Kidney, Bladder and Gallbladder Stones
- About Kidney, Gall and Bladder Stones
- Symptoms of stones
- How to diagnose stones
- Predisposing Factors that Create Stones
- Common Bacteria Associated with Stones
- Referred pain associated with kidney stones
- Related Stone Pages on this website
- Links References & Resources
Common Types of Stones:
- Ammonium Acid Urate
- Calcium Containing Stones
- Calcium Carbonate
- Calcium Oxalate Stones
- Calcium Oxalate Dehydrate
- Calcium Oxalate Monohydrate
- Calcium Pyrophosphate
- Calcium Phosphate
- Carbonate Apatite
- Cholesterol (Biliary)
- Magnesium Ammonium Phosphate (see Struvite)
- Octacalcium Phosphate Pentahydrate
- Silica and Silicate
- Struvite (Magnesium Ammonium Phosphate)
- Tricalcium Phosphate
- Uric Acid Urate and Dehydrate
What are Kidney Stones and how are they Formed? Kidney stones (also known as renal calculi, renal lithiasis, urinary calculi, urinary tract stone disease, nephrolithiasis, urolithiasis and ureterolithiasis) form from salts and minerals when the concentration of waste debris increase so much waste stagnates and sometimes surrounds a tiny nidus (nidus is Latin for “nest”) such as a bacteria or clump of minerals or amino acids. These tiny crystals in the urine clump around the nidus to form a solid mass or stone which just grows bigger and bigger if it is not discharged or flushed from the system. Stones are often formed in concentric circles or even in odd shapes as you will see in the pictures below.
Picture reference: https://byhealth.com/urinary-system
Urine is formed in the kidneys which are two fist-sized organs shaped like kidney beans near the middle of the back. Blood travels through the kidneys, where tiny networks of filters called glomeruli remove waste products and extra water. Each day, the kidneys miraculously process about 200 quarts of blood filtering out toxins and waste water from the blood to make urine. The water and waste form urine, which flows from the kidneys, into small tubes called ureters and into a holding chamber (the bladder) for eventual elimination by the body through the urethra.
Some stones may be tinier than a grain of sand so that they easily pass into the bladder and out into the urine but others can even get to the size of the entire bladder. These really hurt and need to be surgically removed. If small stones get stuck in the ureter, this can cause excruciating pain and infection which can lead to permanent kidney damage.
Researchers say about 12 percent of American men and 5 percent of women develop a kidney stone in their lives. Some people have more than one episode. The reason why men develop more stones is because their urethra is smaller than a woman’s. Women produce stones and sand too, but they pass more easily through the plumbing system.
Male dogs, sheep and goats have a challenge because they have a bone within the penis (called the os penis) and stones get caught in this area.
If you do go to the Emergency Room to be diagnosed make sure you follow up with a specialist instead of ignoring the problem. Kidneys are vital organs and if you are experiencing pain in them you need to be seen and treated appropriately.
Symptoms of Kidney and Bladder Stones include:
- Severe pain or aching in the back on one or both sides
- Sudden spasms of excruciating pain (renal or uteric colic) usually starting in the back below the ribs, before radiating around the abdomen, and sometimes to the groin and genitalia (see diagram for referred pain because referred pain is often missed
- Bloody, cloudy, orange or smelly urine
- Burning sensation during urination
- Chronic urinary tract infections
- Disorientation and fatigue
- Dull pain in low back (often for days)
- Feeling or being sick
- Fever and chills
- Frequent urge to urinate (polakyuria)
- Loss of appetite
- Nausea with possible vomiting (like having the flu)
- Pain in stomach, back or groin (sometimes severe agony compared to the pangs of natural childbirth which responds only to some severe pain medication)
- Straining to urinate (we call it stranguria) or difficult urination (dysuria)
These can also be symptoms of a urinary tract infection, or cystitis, which is much more common than kidney stones in young patients, especially women. If you have one or more of these symptoms you should seek medical advice so the proper tests can be performed to diagnose the problem. (See my handout on Urinalysis Interpretation under Health Basics).
Kidney stones are usually passed out of the body within 48 hours, but attacks can sometimes last for over 30 days.
The types of kidney, gall or bladder crystals or stones that humans or animals produce depends on their diets, anatomy and predisposing factors which will be discussed below:
Predisposing factors for Stone Formation (Who gets kidney stones?)
- Abnormal urinary pH: Some stones and crystals form in acid urine and some in alkaline. Please review the individual stones and crystals listed and described below to determine which crystals you may be diagnosed with depending on urinary pH. Also see the handout on the basic Urinalysis.
- Allergies: Some allergies are known to be associated with an increase in stone formation.
- Avoid L-Cysteine if you have a genetic disposition to stones.
- B Vitamin and Magnesium Deficiency: See the associated charts to see if you have any deficiency symptoms.
- Cadmium: High levels of the heavy metal cadmium in the body can increase the incidence of kidney stones.
- Calcium Supplements: Those who take too many or the wrong type of calcium supplements
- Chemotherapy: Can cause and increase in the number of uric acid crystals seen in the urine sediment.
- Chronic UTI’s: Those with chronic urinary tract infections.
- Cystinuria: In cystinuria, the kidneys produce too much of the amino acid cystine. Cystine does not dissolve in urine and can build up to form stones. (Rare inherited disease.)
- Dehydration: is a major cause of stone formation. In the winter we are not wanting cold foods and our pet’s water dishes sometimes freeze over.
- Drug Overdose: Increases the saturation of metabolites in the urine.
- Diabetes: Too much urination dehydrates the body concentrating the minerals and other substances responsible for forming the center (nidus) of stones.
- Essential Fatty Acid Deficiencies: You need fats of specific kinds to draw minerals into the cells of the body.
- Excess Sugar: Sucks the minerals out of the bone and into the kidneys/urine.
- Genetic Predisposition in Animals: Some breeds of animals are more predisposed (see Breeds Predisposed to Stones handout)
- Genetic Predisposition in Humans: People and animals genetically predisposed
- Gout: People with gout normally excrete more stone metabolites through their urine.
- Having very poor mobility (eg, those being confined to bed)
- Heavy Metal Poisoning: Excess aluminum
- High Ash Diets: Especially cheap animal diets
- High Oxalic Food Diets: See High Oxalate Foods List
- Hypercalciuria: Absorptive hypercalciuria occurs when the body absorbs too much calcium from food and empties the extra calcium into the urine. This high level of calcium in the urine causes crystals of calcium oxalate or calcium phosphate to form in the kidneys or urinary tract.
- Hyperoxaluria: With hyperoxaluria, the body produces too much of the salt, oxalate. When there is more oxalate than can be dissolved in the urine, the crystals settle out and form stones. (Rare inherited disease.)
- Hyperurcosuria: A disorder of uric acid metabolism, gout, excess intake of Vitamin D or a blockage of the urinary tract causes this metabolic syndrome. Certain diuretics (water pills) or calcium-based antacids may increase the risk of forming kidney stones by increasing the amount of calcium in the urine.
- Hypoalbuminemia: Too little protein in the blood
- Hypocitraturia is seen in renal tubular acidosis (especially of the distal RTA type I), chronic diarrhea and in excessive animal protein intakes. Many bacteria infecting the urinary tract reduce the citrate concentration which can lead to crystals in the urine.
- IBD & Intestinal Bypass: People with Inflammatory Bowel Disease or those who have had intestinal by-pass surgery
- Kidney Malformations: Those with kidney disorders like cystic kidneys, having only one kidney, or those with an abnormally shaped kidney.
- Medications: Taking certain medicines such as diuretics (water tablets), antacids and thyroid medications. See List of Drugs Associated with Stones.
- Men are more prone than women especially between the ages of 20-40 years of age
- Metabolic disorders like: Cystinuria, Hyperoxaluria, Hypercalciuria, Hyperurcosuria, and Hypocitraturia
- Overuse of Aspirin
- People who have been catheterized for long periods of time
- Previous History of Stones: About half of all people who have previously had a kidney stone will develop another one within five years.
- Red meat: Too much red meat (high Protein diets) imbalances the calcium/magnesium/phosphorus in the system.
- Salt Intake: Too much salt in the diet
- Some medications: See the Stone Handout for a list of those meds.
- Too much Alcohol: Avoid alcohol of all kinds if you are a stone former. Alcohol increases the excretion of uric acid, calcium and phosphate which puts more strain on the kidneys.
- Too much caffeine: Draws minerals from the body and acts as a diuretic.
- Too much Soda Pop: Imbalances the calcium/magnesium/phosphorus in the body.
- Too much Vitamin D: Animals and people who have been overdosed with too much Vitamin D
Common bacteria associated with bladder stones include: Ureaplasma urealyticum, U urealyticum, Proteus mirabilis, Staphylococcus, Klebsiella, Providencia, Pseudomonas, and Staphylococci which are all urease-producing enzymes that result in the production of many struvite crystals.
Nanobacteria can also cause stones, but carbonate apatite ones. Nanobacteria is hard to diagnose as a core cause of kidney stone formation because they are about the size of a virus, don’t grow as quickly as the other bacteria listed above and don’t grow well on the media they normally use in the lab to culture out bacteria. Nanobacteria is best treated with Tetracycline at this point, but researchers are trying to find alternatives to this drug.
Kidney Stones: Depending on where they are located, kidney stones are also known as renal calculi, urinary calculi, urinary tract stone disease, nephrolithiasis, urolithiasis and ureterolithiasis.
How are kidney stones diagnosed?
Doctors can usually diagnose kidney stones by asking about your symptoms and examining you. Further tests may be done to confirm the diagnosis and to reveal the size, location and type of stone. These include:
- Blood tests – to identify excess amounts of certain chemicals related to the formation of stones . Lab Test Result Interpretation
- CT Scan (Non-contrast helical computerized tomography) – this produces pictures from a series of x-ray images taken at different angles – it is sometimes used to diagnose kidney stones, and is thought to be the most accurate diagnostic test.
- ECG– Can show heart rate and rhythm abnormalities if the stones are caused by an increase in certain minerals (but this choice of diagnostic technique would not be common).
- Imaging techniques which involve an injection of a special dye that shows up the whole urinary system on x-ray images, revealing stones that can’t usually be seen. Examples are:
- Excretory urography – where a contrast agent is injected into the blood stream and is then cleared by the kidneys, outlining the kidney, ureters and urinary bladder.
- Renal angiography – where contrast agents are injected into the renal artery to assess the blood flow to the kidney.
- Retrograde urethrocystography – where contrast agent is injected into the urethra to outline the urethra and urinary bladder.
- Taking an x-ray image – stones that contain calcium usually show up white on x-ray images while other stone are translucent (radio-opaque which means you need additional tests).
- Ultrasound scan – this uses high frequency sound waves to produce an image of the internal organs.
- Urinalysis – to look for signs of infection, crystal formation, determine ph (see urinalysis handout.)
Most Common Types of Stones:
Pictures from www.Herringlab.com (Here are just a few!)
Ammonium Acid Urate: These stones are common in the Dalmatian.Urate stones once present can cause “secondary” urinary infections where none existed before and the infection, in turn, can then complicate the diagnosis.
Brushite: Brushite stones (calcium hydrogen phosphate) develop in acid urine with pH values between 6.5 and 6.8 and in urine that has high concentrations of calcium and phosphate. When the pH value increases up to 6.8, Brushite converts into carbonate apatite. Brushite stones grow rapidly and return often if everything is not “just right.” Strong prophylactic treatment is very important in Brushite stone-formers. Brushite stones are very hard, therefore disintegration by lithotripsy is difficult to attain.
Calcium containing stones are the most common type of kidney stone. They are either spiky or large and smooth, and are made up of calcium oxalate or calcium phosphate. Calcium stones are more common in people who have excess levels of vitamin D or who have an overactive parathyroid gland.
Note: Uh, please note this because recently there has been a rash of advertising that everyone is low in Vitamin D and Vitamin D supplements are being prescribed like crazy. If you need it, you need it, but if you don’t then your body has to get rid of the excess. People who have medical conditions such as cancer, some kidney diseases, or a disease called sarcoidosis are also more likely to develop calcium stones.
Calcium Carbonate (Crystal in urine sediment) Also called calcite, is in limestone, dolomite and marble. Some calcium supplements contain this type of calcium. It’s best to take calcium supplements that are suited for your particular body type. Calcium carbonate stones are exceptionally rare. A previous analysis of a small number of pediatric gallstones from the north of England showed a remarkably high prevalence of calcium carbonate stones. Calcium carbonate stones were more common in boys, and almost half had undergone neonatal abdominal surgery and/or required neonatal intensive care. (Reference: https://www.ncbi.nlm.nih.gov/pubmed/17923195)
One source I read suggested a core cause of liver disease. Calcium Carbonate stones are common in guinea pigs and rabbits. I suspect it may be from feeding too much alfalfa to these critters.
Calcium Oxalate Stones (Note how they look different—this is why we need to have the lab test them to see what kind they are.) See Also: Urinalysis on Calcium Oxalate (Hippurate).
Some conditions predisposing to Calcium Oxalate Crystals include:
- Addison’s Disease
- Some types of cancer
- Cushing’s Syndrome
- Primary Hyperoxaluria (a rare genetic disease).
- Pyridoxine Deficiency (/Diet_Nutrition/vitamin_b6_pyridoxine.htm ).
- Increased Intestinal Absorption of oxalates. Here, fatty acids are competing with oxalate for the intestinal calcium. In fat malabsorption, the increase of unabsorbed fatty acids mobilizes the calcium leaving the oxalate, free to be absorbed. Intestinal calcium limits the absorption of oxalate. Some drugs can be given to prevent this from happening See Allopathic Medical Treatment of Stones link below.
Calcium oxalate crystals form in acid to neutral urine and are the most common stones in male dogs. These crystals can be smooth, rough, speculated or jackstone in shape. The jack shape is really weird and must hurt like a son-of-a-gun!
If you see calcium oxalate crystals in the urine, be sure to run additional tests to check for the diseases listed above. These crystals don’t dissolve and must be surgically removed and are very visible with radiography.
They can be prevented with low protein and low oxalate diets (See High Oxalate Food List Link below) and diets with higher amounts of magnesium, phosphorus (which prevents the calcium from dumping into the urine). Also, more dietary calcium helps reduce the absorption of calcium oxalate from the intestine. Complicated stuff. The addition of potassium citrate and thiazide diuretics have also been shown to help with oxalate uptake. (See Medical Treatments for Stones Handout—link below.)
Calcium oxalate – the most common type of stone. Can be due to excess amounts of calcium or oxalate in the urine. These stones come in two different types –calcium dehydrate and calcium monohydrate:
Calcium Oxalate Dihydrate (Also called Weddellite) breaks easily with lithotripsy.
Calcium Oxalate Monohydrate (also called Whewellite) these are really tough stones and do not break up with lithotripsy.
These type of stones are often in people and animals that have a diet high in oxalates (See list of High Oxalate foods.) They cannot be dissolved. Calcium oxalate crystals are more common in Europe than in the United States.
Treatment and Prevention of Calcium oxalate stones:
- Increase fluid intake since it helps to dilute urine. Stay away from fruit juices, barley water, coconut water and lime juice.
- Avoid high protein diets.
- Restrict calcium intake. Foods that are high in calcium are most likely high in phosphorus.
- Stay away from High Oxalate Foods (see that list).
- Avoid vitamin and mineral supplements unless specifically prescribed.
- Avoid too much Vitamin C and Calcium-containing Antacids.
- Avoid vegetables and fruits containing seeds (e.g. Tomatoes, peppers, watermelon, guava).
- Restrict sodium intake.
- Add potassium citrate to diet to achieve a neutral or slightly alkaline urine.
- Increase Vitamin B6 in diet (See /Diet_Nutrition/vitamin_b6_pyridoxine.htm Food List).
- Possibly take a diuretic.
Calcium Pyrophosphate: Calcium pyrophosphate deposition disease (CPDD) is a metabolic disease which affects the joints resulting from the deposition of calcium pyrophosphate dihydrate (CPPD) in and around joints, especially in articular and fibrocartilage.
Although CPDD often is asymptomatic with only radiographic changes (ie, chondrocalcinosis), various clinical manifestations may occur, including acute pseudogout and chronic arthritis. Although almost any joint may be involved, the knees, wrists, and hips are most commonly affected. This condition is the most common cause of secondary metabolic osteoarthritis.
Canine Gout is a rare form of Gout and it is often diagnosed as calcium circumscripta
(Calcium Gout) or calcium pyrophosphate-dehydrate disease, which is a chalky liquid that can ooze from a dogs paws or from surgical interference. It can also appear as lesions on the paws of larger dogs.
Treatments and Prevention for Calcium pyrophosphate stones:
- Liver Support diets
- Colchicine (which can kill a dog if they eat the human version )
- Low Purine diets
- Increasing whole grains in the diet (but without the addition of yeast.)
Calcium phosphate (also known as Hydroxyapatite) stones are formed in neutral to alkaline urine and are usually smooth and round. This is rarely a pure stone and is often found combined with calcium oxalate and struvite. Dogs predisposed to this type are Yorkshire Terriers, Miniature Schnauzers and Cocker Spaniels. Core cause suspected includes metabolic disorders resulting in too much calcium being excreted into the urine. These must be surgically removed. You can prevent more from forming by acidifying the urine, feeding a calculolytic diet and preventing too much calcium from being excreted into the urine.
Carbonate Apatite: Two different kinds of calcium phosphate stones occur depending on the urinary pH value. Carbonate apatite stones develop in alkaline urine (pH > 6.8) with high calcium and low citric acid concentrations.
Cholesterol (Biliary): The incidence of gallstones is one million new cases per year and includes 20 million cases among Americans. Mexican Americans and several American Indian tribes, particularly the Pima Indians in the Southwest, have very high prevalence rates of cholesterol gallstones. Decreased bile acid secretion is believed to be the common denominator in these ethnic groups. The formation of gallstones usually starts after the age of 40.
(Reference: https://www.emedicine.com/MED/topic225.htm )
Cystine (Crystals in urine sediment and stones which may or may not show up in an X-ray.)
Cystine stones are yellow and crystalline and form in acidic to neutral urine and are usually round and smooth. Only one in a hundred kidney stones in the human are caused by this condition. Cystine stones tend to develop earlier in life than other kidney stones, usually between the ages of 10 and 30 years. This type of stone cannot be dissolved and needs to be surgically removed.
They are caused by an increased urine excretion of cystine and are a result of renal tubule reabsorption of cystine (inherited renal tubular transport defect of cystine).
Treatment and prevention includes surgery, decreasing dietary protein and alkalizing the urine. The pH of the urine should be kept above 7.5. Medications used to help dissolve these crystals by alkalizing the urine include potassium citrate, D-penicillamine, and 2-PMG.
Cystinuria is inherited and is a recessive trait in Newfoundlands. In other breeds it is sex linked and found primarily in male dogs. Dog breeds predisposed are Bulldogs, Dachshunds, Basset Hounds, Chihuahuas, Yorkshire Terriers, Irish Terriers and Newfoundlands.
Magnesium Ammonium Phosphate (See Struvite below)
Octacalcium Phosphate Pentahydrate: I’d never heard about this one in vet school, but it is a combination stone containing calcium and phosphate. I thought the picture was kind of cool so included it. There are really all types of different stones with combinations of minerals. Each stone needs to be sent to the lab where it is crushed and the components identified so that a treatment protocol can be formulated. It kind of looks like a fossil, doesn’t it? Infections may be part of the cause of this particular stone type.
Males produce 73% of the calcium oxalate stones. This stone type is unusual in females. Breeds at especially high risk include: miniature Schnauzer, Lhasa Apso, Yorkshire terrier, Miniature Poodle, Shih Tzu, and Bichon Fries’. Most cases occur in dogs between ages 5 and 12 years of age. Studies have shown that 50% of dogs that have undergone such surgery will develop new calcium oxalate stones within three years.
Calcium oxalate stones do not dissolve over time by changing to a special diet (as can be done with struvite or uric acid bladder stones). After the stones are removed, judicious therapy is adhered to for the prevention of future stones.
Core Causes of Oxalate Stones: Some people and animals have a genetic predisposition that prevents the production of enough substance called nephrocalcin in the urine. Nephrocalcin helps to naturally inhibit the production of calcium oxalate stones.
Some foods in the human diet exacerbate this genetic predisposition. These foods include: peanuts, spinach, Vitamin C supplements, chocolate, dairy products, calcium supplements and tea. These foods would also cause problems in predisposed breeds but these foods are not commonly incorporated into pet commercial diets.
Medications which can increase the risk of calcium oxalate stone development:
- Furosemide (brand name: Lasix) is a diuretic mostly used in the treatment of heart failure which also leads to excess calcium in urine. Should a diuretic be needed for a patient at risk for calcium oxalate stones, one from the thiazide class would be a better choice.
- Supplements with Vitamins D, Vitamin C or Calcium
Note these supplements and medications should be discontinued for people and animals predisposed to this type of stone.
Treatment and Prevention of Oxalate Stones:
While special diets cannot dissolve existing stones, they do help prevent the development of new stones. The goal is to create a urinary environment with minimal calcium and oxalates in a urine pH that is not conducive to stone growth.
Commercial diets for the dog that achieve this goal include:
- Science Prescription Hills k/d or u/d diets
- Select Care Modified diet
- Purina CNM NF Diet
- Waltham’s Low Protein Diet
Canned forms are preferable to dry because they have more water in them and you really need to keep the person or pet hydrated and the urine dilute to keep the components of the stones flushed out of the system. It’s really difficult to convince pet owners that they shouldn’t give (unbalanced) treats to their pets. So:
Acceptable treats for oxalate stone forming dogs:
- Plain Cooked Chicken
- Plain Cooked Turkey
Note: Many pet owners ask if any non-prescription diets are appropriate for this condition. None are.
So, what does one do after having the stones surgically removed? The specific step-by-step protocol is presented in the link below, but here is a summary of the general steps:
Two to four weeks after surgery, check the urine. If the urine is not adequately dilute, water consumption will have to be increased (either by adding water to the food or increasing the amount of canned food).
If urinary pH is less than 6.5 or if oxalate crystals are seen, add in potassium citrate. By taking potassium citrate orally, citrate levels increase in the urine. Calcium binds to citrate instead of to oxalate which is a desirable event since calcium citrate tends to stay dissolved whereas calcium oxalate tends to precipitate out as mineral deposit. Potassium citrate also helps create an alkaline urine (in which calcium oxalate stones have difficulty forming). Potassium citrate supplements are typically given twice a day.
If all is well, a urinalysis should be performed every two months or so for the rest of the dog’s life (University of Minnesota’s current recommendation). If you are unable to stabilize the urinary pH, then a thiazide diuretic is added to keep the urine dilute. This medication is typically given twice a day and electrolytes are generally measured via blood test within the first two weeks of this treatment.
Radiographs are taken every 3-6 months to identify any new stones. It is assumed that by taking an X-ray within this time span one will identify the stones as small enough to be retrieved from the bladder by flushing. If one skips this monitoring, stones present may develop to a large size which means another surgery to remove them.
Silica and Silicate
Silicate stones form in acid to neutral urine. They usually have a jackstone shape. Diets high in corn gluten or soybean hulls predispose the German Shepherd, Golden Retriever, Labrador Retriever and Miniature Schnauzer to this type of stone. Of course this type of diet is not good for the skin either! These stones cannot be dissolved.
Treatment and Prevention include:
Urine alkalinization and diets with low amounts of silicates.
Note: Foods high in silica include: Beer, beets, bell peppers, brown rice, leafy green vegetables , root vegetables, seafood, soybeans and whole grains.
Struvite Stones and Crystals:
100% magnesium ammonium phosphate hexahydrate (stone) This stone measures 35mm long (1.5 inches).
Struvite stones (Also known as infection stones, Magnesium Ammonium Phosphate)
Struvite crystals form in neutral to alkaline urinary pH and are often the result of bacterial urease-producing bacteria in dogs and humans. This bacteria is not usually present in cats.
Stones vary in size and shape and can assume the shape of the bladder or urethra and become quite large.
They develop when there is too much ammonia in the urine and can be seen upon routine urinalysis. This can happen if you have a urinary tract infection (UTI), because the urease enzyme producing bacteria generate ammonia. This kind of kidney stone is most often found in women.
Treatment and Prevention of Struvite Stones: To dissolve the crystals an acidified, low-protein diet is needed. We usually use Science Diet S/D (Struvite Diet) at first for about 6 weeks then change to a bit less acid diet like Science Diet C/D (Calculi diet) because the body can’t handle acid diets for long periods of time. There are now other prescription diets that accomplish the same goal.
These special diets have less protein, phosphorus and magnesium and more salt in them to stimulate thirst. These are not good diets to use in animals and people who suffer from heart failure, liver failure, kidney failure, pancreatitis (they are a bit high in fat), high blood pressure and those who have lower serum albumin in their blood.
Struvite Notes: The core cause of these stones are thought to be from the bacteria Staphylococcus aureus and possibly genetic core cause. You can see the stones with X-ray and the crystals with a urinalysis; they can be dissolved or surgically removed. These are the most common crystals and stones found in the dog and cat.
Tricalcium Phosphate with Apatite (Stones can be a mixture of two types of substances and are then called mixed composition stones. But stones formed in acid urine can’t mix with stones formed in alkaline urine.)
Uric Acid and Urates: Uric acid stones are smooth, brown and soft. Urate crystals which include ammonium urate or sodium urate monohydrate form in acidic to neutral urine. They are caused by in increased excretion of uric acid. There is genetic predisposition to having these types of crystals. Uric Acid stones cannot be dissolved. Excess amounts of uric acid can be caused by:
- Eating a lot of meat (high protein diets)
- Liver disease including portosystemic shunts which increases excretion of extra uric acid into the urine and
- High Blood Urea Nitrogen (BUN)
Treatment and Prevention of Uric Acid Stones:
- Reduce purines in the diet (basically gout-safe foods)
- Low Protein Diets: Urate stones can be prevented in 80% of dogs and 95% of cats.
- Science Prescription diet u/d can be used to prevent stone formation in the Dalmatian because it alkalizes the body.
- Increase fluid intake.
- Give allopurinol, a drug that helps prevent the formation of uric acid. Note: Allopurinol should not be given to cats. It can also cause xanthene stones.
Uric Acid stone and crystals in urine sediment seen under special lighting
This image provides a good example of uric acid. These crystals can take multiple forms: “A” is one of the rhombic plate (diamond-shaped) and is very common. “B” is the uric acid crystal in the shape of a barrel. They are often yellow to orange-brown in color. Under polarized microscopy they exhibit birefringence and many colors.
Uric Acid Dehydrate (Crystals in urine sediment)
Xanthene or Xanthine stones are very rare and are caused by an inborn defect of xanthine oxidase (something involving nitrate degradation). Drug therapy to dissolve xanthine stones is not available.
Treatment and Prevention of Xanthene stones includes:
- Drinking lots of fluids to dilute the stones out.
- An ovo-lacto-vegetarian diet to increase the urinary pH value and to decrease xanthine excretion is also indicated.
- A low-purine diet.
Referred pain from Kidney Stones: Referred pain is defined as pain that originates in one part of the body, but is felt in another part of the body. Pain in the shaded areas may be caused by a kidney stone. Referred pain is kind of a tricky area because the practitioner and patient both are looking for something specifically wrong in that area and they can’t find anything. I’m including this diagram because often you’ll have to determine on your own that it is a referred pain from another cause and not a primary pain caused by injury.
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