Calcium and Bladder Stones

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Post   » Sun Oct 20, 2002 7:56 pm

Dawn Hromanik gave me permission to reprint a letter she recently posted to the bladder stone mail list. For those of you who have guinea pigs diagnosed with stones, you may be interested in subscribing to this list and getting support from other pet owners who have gone through the same thing. Some of our current members post on this list.

Letters are sent to . I´m hoping someone will give me the correct address to sign up for this site if this is the wrong one and only used for replying to the mail list. Tex also has a page with links to articles on bladderstones in other animals:

A recent poster was surprised to see how much calcium there is in timothy pellets [a popular Oxbow Hay Company product for older pigs and pigs with specific medical problems]. She wondered if people dropped all pellets (including timothy) from the diet of pigs diagnosed with stones. Dawn´s letter addressed the importance of calcium in the diet and some of the causes of stones.

I know some of you have pigs diagnosed and treated for bladder stones. I encourage any of you to add information you have gathered and share it here.


Calcium is a very important part of a guinea pigs diet, and any living animal (including humans), however a diet too high in calcium is not good either for guinea pigs. It can be very dangerous, health wise, to eliminate all foods that do not contain calcium. If you do achieve this then your diet is much too high in phosphorus and the Calcium phosphorus ratio is inversed and other health problems occur. One that comes to mind is bone demineralization, primarily in the jaw, which can lead to dental (molar) problems.

Dietary calcium is only one part of the stone sludge problem in guinea pigs. (There are 5 main causes of uroliths, or stones in animals) Low water consumption I feel is the biggest contributor and many vets tend to agree.
A low water intake will concentrate the urine letting the calcium precipitate out and crystallize. Getting your guinea pig to drink more water would be a first step. Many guinea pigs if given a choice between plain water and water with Vitamin C added will choose the plain water. A guinea pig should drink 100 ml water/kg of body weight. A little less if they are getting a lot of greens, but even with greens being 95% water imagine how many greens it would take to equal 10 ml of water (hint 1 ml H20 3D1 gm, greens 95% water so working backwards it would take at least 100 grams of greens or about 1/4 of a lb of romaine per day. WHOA that´s a lot!!)

But before you can even speculate on a cause the stone has to be analyzed for composition and the nidus (center or nucleus) of the stone determined. The matrix of the "body" of the stone will almost always be calcium carbonate 99.9% of the time. I have not heard of a matrix that was not made up of calcium. This is because that is the environment that the stone was bathed in while in the bladder is calcium carbonate. It is the nidus that is important. That is the seed.

Calcium oxalate, phosphate, or the most prevalent carbonate can all be in the nidus. There is some significant data on oxalate stones in guinea pigs (and humans) that show a lack of an anaerobic bacteria oxalbactor formagenes (sp?, paper at work) predispositions GPs and humans to oxalate stones. The lack of this oxalate degrading bacteria in the cecum could also be responsible for some guinea pigs that have a "sensitivity" to high Ca greens where other rabbits have no problem. But I digress.

Another thing to remember, is it is not just the calcium level but the ratio of calcium to phosphorus. The rule of thumb that I use is that all vegetative parts of plants have a higher Ca:Ph ratio. This is ideal, you do *not* want the inverse where the phosphorus is higher than calcium. (this can attribute to phosphate stones and bone demineralization) Phosphate crystals embed themselves in the bladder wall and are very irritating. Reproductive parts of plants (seeds and roots) have a higher Ph content. This includes all fruit (apples, bananas, grapes, raisins), seeds (treat mixes, sunflowers, oatmeal etc), and carrots. Just another reason not to feed the above food.

I could go on about this topic, it has been one of my "pet" projects for the past several years and I have a vast bibliography on the topic. Dr. Carl Osborne has probably written the most on the subject of urinary calculi, and he even says that there are a lot of questions left unanswered.

Dawn Hromanik
Nutritional Director
Oxbow Pet Products
Last edited by Lynx on Thu Apr 03, 2003 8:23 pm, edited 2 times in total.

I GAVE, dammit!

Post   » Sun Oct 20, 2002 8:11 pm

The stones mailing list is an excellent resource.
I do believe the address is right.

Archived posts are very helpful for newly diagnosed pigs.
Last edited by Julian on Sun Oct 20, 2002 8:19 pm, edited 1 time in total.

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Post   » Fri Nov 08, 2002 4:23 pm

Dawn recently remarked that there is FREE testing of bladder stones by the University of Minnesota College of Veterinary Medicine -- Urolith Center. I don't know how long this free analysis is available, but click on the link to see if it is still active.

They are using the information related to each urolith case for epidemiology studies.

Urolith Center

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Post   » Mon Feb 28, 2005 10:35 am

Note, Belinda wrote me that the Oxalobacter formigenes (Bacteria) Dawn mentions can be found here:

(German company supplying laboratories -- DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH, Braunschweig, Germany)

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