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Cosmo's Urinary Stones - Part 1

Cosmo's Urinary Stones - Part 1

This is a description of our dog's (Cosmo, a male miniature schnauzer) urinary stone problem.... how the problem developed; what was done to remove the stones; and what we are doing to prevent their return. 

Symptoms: Cosmo was about 5.5 years old when our grandson noticed that his urine was red while walking him. He didn't seem to be in any distress, but a visit to the vet confirmed there was blood in his urine and that he had a urinary tract infection. There were several possibilities as to the cause of this problem, but the vet suspected urinary stones. Miniature Schnauzers are one of several breeds that have a propensity for developing this problem. Only an X-ray of his bladder could confirm their presence. Since the X-ray examination can be expensive (typically $75-$90 per image) we put that off until the course of antibiotics was complete.

We were able to buy urinary test strips from Amazon for a reasonable price and used these to test his urine for blood. Collecting urine from a dog is not all that easy, but can be done using a ladle. Only a small quantity of urine is needed for the test strip. Even after the infection was clear, the blood in his urine continued. The urine no longer looked like dilute cranberry juice, but the tests showed hematuria which indicated a persistent problem like stones. Subsequent X-rays confirmed their presence. There are several excellent reviews of canine urinary stones on the web.

The next question to be addressed was the type of stone. There are several chemical types that are known, but the two main ones are struvite (magnesium ammonium phosphate) and calcium oxalate stones. The former can often dissolve on their own with a change in diet, while the oxalate stones almost always need to be surgically removed. Cosmo's diet was changed for several weeks (vet recommended diet), but nothing changed. The hematuria eventually stopped, but the X-rays still showed the presence of stones. The conclusion was that they were probably calcium oxalate.

There is a lot of good information on the web, but one reference I found especially useful is found at this site. This website is maintained by Dr. Ron Hines, DVM. I have found this the best source of information mainly because Dr. Hines often goes back to the original research and provides clear explanations of the conclusions. Very well done.

Aside from causing urinary tract infections and bladder irritation, stones can be a special hazard in male dogs because they can pass into the urethra (the tube which carries urine from the bladder to the penis). In dogs this can cause a urinary obstruction since the urethra passes through a narrow, hollow bone (os penis) where the stones can lodge, blocking the flow of urine. This creates an emergency situation which can be fatal if not corrected.

Surgery: In order to remove the stones, the bladder must be opened surgically. This is not trivial surgery and costs from $1500 to $2000. Urinary stones are fairly common and most canine vets have experience with the procedure. Lithotripsy is also possible, but most vets are not equipped to do this procedure. We identified a vet to do the surgery and had it done in early November, 2014. Cosmo took about two weeks to fully recover. The stones were sent in for analysis which confirmed they were indeed calcium oxalate.

Diet: As mentioned above, certain dog breeds seem to develop these stones more frequently than others. Why they develop is a mystery and unfortunately they can reform. Generally speaking, the current strategy to prevent their return is by changing the dog's diet to create urine which is both more dilute (specific gravity less than 1.02) and less acidic (pH 6.6-6.8). Urine analysis by a vet office can be expensive, but is easily done at home for these two variables. One can use pH test strips and a refractometer for specific gravity. Both are easy to use and relatively inexpensive purchases from Amazon. It is important to see how the dog reacts to the diet change on an ongoing basis... daily checks for the first few weeks.

The basic strategy to help prevent the recurrence of stones is to use a wet rather than dried food and to use one which is also low in oxalates. The rationale for using wet food is that it is mainly water (e.g., >75%) which dilutes the urine. Oxalates are fairly common in commercially available dog food since they are often formulated from soy and corn products. Low oxalate dog foods are available, such as Urinary SO (Royal Canin), but they tend to be expensive (~$3 per 13 oz can, 326 calories for "moderate calorie") especially for a good sized dog. Cosmo, who weighs about 25 pounds (11.34 kilos) requires about 560 calories per day. The usual advice is to split the dog's food into at least two daily servings so that the effect on the urine lasts most of the day. Drugs can also be used to reach these specific gravity and pH goals, but diet is preferred if it works.

An alternative to commercially available foods is to make homemade food. But how should such a diet be formulated? There are several veterinary dietitian services available (usually through vet schools), but they are rather expensive and not inclined to give general guidelines for a homemade pet diet. However, we found a good starting point online for such a diet on the following site:


DogAware.com Articles: Calcium Oxalate Stones

The recipe we started with is toward the end of this article under "Sample Recipe." This article does provide some other useful information, but it is mainly from the experience of one individual with a limited number of dogs.

A great help in evaluating this diet, and determining an appropriate diet for Cosmo, was the software, Pet Diet Designer (PDD), which is available online at low cost... 

Although it takes some time to learn, the program proved to be invaluable. Using Pet Diet Designer we came up with the following diet, which when used in combination with the commercial Urinary SO moderate calorie canned food, gives a complete diet that meets our goals of diluting his urine.

The ingredients are mixed in a large bowl or pot and then frozen in zip lock bags for later use. For Cosmo, we make a batch about every 10 days. The quantities and ingredients vary somewhat. For example, chopped, cooked chicken can be used rather than turkey. Or you could use more hamburger and less chicken or turkey. The quantities can also vary... think cooking for humans! You don't need to be that precise. But keep track of what you use. We use a small kitchen scale to measure quantities in grams. Then you can use PDD to determine the caloric and nutrient content of your batch. As seen below, most of the calories are from the meats and rice. The vegetables add fiber and nutrients, but not a lot of calories.

The PDD nutritional analysis for this batch of food (2393 grams) is shown in the links below. One just enters the diet ingredients from the database found in the program. The program then calculates the total calories (in this case 1.22 calories per gram). Since the nutritional analysis is for multiple days of the diet (i.e., for the batch), the batch needs to be scaled to give the correct daily amount based on Cosmo's nutritional needs (about 560 calories per day). This can be done using one of the PDD reports as shown below. This report gives the batch amounts on the far right and the scaled amount in the column just to the right of the ingredients. In this case, I have scaled the amounts to 250g, which is the daily amount I typically use for Cosmo, divided over 2 meals. The report can be seen here.

Note that this amount (250g per day) only gives about 300 calories, but Cosmo requires about 560 calories per day (calculated by PDD from his weight and life style). We found that it was difficult to obtain a nutritionally complete homemade diet using low oxalate foods only. We would have had to use numerous supplements. Also, his urine did not seem to be as dilute if we only used the homemade diet. So we ended up using a combination of homemade food and the Urinary SO moderate calorie canned food (125g of homemade plus 80 grams of Urinary SO) per meal. With this combination, about 2/3 of his calories come from the homemade diet.

When the scaled quantities of the homemade food, along with the canned food, are entered into PDD, a complete dietary analysis can be produced which compares the recommended daily requirements with that which is provided by the food. The dietary report can be seen here.

A better representation of the daily diet is shown in this screen shot from the PDD which can be seen in the image below.

Here the percent of RDA is shown rather than the absolute quantity shown in the report. As can be seen, the diet provides sufficient quantities of essential nutrients with the exception of vitamin K which can often be obtained from gut bacteria.

This amount of food provides about 450 calories per day, which is still short of Cosmo's theoretical need of 560 calories. But we also feed him "soup for lunch" to increase his water intake during the middle of the day. This consists of 90 g of bouillon (chicken or beef) plus a small amount of rice or other scrap food. All in all, he ingests about 12 oz of water in his two main meals (we add 1 oz of water to the food at each meal), plus another 3 oz from the lunch soup. This is quite a bit of water per day... about 450cc. Plus he drinks some water as needed.

How much does this all cost? It is not cheap. One can buy Urinary SO (moderate calorie) for $2.50 to $3.00 per can not including tax. The caloric content is lower than homemade food (0.89 cal/g vs 1.22 cal/g) so one must feed more of the commercial food. The cost of supplying 450 calories per day from Urinary SO is about $4.15 at $3/can. And considering that the main ingredient is pork by-products, it is not something I would like to feed to Cosmo as his only food in the first place. The cost of homemade food is less per gram and it has about 1/3 more calories per gram as noted above. The cost of providing 450 calories using a mix of Urinary SO (160g/day) and homemade (250g/day) is about $2.65. A batch of the homemade food is shown below. We add the Urinary SO to each serving (not mixed). He always eats the homemade food first!

Cosmos Homemade Food

Snacks/Treats: Unfortunately, we have found that many dog treats contain ingredients which are high in oxalates. But we have found two snacks that Cosmo loves.... dried banana chips (Trader Joe or Amazon) and Beef Jerky. Both are low in oxalates.

We followed his urine specific gravity and pH for several months after he started on this diet around December 1, 2014. Both values vary somewhat throughout the day, but generally his urine is close to goal in specific gravity. As mentioned above, his urine pH is sometimes too low, but we have decided not to use drugs to raise it at this time. But the bottom line is, has he developed any more stones? We had X-rays taken 6 months after his surgery and his bladder was clear. We will continue to monitor his bladder for stones every six months. Cosmo loves this diet and seems to be doing well on it... nice coat and disposition. Well formed stool and regular. And he has maintained his weight on this diet. No problems that the vets can see either.

George and Cosmo at the vet

The original source of this article can be found at the following website: http://wp.geoandpat.com/wp/index.php/cosmo-bladder-stones/

UPDATE (November 08, 2015): Cosmo had his 12 month post surgical bladder exam (i.e., an x-ray) and there were no signs of stones. Very good news. The vet remarked that she thought that his diet was a key factor in halting the return of the stones.

Also, in August he had a lipoma removed and had some blood work done. Everything looked normal.

We continue to use the diet we developed months ago using PDD. So far he has been on it for about 10 months. There is some fluctuation from batch to batch, but nothing of significance (e.g., chicken rather than turkey meat). We make a new batch about every 10 days and keep it frozen until used. He really likes his food, his coat seems to be in good shape and his weight has been very steady.

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