diet for dogs with kidney stones

Kidney Stones in Dogs

Nephrolithiasis in Dogs

Nephrolithiasis is the medical term for the condition in which clusters of crystals or stones -- known as nephroliths or, more commonly, kidney stones -- develop in the kidneys or urinary tract. The kidney is composed of thousands of nephrons, each consisting of blood capillaries and a series of tubes through which filtered fluid flows as urine is produced. The tubes of the nephron drain into ducts through which urine flows; these ducts eventually enter the renal pelvis and a tube through which urine follows into the ureter. Kidney stones or kidney stone fragments can also pass through this system of tubes and into the ureter, causing serious complications.

Both dogs and cats are susceptible to kidney stones. However, some breeds of dog are more susceptible to certain types of kidney stones than others. For example, kidney stones containing calcium and oxalic acid (known as calcium oxalate nephroliths) are more likely to be found in Lhasa Apsos, Yorkshire Terriers, and Miniature Poodles. Kidney stones containing uric acid (known as urate nephroliths), on the other hand, typically affect Dalmatians, Yorkshire Terriers, and English Bulldogs.

Symptoms and Types

Many dogs with kidney stones have no apparent signs; that is, the nephroliths are often not detected until diagnostic testing is done for other medical problems. Some symptoms that may occur include blood in urine (hematuria), vomiting, recurrent urinary tract infections, painful difficult urination (dysuria), and frequent urination with small volume of production (polyuria). Other symptoms may appear but vary depending on the location and type of the stones.

Note that some nephroliths may be inactive; meaning, they are not infected, not progressively enlarging, and not causing obstruction or clinical signs. Inactive kidney stones may not require removal, but should be monitored periodically (via urine analysis for example) for any changes.

Causes

There are a number of causes and risk factors that may contribute to the development of nephrolithiasis and the development of uroliths, such as the oversaturation of stone-forming material's in the dog's urine. Other potential causes include increased levels of calcium in the urine and blood, diets that produce high (alkaline) urine pH, and recurrent urinary tract infections.

Diagnosis

You will need to give your veterinarian a thorough history of the dogs health, including the onset and nature of the symptoms. He or she will then perform a complete physical examination, ultrasound imaging, and urinalysis. However, in order to confirm the diagnosis, identify the mineral content of the stones, and develop a proper course of treatment, pieces of nephroliths must be retrieved for analysis. This is usually achieved by performing a procedure known as extracorporeal shock wave lithotripsy (ESWL), in which stones are broken up within the urinary tract using sound waves.

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Treatment

Many dogs diagnosed with inactive kidney stones can be treated at home with proper medication administered in order to dissolve the stones. An adjustment to the dog's diet is also necessary. These dietary changes will be dependent on the chemical makeup of the kidney stone.

In severe cases, the dog may require immediate removal of the kidney stone(s) and hospitalization. There are a number of options for kidney stone removal, including surgery or ESWL.

Living and Management

Because kidney stones tend to recur, routine monitoring is essential. Most veterinarians recommend abdominal X-rays and/or ultrasound examinations every three to six months post initial treatment. A periodic urine analysis is also frequently recommended.

Prevention

If your dog is predisposed to nephrolithiasis, special foods and dietary management can be effective at preventing stone formation.

Kidney Stones in Dogs: What You Need to Know

Kidney stones form in dogs for a few different reasons. The different causes ultimately predict which type of nephro (kidney) + lith (stone) is most likely to form. And the type of stone affects what treatments might help. Dogs with small kidney stones really may show no signs at all. Kidney stones may show up on x-rays of the belly that are being taken for unrelated reasons, as a so called incidental finding. For instance, they may be discovered when you think your pooch may have eaten something he shouldnt have, like one of your favorite earrings. (Your vet found a stone, all right, but not the missing diamond you were seeking.) Since kidney stones dont seem to cause dogs as much pain as they do for people, why worry about them at all?

Why are kidney stones in dogs important?A kidney stone that allows normal urine flow out may be one that your vet watches closely, but ultimately leaves untreated. However, if the stone gets very large, or if little pieces break off and lodge in the ureter (the long narrow tube that connects each kidney to the urinary bladder) it becomes a ureterolith, and is likely very painful. Kidney colic, signaled by abdominal pain, discomfort and even vomiting, may result; the kidney may also swell and become damaged. If this should happen simultaneously to each kidney, and the blockage persists, your dog will likely become critically ill from the disrupted flow of urine. For these reasons, if you think your pets abdomen is painful, or his urinations change in any way, please contact your vet right away. A urinary obstruction is a life threatening emergency that must be treated!

Signs of kidney stones in dogsThe signs and symptoms of kidney stones could include:

Causes and types of kidney stonesMetabolic kidney stones, those stones formed due to some blood or urinary imbalance, are a bit more common in dogs than are stones caused by infection¹. Female dogs outnumber males when it comes to stones², and there are certain dogs and certain dog breeds that seem to be stone formers. They may form stones multiple times, despite ordinary precautions being taken to prevent them. Calcium oxalate is one of the most common types of kidney stones, and is common in the bladder, too.

Stones that form in the bladder or kidney because of chronic bacterial infection are usually struvite. The stone components are magnesium, ammonium and phosphate.

Some dog breeds with an increased risk of kidney stones are listed here²:

Diagnosis of kidney stonesStruvite and oxalate stones usually show up readily on plain radiographs, but small stones may be hidden by whatever else is in your dogs belly. Certain stones dont consistently image well either, especially urate stones, which are common in Dalmatian dogs, so simple x-rays may not give enough information. Once its found, predicting the stone type is challenging, so your vet will need some diagnostic aids to help with that. She will want to do some tests to see what impact the stone(s) may be having on your dogs kidney health, and whether other conditions may be present that might increase the risk of stones. If a kidney stone is suspected, or already diagnosed, your vet will likely want to have a minimum data base to start from, consisting of these tests:

• Complete blood count (CBC) Low red blood cells (anemia) or high white blood cells are important findings
• Blood chemistry with electrolytes Testing for evidence of kidney disease and risk factors for stone formation
• Urinalysis The urine quality may predict kidney disease and help identify white blood cells and red blood cells that suggest bacterial infection, or crystals that may help predict stone type
• Urine culture with susceptibility Identifies bacterial infection and best antibiotic choice(s)
• Abdominal radiographs (x-rays) to examine the size and shape of the kidneys and look for urinary stones
• Systemic blood pressure To identify an important complication of kidney disease

Additional tests that may be suggested:

• Abdominal ultrasound This will help verify the location of any stones and the suspected degree of any obstruction
• Contrast radiography Dye studies may be needed to confirm blockage and help to show the contribution that each kidney makes to urine production

Treatment of kidney stonesEven if complications of kidney stones are not obvious, their presence may contribute to the progression of chronic kidney disease (CKD). Since oxalate stones do not dissolve, treatment can be challenging for your pet and for your veterinary team.

Some urinary stones, your veterinarian may want to treat conservatively, with a combination of antibiotics, diet, and plenty of water. Dissolving kidney stones completely, often takes months, but any early reduction in size is a good start.

Medical efforts to dissolve kidney stones are usually safer than surgery, but wont work for all stones. Skilled surgery is widely available, but does risk permanently damaging the affected kidney, even if the surgery goes smoothly. Veterinary urologists can offer special techniques to break stones into smaller pieces so they can just pass out in the urine. This alternative procedure to surgery could offer a safe cure for kidney stones³.

For bigger stones, specialists might break them up from the inside using endoscopes and special tools. Its always fair to ask your doctor if a recommended surgery is the only option, or if there might be a cutting edge technology to try, instead.Monitoring and Management of kidney stonesIf your vet suspects oxalate kidney stones, she may suggest using diet and some medications to reduce or slow stone growth, with a significant emphasis on increasing water intake. A general strategy involves reducing mineral concentration to discourage crystal and stone formation. Increasing water intake makes the urine more dilute and should reduce the amount of mineral available to form a stone. A variety of diets have been used successfully to prevent or manage urinary stones, but finding the best fit for your dog could take some trial and error. These strategies are worth the effort, for sure, to try to avoid the pain and problems that a growing kidney stone may cause. If an underlying cause for stones is suspected, then resolving that problem will be another important way to protect those kidneys from more stone damage.

Even if the stones dont seem to be active or causing infection or blockage, regular monitoring of lab tests for kidney function and urine quality will continue to be important for the rest of your dogs life. Your vet will want to make sure that the prevention strategy is working, to see that the stones are not growing or causing complications. That evaluation will likely need some form of imaging rechecks, with either radiographs (x-rays) or ultrasound. If the stones were removed or treated medically, monitoring for their recurrence will be key to keeping your dog healthy. You and your veterinarian can determine the monitoring schedule that best matches your dogs condition. A stone-free dog is a happier and healthier pet.

If you have any questions or concerns, you should always visit or call your veterinarian -- they are your best resource to ensure the health and well-being of your pets.

Resources:

1. Low WW, et al. Evaluation of trends in urolith composition and characteristics of dogs with urolithiasis: 25,499 cases (19852006). J Am Vet Med Assoc. 2010;236:193200.
2. Jessica E Markovich and Mary Anna Labato, Medical Management of Nephroliths and Ureteroliths in JD Bonagura and DC Twedt ed Kirks Current Veterinary Therapy XV, Saunders Elsevier, St. Louis, 2014 PP 892-896.
3. Berent, Chick Weisse Interventional Strategies for Urinary Disease in Kirks CVT XV JD Bonagura dn DC TwedtElsevier Saunders St Louis 2014 PP884-892

Kidney Stone Diet: Foods to Eat and Avoid

You may be able to prevent kidney stones from forming with dietary changes, including staying hydrated, consuming more citrus, and avoiding certain foods like those high in sodium.

Kidney stones in the urinary tract are formed in several ways. Calcium can combine with chemicals, such as oxalate or phosphorous, in the urine. This can happen if these substances become so concentrated that they solidify. Kidney stones can also be caused by a buildup of uric acid. Uric acid buildup is caused by the metabolism of protein.

Your urinary tract wasnt designed to expel solid matter, so its no surprise that kidney stones are very painful to pass. Luckily, they can usually be avoided through diet.

If youre trying to avoid kidney stones, what you eat and drink is as important as what you shouldnt eat and drink. Here are some important rules of thumb to keep in mind.

Stay hydrated

Fluids, especially water, help to dilute the chemicals that form stones. Try to drink at least 12 glasses of water a day.

Up your citrus intake

Citrus fruit, and their juice, can help reduce or block the formation of stones due to naturally occurring citrate. Good sources of citrus include lemons, oranges, and grapefruit.

Eat lots of calcium (and vitamin D)

If your calcium intake is low, oxalate levels may rise. Its preferable to get your calcium from food, rather than from supplements, as these have been linked to kidney stone formation. Good sources of calcium include milk, yogurt, cottage cheese, and other types of cheeses. Vegetarian sources of calcium include legumes, calcium-set tofu, dark green vegetables, seeds, and blackstrap molasses. If you dont like the taste of cows milk, or, if it doesnt agree with you, try lactose-free milk, fortified soy milk, or goats milk. Also make sure to include foods high in vitamin D each day. Vitamin D helps the body absorb more calcium. Many foods are fortified with this vitamin. Its also found in fatty fishes, such as salmon, mushrooms, and cheese.

Limit salt

High sodium levels in the body, can promote calcium buildup in urine. Avoid adding salt to food, and check the labels on processed foods to see how much sodium they contain. Fast food can be high in sodium, but so can regular restaurant food. When youre able, ask that no salt be added to whatever you order on a menu. Also, take note of what you drink. Some vegetable juices are high in sodium.

Lower your animal protein intake

Many sources of protein, such as red meat, pork, chicken, poultry, and eggs, increase the amount of uric acid you produce. Eating large amounts of protein also reduces a chemical in urine called citrate. Citrates job is to prevent the formation of kidney stones. Alternatives to animal protein include quinoa, tofu (bean curd), hummus, chia seeds, and Greek yogurt. Since protein is important for overall health, discuss how much you should eat daily with your doctor.

Be mindful of oxalates

Eat oxalates wisely. Foods high in this chemical may increase formation of kidney stones. If youve already had kidney stones, you may wish to reduce or eliminate oxalates from your diet completely. If youre trying to avoid kidney stones, check with your doctor to determine if limiting these foods is enough. If you do eat foods containing oxalates, always make sure to eat or drink a calcium source with them. This will help the oxalate bind to the calcium during digestion, before it can reach your kidneys. Foods high in oxalate include:

• chocolate
• beets
• nuts
• tea
• rhubarb
• spinach
• swiss chard
• sweet potatoes

Dont drink colas

Avoid cola drinks. Cola is high in phosphate, another chemical which can promote the formation of kidney stones.

Reduce or eliminate added sugar intake

Added sugars are sugars and syrups that are added to processed foods and drinks. Added sucrose and added fructose may increase your risk of kidney stones. Keep an eye on the amount of sugar you eat, in processed foods, such as cake, in fruit, in soft drinks, and in juices. Other common added sugar names include corn syrup, crystallized fructose, honey, agave nectar, brown rice syrup, and cane sugar.

Having kidney stones increases your risk of getting them again unless you actively work to prevent them. This means taking medications prescribed to you for this purpose, and watching what you eat and drink.

If you currently have stones, your doctor will run diagnostic tests, to determine what type you have. They will then prescribe a specific diet plan for you, such as the DASH Diet. Tips that will help include:

• drink at least twelve glasses of water daily
• eat citrus fruits, such as orange
• eat a calcium-rich food at each meal, at least three times a day
• limit your intake of animal protein
• eat less salt, added sugar, and products containing high fructose corn syrup
• avoid foods and drinks high in oxalates and phosphates
• avoid eating or drinking anything which dehydrates you, such as alcohol.

Kidney stones are typically a painful condition. Fortunately, diet can be an effective tool in managing and preventing kidney stones. Staying hydrated and avoiding certain foods that are high in salt and sugar, and pairing calcium with oxalate rich foods are important elements of a kidney stone diet.