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. Several possibilities could have caused this problem, but the vet suspected urinary stones. Miniature Schnauzers are one of several breeds prone to 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 isn’t easy, but you can do it with 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. Several excellent reviews of canine urinary stones are available online.
The next question was the type of stone. Several chemical types 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 stones. The conclusion was that they were probably calcium oxalate.
There is a lot of good information online, but one reference I found especially useful is on this site. Dr. Ron Hines, DVM, maintains this website. I have found this to be the best source of information, mainly because Dr. Hines often goes back to the original research and clearly explains 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 that carries urine from the bladder to the penis). In dogs, this can cause a urinary obstruction because the urethra passes through a narrow, hollow bone (os penis) where stones can lodge and block urine flow. This creates an emergency which can be fatal if not corrected.
Surgery: 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 aren’t equipped to do it. We found a vet to do the surgery, and it was done in early November, 2014. Cosmo took about two weeks to recover fully. 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, the current strategy to prevent their return is to change the dog’s diet to create urine that is both more dilute (specific gravity less than 1.02) and less acidic (pH 6.6-6.8). Urine analysis at a vet office can be expensive, but you can easily check these two variables at home. One can use pH test strips and a refractometer for specific gravity. Both are easy to use and relatively inexpensive to buy on 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 recurrence is to use wet rather than dry food, and to choose one that is also low in oxalates. Wet food is mostly water (e.g., >75%), which dilutes the urine. Oxalates are fairly common in commercially available dog food because it is often formulated from soy and corn products. Low oxalate dog foods are available, such as Urinary SO (Royal Canin). Still, 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 you formulate such a diet? Several veterinary dietitian services are available (usually through vet schools), but they are 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
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…Â
Although it takes time to learn, the program proved invaluable. Using Pet Diet Designer, we developed the following diet, which, when combined with the commercial Urinary SO moderate calorie canned food, provides a complete diet that meets our goal of diluting his urine.
Recipe
Broccoli: 200g (from Costco mixed frozen Normandy vegetables)
Cauliflower: 200g (from Costco mixed frozen Normandy vegetables)
Carrots: 150g (from Costco mixed frozen Normandy vegetables)
Peas: 245g (frozen)
Turkey (ground, cooked): 532g
Beef (cooked 15% fat ground beef): 179g
Rice (cooked): 509g
Beef liver (cooked and chopped):98g
Egg (hard-boiled and diced): 161g
Canola oil: 17g
Kelp (Nature’s Sunshine): 1/2 capsule
Fish Oil (Costco 1 gram caps): 3 caps, cut
Bone meal powder: 13g
Tuna (small can in water): 85g
Mix the ingredients in a large bowl or pot, then freeze in Ziploc bags for later use. For Cosmo, we make a batch about every 10 days. The quantities and ingredients vary somewhat. For example, you can use chopped, cooked chicken instead of 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 many calories.
The PDD nutritional analysis for this batch of food (2393 grams) is shown in the links below. One simply enters the diet ingredients from the program’s database. The program then calculates the total calories (in this case, 1.22 calories per gram). Since the nutritional analysis covers multiple days of the diet (i.e., the batch), you need to scale the batch to get the correct daily amount based on Cosmo’s nutritional needs (about 560 calories per day). You can do this 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) provides only about 300 calories, but Cosmo requires about 560 calories per day (calculated by PDD based on his weight and lifestyle). We found it difficult to create a nutritionally complete homemade diet using only low-oxalate foods. We would have needed numerous supplements. Also, his urine did not seem as dilute if we used only 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 you enter the scaled quantities of the homemade food, along with the canned food, into PDD, it produces a complete dietary analysis that compares the recommended daily requirements with what the food provides. You can view the dietary report 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
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.
UPDATE (August 01, 2017): In spite of our dietary efforts, Cosmo has stones yet again. We took him in for his one-year post-surgical (surgery #2) check-up and an X-ray revealed a number of small stones identical in appearance to previous oxalate stones. Now, what to do? Change his diet yet again? Another surgery? Perhaps lithotripsy? Treat him with hydrochlorothiazide (a drug that can reduce calcium levels in the urine?Â
UPDATE (December 24, 2019): Cosmo had has last stone surgery in early February 2018 by a Tucson vet. This was his third cystotomy and he recovered quickly and without complications. Since then he has had his bladder checked every 6 months either by ultrasound or an x-ray and no stones have been found through August 2019. His diet has evolved somewhat over the years but is basically the same as described in other posts. It is low in oxalate, with added citrate (to make his urine less acidic) and with lots of fluid. We give him “soup” three times a day to maximize his fluid intake. The latter dilutes the urine so that calcium oxalate crystals are less likely to form. Most of his water is bottled to minimize its mineral content.Â
