“Struvite stones” and “calcium oxalate stones” are common kidney stones in dogs, which can lead to urinary tract obstruction and can lead to death if left untreated. In urgent cases, it is removed by laparotomy. This time, PetsVary explains the causes of kidney stones, how to deal with them, and dietary management to prevent recurrence.
What are Kidney Stones in Dogs?
Kidney stones (renal pelvic stones) is a disease in which a stone-like mass forms in the kidney (renal pelvis). Stones in the bladder are called “bladder stones”, stones in the ureters are called “ureteral stones”, and stones in the urethra are called “urethral stones”.
Dogs with kidney stones often have cystitis due to bacterial infection and are sometimes treated with antibiotics. Controlling cystitis is important to prevent recurrence.
Common breeds include Dachshunds, Shih Tzus, Bichon Frize, Chihuahuas, Miniature Schnauzers, Yorkshire Terriers, Labrador Retrievers, Dalmatians, Cavaliers, but can occur in any breed.
Types of Kidney Stones
Kidney stones are classified into the following types depending on the minerals that crystallize.
- Struvite stone
- calcium oxalate stones
- calcium phosphate stone
- cystine stones
- ammonium urate stone
- silica stone
Most of these stones in dogs are “struvite stones” or “calcium oxalate stones”, and in some cases, multiple stones are mixed. Struvite stones are more common in females and calcium oxalate stones are more common in males.
Symptoms of kidney stones in dogs
Kidney stones alone are usually asymptomatic and are often discovered incidentally during examinations. Bacterial infections such as cystitis and urolithiasis may cause the following symptoms. In addition, hematuria may occur due to long-term stones that damage the inner wall of the kidney (renal pelvis). If you have urolithiasis, you may experience symptoms such as:
- Glittery, smelly, or cloudy urine
- Dysuria/failure to urinate
- Frequent urination
- lick the pubic area
- feeling unwell/loss of appetite
- stomach ache
If the symptoms worsen, renal disorders such as pyelonephritis, acute renal failure, hydroureter, hydronephrosis, and ureteritis may occur. If a stone flows from the kidney, travels from the bladder to the urethra, and obstructs the urethra, it can lead to death due to bladder rupture or uremia.
what causes kidney stones in dogs
Since the cause of kidney stones is not clear, there are various theories, but basically it is believed that when the minerals contained in the urine become highly concentrated, they crystallize and gradually grow into a lump. Stones may form in weeks or months, and their rate of growth is affected by changes in pH caused by diet and bacterial infections.
Struvite stones (magnesium ammonium phosphate)
Normally, dog urine is slightly acidic, but if the urine becomes too concentrated or too alkaline, struvite crystals are likely to form, leading to calculi. Most struvite stones are caused by bacterial infection and are often accompanied by cystitis.
Urease, an enzyme produced by urease-producing bacteria, is responsible for making urine alkaline. Urease breaks down urea in urine to produce excess ammonia, which makes urine alkaline. Ammonia can also lead to inflammation of the bladder.
calcium oxalate stones
Calcium oxalate stones are caused by diet, and unlike struvite stones, they are more likely to occur when the pH of the urine is less than 6.5. In addition, when the intestinal oxalate-degrading bacterium Oxalobacter formigenes is reduced due to overdose of antibiotics, calcium oxalate crystals are likely to form.
Read Also: dog’s BCS (Body Condition Score)
Treating Kidney Stones in Dogs
Many kidney stones can be seen by ultrasonography (renal echo). Some stones, such as ammonium urate stones and cystine stones, do not respond to X-rays, so tests may be performed in conjunction with contrast imaging or CT. There are three treatment strategies:
- Removal by open surgery
- Dietary Dissolution
If a stone is found by chance during the test, or if there are no symptoms and only hematuria, follow-up is recommended. Regular examinations are necessary to check for stones flowing into the ureter, such as hydronephrosis. If you have hematuria, you should have regular check-ups with angiography to check for ureteral stones.
2. Dietary dissolution
Calcium oxalate stones cannot be dissolved by diet. It is said that small struvite stones can be dissolved with therapeutic food, but in my experience, they have not dissolved.
There is a possibility that it can be cured without surgery by diet therapy, but it takes time to dissolve, and there is a possibility that health conditions will be impaired due to the biased diet of therapeutic diets, and blood in the urine and dysuria will continue, and infection may occur. There is a risk of dysentery and urethral obstruction. It is important to take care at the crystallization stage as much as possible.
In order to prevent crystallization, therapeutic diets are formulated for the purpose of “making urine slightly acidic (less than pH 6.5) ” and “restricting protein, phosphorus, and magnesium, which are components of stones”. Do not give any other treats. Dogs often don’t like the taste and won’t eat, and if they don’t, consider other treatments.
3. Removal by laparotomy
Although open surgery has the risk of general anesthesia and requires hospitalization, the advantage is that it can be removed quickly. The cost of surgery varies depending on the location, size, and number of stones, and also varies from hospital to hospital. There is a burden on the body, so if there are other illnesses or senior dogs (old dogs), we will consider another method.
Prevention and Recurrence Prevention of Kidney Stones in Dogs
Treatment and preventive methods for kidney stones change depending on the minerals that crystallize. In the case of dogs, struvite or calcium oxalate are the most common, but either one will change the content of the diet to prevent recurrence.
Watch out for urinary tract infections in dogs with struvite stones. If you have symptoms such as blood in the urine or difficulty urinating, do not wait and see a doctor. Recurrence-prevention therapy should be continued throughout life. Protein, phosphorus and magnesium are restricted to make the urine slightly acidic (less than pH 6.5). Because it becomes high fat, you need to be careful of pancreatitis.
calcium oxalate stones
Dogs with calcium oxalate stones have a high chance of recurrence even if they pay attention to their diet and lifestyle. To reduce oxalic acid excretion in urine, do not give foods high in oxalic acid such as spinach, sweet potato, lettuce, broccoli, eggplant, and nuts.
Calcium does not need to be restricted as it binds with oxalic acid in the intestine and is excreted in the faeces. Conversely, limiting calcium intake increases oxalic acid excretion in the urine, which can lead to calculi. Shih Tzu, Miniature Schnauzer and Bichon Frize have been found to have high urinary calcium levels.
Preventive effect of therapeutic diet
Diluting the urine is an effective preventive measure for both struvite and calcium oxalate, so wet food is recommended over dry food. Calcium oxalate stones cannot be dissolved by therapeutic diets, but therapeutic diets are effective in increasing water intake, so a certain degree of preventive effect can be expected. You may also need to limit your protein intake, so talk to your doctor.
Summary (Kidney Stones in Dogs)
- Dogs are high in struvite or calcium oxalate
- May lead to death if it progresses to urinary tract obstruction
- The cause is unknown, but bacterial infection is a contributing factor
- Dietary therapy is effective depending on the type of stone
Kidney stones in dogs are mostly struvite stones and calcium oxalate stones, and they may be accompanied by high-risk diseases such as urinary tract obstruction and renal failure, so immediate treatment is required. A therapeutic diet is recommended for prevention, but recurrence is often seen with calcium oxalate. Don’t miss regular health checkups.