• magnetic therapy of a pulsed nature.

They try to eliminate pain with the help of medicines, increase the dissolution of salts, make the texture of stones more loose, and prevent relapses:

• antispasmodics are used to eliminate pain, these include Spazgan, Baralgin;
• the infection is fought with sulfanilamide drugs (Sulf-120, Urosolfan), antibiotics (Albipen LA, Cefa-kure, Enprofloxacin), anti-inflammatory drugs (Dexafolt), the drug Cat Ervin is effective, the latter is injected into the bladder after urine is removed;
• relieve spasms of smooth muscles with drugs Catosal or Gamavit;
• they clean the lumen of the canal and break the plugs in the urethra with the help of a catheter and treatment with Cat Ervin, a bath heated to 40 ° C on the lower part of the animal's body;
• quickly improve the condition of the pet by introducing Gamavit under the skin with the simultaneous administration of Fosprenil and Maksidin;
• the use of Avisan and Cyston is allowed, but the dosage in the instructions is indicated for a person, therefore for cats it is recalculated by weight, pay attention to the allergic manifestations of the cat to the incoming plant components.

For cats, medicines containing essential oils and glycerin, this will lead to the death of the animal (Cistenal, Urolesan, Fitolizin, Pinobin).

If drug treatment was carried out, then in 50-60% of cases there are repeated relapses.



homeopathic remedies

Long-term therapy with homeopathic remedies controls the condition of the inner mucous layer of the bladder. Medicines are prescribed Mucosa, Berberis-homaccord, Compositum. According to the instructions, the medicines are given several times a week, dissolving in water for drinking. In the acute phase, during therapy with homeopathic preparations, Traumeel is prescribed, it is injected under the skin several times a day or after surgical intervention drip applied after 17-30 minutes.

If the formation of tripelphosphates is a consequence of chronic pyelonephritis, then Compositum-cantharis and Berberis-homaccord are used as the main therapy.





Bladder catheterization and surgery

Catheterization is ordered by a veterinarian if palpation reveals a hard, overflowing bladder, sometimes with partial patency. The procedure is done under general anesthesia, the doctor gives a relaxant based on the anatomy of the animal and its character. The catheter is placed after the onset of anesthesia, it is carefully inserted and the formation of stones and crystals is destroyed, the accumulated urine is removed through the cavity of the instrument and the internal cavity of the bladder is treated with drugs that stop inflammation.

Take a small amount of urine at the same time laboratory research. If necessary, the catheter is fixed for several days (sutured). Drug therapy is immediately determined, and after receiving the results of tests that recognize the type of struvite, diet therapy is prescribed using medicated feed.

If only one kidney is affected by uralitis, then it is removed along with tripelphosphate growths. Surgical removal is indicated in the case of accumulation of urolithic crystals in the ureters, this is a mild form, and removal is not difficult. After the operation, complications arise in the form of developing renal failure, so attention is paid to the implementation of recommendations for prevention.

Effective results and positive prognosis are given after the extraction of tripelphosphates from the insides of the bladder during cystotomy. The operation consists in opening the organ and removing urolithic crystals.



The cat is sick: does not eat or drink, constant vomiting - possible causes

Method of impulse magnetic influence

The radiation source is applied to the area above bladder and spend several sessions (up to 10), each of which consists of 50 pulses with a power of 500 mT. Low-frequency electromagnetic radiation has an antispasmodic, sedative and analgesic effect, changes the chemical and physical properties of urine, increasing its ability to dissolve substances.



This method is considered effective, painless and well tolerated by cats, the procedure does not cause concern, while the mortality rate is reduced to zero compared to other methods. After pulsed MT, the passage of urine improves during the first three days for animals in serious condition, and the complete removal of characteristic symptoms is observed after a week.

The magnetic pulse effect helps in cases where the urethra is filled with tripelphosphates throughout its entire length and it is not possible to insert a catheter. The preliminary procedure not only facilitates the placement of the catheter, but in some cases allows you to dispense with the introduction. After treatment with low-frequency electromagnetic current, relapses are observed in 14% of diseases, while traditional therapy allows the recurrence of symptoms in 40% of cases.

Phytotherapy

Allows you to use the properties of plants to dissolve and remove urolithic formations. At the initial stage of the disease, Cat Erwin and Phytoelite Healthy Kidneys are prescribed.

Herbs are used to make infusions of woolly herva (half-pale), highlander bird, parsley root, watercress, and decoctions of bear ears (bearberry) are prepared, which can dissolve stones.



Preventive diet

The analysis of feeding methods showed that the choice of products is important in preventing the onset of the formation of tripel phosphates:

• the incidence in cats and cats receiving natural fish and meat is 17% of the total number of cases;
• only fish dishes contribute to the development of the disease in 24%;
• the combination of natural food with artificial food gives the highest percentage of struvite (38%).

Recent studies have confirmed that adherence to natural products increases the risk of crystal formation, and branded dry food reduces it. The combination of natural and artificial products is unfavorable, since the amount of vitamins, minerals and nutrients is difficult to trace. It is important for a pet to get the required minerals, and in old age, cats and cats have a metabolic disorder, which affects the full absorption. In this case, feed with vitamin supplements are indispensable.

Acidification of urine is promoted by an increase in proteins in the diet due to a violation of protein metabolism and an increase in the content of uric acid. Eating only fish and meat reduces the production of vitamin B1 and leads to an acidic environment in the ureters, this includes a lack of vitamin A. An increase in alkaline indicators and the formation of struvites is affected by the enrichment of the diet with fish and hercules (phosphorus and magnesium).

The formation of uroliths is noted in the urinary canals of animals that are overweight. This unnecessarily burdens the urinary system, which is not adapted to the disposal of decay products, which predetermines the onset of crystallization. Big weight the cat does not allow him to actively move, which reduces metabolism.

High-quality dry food is used for feeding; when choosing, attention is paid to the content of magnesium, phosphorus and proteins per 100 g of product. Branded dry granules are recommended at a rate of 37–50 g per day, and low-quality ones give 120 g each. If the content of microelements per 100 g is the same, then when eating a cheap option, the cat receives more substances than necessary.

Fluid intake has been studied in relation to various diets, as changes in water volume affect the amount of urine and mineral content. Pay attention not only to the excretion of urine, but also moisture with feces, other fluid export from the body. Water balance also depends on fat content and energy.



A high-fat diet (about 30%) increases urine output, and a low-calorie, fat-free diet increases the concentration of fluid in the stool. Regardless of the type of food, cats and cats drink 120-240 ml of water per day. The increase in the volume of water consumed is influenced by climate, season, nutritional components, stress and other factors. Appointment proper nutrition is:

• preventing the growth of struvite crystals and uroliths in cats and cats;
• exclusion of formations of tripelphosphates in animals with a tendency to obesity;
• dissolution of struvite;
• prevention of relapses and further growths;
• moderate reduction in vitamin D intake.

There are specially designed diets for each type of stones individually, as food recommendations are different. To prevent struvites from developing, cats are given meat and other protein foods, as they acidify urine and do not allow an increase in alkaline reaction. Do not eat cereals, as they alkalize the body. For more urine formation, sufficient drinking is organized for the animal. The development of urolithiasis in cats and cats is an urgent problem when keeping pets, both animals and owners suffer from this. The main thing in this matter is the timely detection of the disease and contacting the veterinarian when the disease is at an early stage.

In urolithiasis, the formation different types uroliths. Let's stop at one of them. Struvite in cats - what is it, how do they form, what methods of treatment are effective? We will talk about this in our new article.

If you see that your cat is having difficulty urinating, that trying to urinate is accompanied by pain, and there is blood in the litter box, you need to take him to the veterinarian as soon as possible. It is possible that your pet has urolithiasis, or urolithiasis. In KSD, urinary stones form due to a metabolic disorder in the kidneys, urinary tract, and/or bladder of the cat. With a different acid-base balance of urine, various salts can precipitate. Which salts are deposited determines what type of stone is formed in the cat's bladder.

Struvites - it is a phosphate stone. They can be hard or loose, the color of struvites is cream or yellow. Under a microscope, they look like an elongated prism with recognizable diamond-shaped edges. In cats, this is the most common type of stone, accounting for up to 80% of cases. Struvite is soluble, which is essential for the treatment of this condition in cats. These stones are also radiopaque, making them easy to visualize on an x-ray and make a diagnosis.

Symptoms of struvite formation in a cat

Your cat's symptoms of struvite mimic those of kidney stones in general. The main symptom is difficult urination or its absence. The number of urination may be more or less than usual, the volume of one urination is usually reduced, and blood may appear in the urine. Read more about the symptoms of urolithiasis in our article "Urolithiasis in Cats".

Establishing diagnosis

If your cat has been diagnosed with urolithiasis, the next step in the diagnosis is to determine the type of stones and their location. Determining the type of urinary stone is extremely important for further treatment. The main type of diagnosis in this case is a urinalysis. The nature of the change in acid-base balance and sediment can tell a lot about what kind of stones have formed in the cat's urinary tract.

Another type of examination is X-ray. Since struvites are radiopaque, they will show up well on x-rays. An ultrasound examination is also used to clarify the diagnosis.

Struvite treatment in cats

Since struvite is soluble, the main treatment is diet. To dissolve this type of stone, the cat's diet must contain a limited amount of protein, calcium, phosphorus and magnesium, as well as maintain the pH of the urine at a certain level. It is quite difficult to prepare suitable food for a sick cat on your own, however, there are lines of therapeutic food for cats with urolithiasis on sale. Each type of stone has its own food, so before giving such food to a cat, be sure to consult a doctor. Prescribing the wrong food can exacerbate the problem.

Antibiotics are also commonly used to treat struvite stones in cats, as these stones are usually accompanied by a urinary tract infection.

More about treatment different types urolithiasis can be read on our website in the article "Urolithiasis in cats" mentioned above.

Prevention of struvite formation in cats

Prevention of struvite formation in particular and urolithiasis in general lies mainly in a balanced diet (it is better if it is a good ready-made food) and clean water. To monitor the condition of the cat every six months, you need to take a urine test.

Lower urinary tract disease is a common disease in dogs and cats, occurring in about 7% of cats and 3% of dogs seen in clinics. Urolithiasis is a specific type of lower urinary tract disease characterized by the presence of crystals (crystalluria) or large stones (uroliths) in the bladder or lower urinary tract in the urine, along with certain clinical signs. Urethral plugs often have a different mineral composition and are also classified as urolithiasis. In cats, urolithiasis is considered as one of the diseases included in the group of diseases of the lower urinary tract. This group of diseases is called feline lower urinary tract disease(FLUDT) (feline lower urinary tract disease).

Urolithiasis is associated with a number of different risk factors and is classified by etiology according to mineral composition. There is a breed predisposition to certain types of urolithiasis in dogs. Dogs are also more prone to infectious urolithiasis than cats. Establishing the mineral composition of uroliths is important, because prevention and treatment should be aimed at dissolving (removing) a certain type of uroliths. This chapter describes the types of uroliths found in dogs and cats, risk factors, and the use of diet to treat, control, and prevent recurrence of urolithiasis.

DEVELOPMENT OF THE DISEASE AND CLINICAL SIGNS

Urolithiasis develops in adult animals. In cats, this disease rarely occurs in individuals younger than one year old, with the first diagnosis of urolithiasis most often between the ages of 2 and 6 years. In dogs, urolithiasis is most often diagnosed at 6.5-7 years of age. In both cats and dogs, the type of uroliths depends on age. For example, struvite, urate, and cystine are more common in young dogs, while oxalates and silicates are more common in older dogs. Although both males and females are susceptible to urolithiasis, a sexual predisposition to a particular type of urolith has been noted. For example, cats have a higher prevalence of struvite urolithiasis than cats, but more than 70% of cases of calcium oxalate stones occur in cats. Recent studies in dogs have shown a similar relationship between animal sex and urolith type. Struvites, urates, and apatites are more common in females, while oxalates, cystines, and silicates are more common in males.

Breed predisposition to urolithiasis has been studied in both dogs and cats. Compared to domestic shorthair cats, Siamese cats are less likely to develop FLUTD, while Persians are more susceptible to these diseases. More recent studies on the predominance of calcium oxalate uroliths in cats have found that Himalayan and Persian cats are more prone to this type of urolithiasis. Researchers believe that such breed characteristics as low level activity and predisposition to obesity can influence the development of the disease. The breed predisposition to urolithiasis in dogs is more pronounced. Calcium oxalate uroliths are most common in miniature schnauzers, Lhasa Apso, and some terriers. Urate calculi are most commonly found in Dalmatians and English Bulldogs. Dachshunds, English Bulldogs, and Chihuahuas have an increased risk of developing cystine stones.

The clinical signs of urolithiasis in cats and dogs are nonspecific and depend on the location, size, and number of crystals or uroliths in the urinary tract. Uroliths can be located in the bladder, urethra, kidneys, or, very rarely, in the ureters. Although uroliths can be several millimeters in diameter, most are sand-sized or even microscopic. Early clinical signs are as follows: frequent urination, urinary incontinence, urination in the wrong places. There is also hematuria and a strong smell of ammonia from the urine. Pet owners also notice signs of dysuria such as frequent posture or straining during urination (often confused with constipation) and frequent licking of the urogenital area. These signs are often the only ones owners report to the doctor. In some cases, partial or complete obstruction of the urethra may develop. With obstruction, a different combination of mineral components and protein substances form a plug that repeats the shape of the lumen of the urethra. Although urethral obstruction can occur in any dog ​​or cat, it is most common in cats. This is due to the fact that cats have a long and narrow urethra and there may be a sudden narrowing of the bulbourethral glands at the junction of the urethra with the penis. If the obstruction is complete, uremia develops rapidly and is characterized by abdominal pain, depression, anorexia, dehydration, vomiting, and diarrhea. Increased urinary pressure can cause renal ischemia leading to damage to kidney tissue. In severe cases, an overfilled bladder can rupture, leading to rapid peritonitis and death. Uremia alone leads to coma and death within 2 to 4 days, so partial or complete blockage of the urinary tract requires urgent intervention (Table 32-1).

TYPES OF UROLITHES

According to the mineral composition, uroliths in cats and dogs are most often struvites (magnesium, ammonium, phosphate) or oxalates. Less common: ammonium urate, xanthine, cystine, calcium phosphate and silicate. Until recently, struvite was the most common urolith in cats, followed by calcium oxalate. However, over the past 10 years, the mineral composition of uroliths obtained from cats has changed towards an increase in oxalate uroliths. A similar situation has been found in dogs. The main difference in struvite urolithiasis in dogs and cats is that most struvite uroliths in cats do not cause urinary tract infections (these are called sterile struvites). In dogs, struvite urolithiasis is often accompanied by a urinary tract infection.

STRUVITE UROLITHIASIS IN CATS

Early studies showed that more than 95% of feline uroliths were of the struvite type. However, the occurrence of this type of uroliths has changed significantly over the past 10 years. A 1981 study at the Minnesota Urolith Center found that 78% of feline uroliths were struvite and only 1% were oxalates. By 1993, the incidence of struvite urolithiasis had decreased to 43%, while the incidence of calcium oxalate uroliths had increased to 43%. Although there was a significant increase in the incidence of oxalate urolithiasis during this period, the incidence of calcium oxalate crystals in urethral plugs remained the same at 1%.

Because struvite uroliths are the most common in cats, all research in the early 1980s was focused on preventing the formation of these crystals in the urine and developing diets for cats with struvite urolithiasis. Although a significant number of cases of urolithiasis have been found to be due to various causes, preventing the formation of struvite crystals is an important and effective part of controlling urolithiasis. The present studies have shown that three types of struvite uroliths are most common. These are: sterile struvite uroliths, uroliths on the background of infection and urethral plugs containing varying amounts of struvite crystals. Treatment and diet therapy is aimed at dissolving struvite crystals and stopping infectious and inflammatory processes, if any are present.

STRUVITE FORMATION

Several conditions are necessary for the formation of struvite crystals in the urinary canal. First, there must be a sufficient concentration of the constituents: magnesium, ammonium and phosphates. Also, these substances must be in the urinary canal for a time sufficient for crystallization. The excretion of concentrated urine and small portions of urine also contribute. Also, a certain pH level is required for the formation of crystals. Struvite is soluble at a pH value below 6.6, struvite crystals form at a pH value of 7.0 and above. The formation of sterile struvites in cats is associated with the factors described above, and is also characterized by the absence of urinary tract infections. However, while alkaline urine is required for primary struvite formation, studies in cats with sterile urolithiasis have shown that the urine of affected cats is not always alkaline. For example, in a group of 20 cats with naturally occurring sterile struvite urolithiasis, urine acidity at diagnosis was 6.9 ± 0.4. Therefore, it is important to remember that making the urine neutral or acidic may not be the primary treatment for struvite urolithiasis.

Urolithiasis resulting from infection is less common in cats than in dogs. Infection involving urease-producing bacteria (especially staphylococci) is accompanied by signs of urolithiasis and the presence of struvite in the urinary tract is essential for diagnosis. These bacteria produce the enzyme urease. Urease hydrolyzes urea to ammonia, causing an increase in the concentration of ammonium and phosphate ions, two components of struvite uroliths. An increase in the concentration of ammonium ions further leads to alkalization of urine. Cats may be predisposed to infective urolithiasis if the local barrier is compromised and the amount of urea in the urine is high. However, because many cats are inherently resistant to urinary tract infections, infective struvite urolithiasis is less common than sterile urolithiasis.

FEED RISK FACTORS

The most important risk factors for the development of struvite urolithiasis are:

Feed additives that alkalinize urine

High levels of magnesium

Low digestibility and calorie content

Feeding mode

Drinking animal

One of the risk factors that the owner can change and control during the treatment and prevention of urolithiasis is the cat's lifestyle. One of the conditions necessary for the formation of struvite in the urine is the presence in the urine in a certain concentration of three constituent elements: magnesium, ammonium and phosphates. Cat urine always contains a high concentration of ammonium because cats consume large amounts of protein. Phosphate concentrations in the urine of healthy cats are usually also sufficient for struvite formation, regardless of dietary phosphorus intake. The concentration of magnesium is usually quite low and directly depends on its content in the feed.

Early studies of struvite urolithiasis in cats focused on dietary magnesium as the most important cause of the disease. Changes in dietary magnesium levels to develop or prevent phosphate urolithiasis have been well studied in rats and sheep. These studies have been used to confirm the role of this mineral in the etiology of urolithiasis in domestic cats. Some of the earliest studies showed that urethral obstruction and bladder stone formation developed in adult cats fed a diet containing 0.75 and 1% magnesium and 1.6% phosphate. The uroliths that blocked the urinary canal consisted mainly of magnesium and phosphates. Subsequent work showed that a high level of phosphorus in the diet is not a necessary condition for the formation of uroliths. But phosphorus increases the risk of urolithiasis if magnesium levels in the diet are also high. However, if dietary magnesium is low, the risk of developing urolithiasis is reduced regardless of the level of phosphorus in the diet. In more recent studies, groups of cats were fed diets containing 0.75%, 0.38%, and 0.08% magnesium on a dry matter basis. 76% of cats fed 0.75% magnesium diets and 70% of cats fed 0.38% magnesium diets developed urolithiasis and urinary tract obstruction in less than 1 year. No cat with 0.08% magnesium in the diet was found to have urolithiasis. When randomly selected healthy cats were fed diets containing high levels of magnesium or high levels of magnesium and phosphorus, they developed urethral obstruction. Stones blocking the urethra were identified as struvite stones in one in seven cats.

These studies have shown a relationship between increased dietary magnesium levels and an increased incidence of uroliths and urethral obstruction in cats. However, the significance of these studies on the role of dietary magnesium in causing struvite urolithiasis in cats is debatable. Dietary magnesium content in these studies was significantly higher than is commonly found in commercial feeds. The need for a domestic cat in magnesium during the period of growth and later life is 0.016%. AAFCO believes that cat food should contain a minimum of 0.04% magnesium. Most commercial cat foods contain more magnesium, but still less than 0.1%. Although magnesium is found in many food ingredients, it is not 100% available, but there is enough available magnesium to meet the needs of cats. Magnesium levels in commercial cat food are higher than the minimum required for a cat, but still significantly lower than levels used in studies to promote struvite formation.

Another problem with the data obtained from these studies is the composition of the experimentally induced uroliths. Struvites, formed during the natural course of urolithiasis, are composed of magnesium, ammonium and phosphates. Struvites in experimentally induced urolithiasis consist of magnesium and phosphates, without the inclusion of ammonium. The composition of urethral plugs in the natural and experimental course of the disease also differs. Experimentally induced urethral plugs consisted mainly of struvite crystals. Urethral plugs extracted during the natural course of the disease mainly consisted of a protein substance, with inclusions different quantity minerals (in most cases struvite), urinary canal tissues, blood.

The most important point of contention in these studies is the form of magnesium supplements used in the experiment. Studies have been conducted on the effects of two different forms of magnesium supplementation on adult cat urine acidity. Studies have shown that the addition of 0.45% magnesium chloride to the basic diet leads to a significant decrease in urine acidity. When 0.45% magnesium oxide was added to the same diet, the reaction of the urine medium was much higher, more alkaline. In the ad libitum regimen, the urinary response of cats on the basal diet was 6.9; with the addition of magnesium chloride - 5.7; with the addition of magnesium oxide - 7.7. Microscopic examination of urine sediment from cats on a basal diet supplemented with magnesium oxide showed crystals, but no crystals were found in cats fed a diet supplemented with magnesium chloride. That is, at the same level of magnesium in the diet, the reaction of the urine and the formation of crystals depend on the form of magnesium in the supplement. The conclusion that high levels of magnesium cause struvite formation is debatable in light of research into the effects of different supplements—magnesium chloride and magnesium oxide—on urine acidity. Experimentally induced and naturally occurring urolithiasis are similar, but the above controversies show that magnesium in the diet is not the only one responsible for the natural development of struvite urolithiasis. That is, the level of magnesium in the feed is not as important a risk factor as the acidity of the urine, the volume of urine and the water intake of the animal.

As previously discussed, struvite crystals form in cat urine at pH 7.0 or higher and are soluble at pH 6.6 or lower. In a healthy cat, urine acidity is usually 6.0 - 6.5, except during the period after a meal. In all animals, after eating, the urine reaction increases within 4 hours after eating. This effect, the postprandial alkaline wave, is caused by a compensation by the kidneys in response to the release of gastric acids during digestion. To compensate for the loss of acids and maintain the normal acidity of body fluids, the kidneys secrete alkali ions, which leads to an increase in the reaction of the urine environment. The magnitude of the alkaline wave depends on the size of the portion eaten and the content of acidifying or alkalizing components in the food. The reaction of the urine environment in cats after eating can reach 8.0.

Several studies have shown the importance of urine acidity in the formation of struvite crystals in cat urine. One study showed effects on urinary acidity and struvite formation in adult cats fed canned food, dry food, or dry food supplemented with a urine acidifier (1.6% ammonium chloride). The highest urine acidity (7.55) was in cats fed dry food. The addition of ammonium chloride to the dry food reduced the acidity of the urine to 5.97. When feeding cats with canned food, the reaction of the urine medium was 5.82. Interesting results in this study were obtained in the study of struvite formation. Struvite crystals formed in the urine of 78% of dry-fed cats, but when ammonium chloride was added to dry food, only 9% formed crystals. The levels of magnesium and other minerals on a dry matter basis were similar in both types of dry food (regular and ammonium chloride supplemented). None of the cats developed struvite crystals in their urine when fed canned food. ???When urine samples of all cats were acidified to 7.0 with sodium hydroxide, 46% of cats fed canned food and all cats fed dry food supplemented with ammonium chloride had typical struvite formation.? ?? These studies have shown that at the same level of energy, dry matter and magnesium, the formation of struvite is affected by the acidity of the urine.

Regardless of dietary magnesium levels, dietary manipulation of urine acidity causes struvite formation. When feeding dry food containing high levels of magnesium (0.37%) to adult cats, the addition of 1.5% ammonium chloride resulted in a urine reaction of 6.0 or less. Cats fed a diet without ammonium chloride supplementation had a urine reaction of 7.3. Seven of 12 cats on a diet without ammonium chloride supplementation had struvite uroliths and urinary obstruction twice, but only two cats fed an acidifying diet had urinary obstruction once. When ammonium chloride was added to the diet of seven cats with urinary obstruction, no more cases of struvite formation or urinary tract obstruction were observed. Radiographic examination prior to ammonium chloride supplementation revealed clearly visible uroliths, which dissolved within 3 months of feeding an acidifying diet. Similar results were obtained when feeding diets containing magnesium in an amount close to that of industrial feeds. Cats fed a diet containing 0.045% magnesium, struvite formation and clinical signs of urolithiasis were found if the diet had an alkalizing effect. However, when ammonium chloride was added to the diet as an acidifying agent, the clinical signs of urolithiasis disappeared within 4 days and no longer appeared when fed an acidifying diet.

The domestic cat is a carnivorous mammal. Compared to the diet of omnivores and herbivores, the diet of carnivores causes an increase in acid excretion and a decrease in urine acidity. Acidification of urine is a consequence of high levels of sulfur-containing amino acids in meat. Oxidation of these amino acids leads to the excretion of sulfates into the urine and concomitant acidification of the urine. A diet containing a high percentage of meat contains less potassium salts than a cereal diet. Potassium salts have an alkalizing effect on urine. The inclusion of a large amount of cereals and a small amount of meat in commercial cat food can provoke the development of struvite urolithiasis. For example, the commercial feed used in the studies that caused struvite formation contained 46% cereal in the form of wheat flour. While some grains are necessary for proper passage of food through the GI tract and digestion, high grains can cause alkalinization of the urine. Adding a lot of meat to cat food leads to more acidic urine.

When selecting ingredients for the production of industrial dry cat food, attention should be paid to products that naturally acidify urine. Each ingredient should be investigated for its effects on urine reaction. For example, one study compared the acidifying effects on urine of corn gluten, chicken, and meat and bone meal. During testing, it turned out that corn gluten has the strongest acidifying effect. Unlike most plant proteins, corn gluten contains more sulfur-containing amino acids than chicken meat and meat and bone meal. Corn gluten is unusual in that it is a vegetable protein that acidifies the urine of predators.

WATER BALANCE AND URINE VOLUME

Decreased urine output is an important risk factor in the development of urolithiasis in cats. Diets that reduce the total volume of fluid circulating in the body lead to a decrease in urine output and an increase in its concentration. These two changes can cause struvite formation. It is believed that feeding dry food to cats leads to a decrease in the amount of fluid received and the volume of urine. Early studies have shown that cats fed dry food generally receive less water than cats fed canned food. When fed dry food, cats increased their fluid intake, but not enough to compensate for the low moisture content of the food. In another study, cats were fed the same complete diets with different moisture content. Cats fed a diet with a moisture content of 10% excreted 63 ml of urine per day. After increasing the feed moisture to 75%, the daily urine volume increased to 112 ml. Also, cats fed dry food had a higher specific gravity of urine. In both studies, differences in urine volume were thought to be due to reduced total water intake in cats fed dry food.

However, in contrast to the above studies, the other two groups of researchers did not find significant differences in water intake between cats fed dry food and canned food. Feed composition, especially fat content and calorie content, has been shown to affect fluid turnover in the cat's body. Studies have examined the effects of feed type, composition, and digestibility on urine output. A comparison of the three canned foods showed that cats fed 34% fat and 28% dry matter diets received significantly less dry matter than cats fed canned 14% fat foods. Faecal dry matter and moisture contents were lower in cats fed a high-fat diet. Because total fluid intake was the same for all cats, animals fed a high-fat diet excreted significantly more water in their urine to maintain hydration. Subsequent studies confirmed the importance of calories and fat levels by comparing a low-fat canned food to three dry foods. The amount of moisture in urine and faeces was about the same in all cats. In addition to the large difference in moisture content, the nutrient content of the low fat canned food was similar to that of the dry food. Energy availability in canned food and similar dry food was also almost the same (79.3% and 78.7% respectively) and was significantly lower than in high fat food (90.3%). Statistical analysis of these studies showed that the amount of water excreted in the urine of cats can be correlated with the level of fat and energy in the feed, a factor of 0.96 and 0.94, respectively. More fat means more urine.

Some investigators have suggested feeding only canned food to cats with a history of urolithiasis to increase total water intake and thereby increase urine volume and decrease urine specific gravity. However, the moisture content of the feed is still not as important as the calorie content, fat content and digestibility. Previous studies have shown that low-digestible canned food does not cause an increase in urine volume if a large amount of fluid is excreted in the faeces. Conversely, the consumption of high-calorie and easily digestible dry or canned food reduces the total dry matter intake. This decrease is accompanied by a decrease in fecal volume and moisture content, as well as an increase in urine volume. This dietary influence may be important in the prevention of urolithiasis in cats, as the urine will contain lower concentrations of minerals than needed to form struvite stones. Also, an increase in urine volume increases the frequency of urination, and urine does not stay in the bladder long enough for struvite formation. High-calorie and easily digestible food - large volume of urine.

FEEDING MODE

The postprandial alkaline wave is a consequence of food intake and subsequent excretion and loss of acid in the stomach. The duration and magnitude of this wave is influenced by many factors. Domestic cats prefer to eat small meals every few hours during the day. This mode of feeding reduces the magnitude of the alkaline wave, but increases its duration. Conversely, depending on the alkalinizing effect of the food, food intake may cause large fluctuations or a shorter duration of the postprandial alkaline wave. The effect of feeding regimen varies with the type of food, the cat's eating habits, and the various food ingredients.

In one study, cats were fed commercial dry food either freely available or once a day. The urine response of free-fed cats ranged from 6.5 to 6.9 during the day. In cats fed the same food once daily, urine pH increased to 7.7 within 2 hours of eating and then gradually decreased throughout the day. Another group of researchers fed cats two types of dry food and three types of canned food in the public domain, and the urine reaction was measured during the day. One of the dry foods and two of the canned foods produced urine with a constant response of less than 6.3. However, other dry and canned foods caused urine reactions ranging from 6.5 to 7.0 and higher. When the same foods were fed once a day, all of them, except for one dry and one canned, caused a sharp increase in urine acidity of more than 7.0 within 4 hours after the start of the meal. This level fell to 6.5 or less over the next 16 hours. One dry and one canned food produced a urine reaction of 6.6 or less, even after eating. This difference arose due to the difference in composition and different acidifying additives. More recent studies have examined the duration of the effects of acidifying diets. It has been found that free access to food is the most important condition for maintaining a urine reaction of 6.5 and below, even if the food contains acidifying components. The low urine reaction of cats with free access to food was explained by the fact that when a small amount of food is consumed many times a day, a small amount of gastric juice is released for each serving of food and a subsequent decrease in the postprandial alkaline wave.

In addition to the effect on the acidity of urine, the influence of the feeding regimen on the volume and composition of urine is important. A study was made of the relationship between feeding regimen, the amount of food and water consumed, and the volume and composition of urine. The maximum excretion of magnesium and phosphorus in the urine falls on the period before meals and does not coincide in time with the alkaline wave during the day. Free access to food has also been found to increase urinary frequency and total urine volume in cats compared to cats fed on a different diet. This influence of the feeding regimen is important for the prevention of urolithiasis. Studies have shown that the maximum concentration of the constituent substances of uroliths does not occur during the period of time when sedimentation is most likely. This is still not such an important factor for the formation of struvite. Studies have shown that the reaction of urine is directly dependent on the size of the serving of food, this relationship can be described as a linear function. In other words, as the portion size increases, the postprandial reaction of the urine environment increases. These studies also showed that as the postprandial urinary pH increased, the number of struvite crystals increased accordingly. Struvites do not form when the reaction of the urine environment is 6.6 or less.