Uric Acid, What It Is, How It's Formed and What Happens If It Accumulates In The Body

[egyptiandan]

From Mader's book "Reptile Medicine and Surgery"

Uric acid doesn't combine with calcium, so doesn't make stones. When uric acid is accumulated in the body it tends to combine with sodium forming crystals called "tophi". These either accumulate in the joints (periarticular gout) or the soft tissues (visceral gout).

Danny

 

[Madkins007]

I feel like I am missing something here- is this an argument against the idea that calcium supplementation can cause bladder stones or something?

 

[egyptiandan]

No Bladder stones are calcium.

Just trying to inform what exactly uric acid is and the fact it doesn't cause stones in tortoises.

Danny

 

[Torty Mom]

Danny awesome info, but now I am so confused. The vet is the one that said they are urate stones and not bladder stones. So, does this vet NOT know what she is talking about? The xray shows all those stones all through her intestines, what are those? Her bladder is clear, nothing in it.

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Danny what about this:

Calcium oxalate stones

Calcium oxalate stonesCalcium oxalate stones form in an acidic to neutral urine. Two types naturally occur, calcium oxalate monohydrate, or whewellite (CaC2O4·H2O), and calcium oxalate dihydrate, or weddellite (CaC2O4·2H2O). Their appearance can be rough, smooth, spiculated, or jackstone. Calcium oxalate stones form more readily in animals with hypercalcaemia, which can caused by Addison's disease or certain types of cancer. Hypercalcaemia results in hypercalciuria, which can also be caused by Cushing's syndrome or hyperparathyroidism.

There is no recommended diet to dissolve calcium oxalate stones. For prevention a diet low in protein and oxalates and high in magnesium, phosphorus, and calcium is recommended. Increased dietary magnesium and phosphorus decreases the amount of calcium in the urine, and increased dietary calcium reduces absorption of oxalates from the intestines.[7] Potassium citrate has been recommended as a preventative for calcium oxalate stone formation because it forms a soluble complex with oxalates and promotes the formation of alkaline urine.[2]

Dog breeds possible prone to calcium oxalate stones include Miniature Schnauzers, Lhasa Apsos, Yorkshire Terriers, Miniature Poodles, Shih Tzus, and Bichon Frises.[6] They are the most common stone in male dogs.[7] Calcium oxalate stones are also common in domestic rabbits. Rabbits are prone to hypercalciuria due to intestinal absorption of calcium not being dependent on vitamin D and a high fractional urinary excretion of calcium.[8] The urine will appear thick and creamy or sometimes sandy. Small stones and sand can be removed using urohydropropulsion. Prevention is through reducing calcium intake by feeding more hay and less commercial rabbit pellets, and by not using mineral supplements.

Could this be a possibility?

 

[kbaker]

This is confusing to me, too. More calcium/less calcium. It just sounds like a vicious cycle out of balance.

Danny-Thanks for the text book version...can you think of a way to explain it in simple terms for us?

 

[Balboa]

Thanks Dan! That's a helpful read! I'll try my layman's best to clarify some of this for others, but may make some misstakes.

1. To those confused by the origin of this post. I THINK it goes back to Silverstar's thread about his tort passing stones.
http://www.tortoiseforum.org/thread-21807.html
Which also happened to inspire my "any greens high in calcium, low in oxalates thread"

2. Danny's point is that urea doesn't form stones. Excess proteins can result in excess urea in the blood, which rather than forming stones in the bladder or kidneys, apparently is more likely to form crystals in the body. WHen these crystals form in joints it can lead to a form of arthritis called gout. This condition is likely heightened by dehydration (a classic, and chronic problem in captive torts), as sufficient hydration leads to frequent peeing too flush out the urates.

The weakened state or "depression" many captive torts are in may be in part a result of this condition. If it hurts to walk, a tort won't walk, which leads to further problems. They won't take the time to walk to the water bowl and drink (furthering the dehydration), they won't thermoregulate enough (which leads to poor digestion or poor hydration as they either stay too cool or too hot, and possibly poor mood), and they won't exercise which is critical to good health overall.

3. Stones are more likely formed from calcium oxalates. This can result from foods high in either calcium oxalates, or oxalates alone. As it turns out, most of our "preferred" tort foods are likely high in both. I can't prove it of course, but I imagine the majority of our food greens come from fields that are borderline calcium depleted. The grower is only going to add enough calcium to make the plants grow well, not be calcium rich. As these plants may be "expecting" higher calcium intakes than they are receiving, they may be producing excess oxalates.

so in a hopefully quick summary:
too much protein in a dehydrated tort = too much urea leading to gout (and other possible conditions not discussed here)
stones are formed from calcium oxalates, not urea. Calcium, oxalates, and calcium oxalates are all abundant in typical tort food. The balance varies with individual plants depending on many factors.

My remaining questions are:
Do the stones formed of calcium oxalates in torts only result from calcium and oxalates in the torts blood?

Does already combined calcium and oxalates in the diet contribute to these stones. (as I understand it calcium oxalates are not "digestable" and only irritate the digestive tract)

Does excess calcium in the diet lead to stones? (oxalates are a natural "ingredient" to all living things. Aside from other functions necessary to life, oxalates are there to deal with excess calcium. Too much calcium is detrimental, and plants form Calcium Oxalate Crystals to deal with it. These crystals build up in the plants as they have no way to flush them as animals do).

Could there be such a problem as oxalate defficiency (an animals own formed oxalates, not dietary) resulting from excess calcium?

Can gout be cured? Can the body clear those urea crystals over time?

 

[Torty Mom]

Balboa, that was awesome! So, did you ever get to see Daisy Lou's xray? Her entire digestive system is covered in stones. Nothing in the bladder, so are her stones calcium oxalate stones?

Danny and Balboa what do you think they are? I am so confused!

 

[egyptiandan]

Excellent explanation

Bladder stones is probably not a good description as they only get stuck there and added to there, but aren't started there. They are started in the intestinal track and usually get passed. They tend to be the hard gritty bits that can be in feces or uric acid. Some get caught in the bladder, if they are there for any length of time the body tends to want to add more to the stone because it's irrating the body. The stone than gets bigger and bigger. Some get passed before they get to big to come out and others don't (there are pictures somewhere on the forum of a baseball size stone that came from a Desert tortoise).

Danny

 

[Balboa]

I'm no vet, doctor or scientist, but I did go back and look over the old threads on Daisy to check out the x-rays. I can't say one thing or another looking at them, obviously Danny is much more qualified there. LOL

biology can be a funny thing, and tortoise biology is very different from our own. From what I've learned from Danny now, I'd have to say those are calcium oxalates. The "common" term may be urate stones, simply because in humans they form in the urine.

As I'm understanding it from Danny, in a tortoise, the bladder is open to the bowel, someone please do correct me if I'm wrong on this. That means though the bladder may be the initial source of stones, they pass easily into the bowel, where they may accumulate or continue to grow. It seems to me that it should be possible for dietary calcium oxalates to bind with already formed stones, making them even larger.

Its an easy thing to get hung up on, but I seriously believe most captive tortoise problems stem from inadequate hydration. If Daisy was kept too dry and not fed enough fiber, it would seem easy to develope blockages and large stones, even with "normal" and nearly ok husbandry practices. (I think what has been normal for a long time is inadequate, but that is my own theories).

Of course, like I said, I'm just a layman trying to wrap my head around this stuff too, and I may be understanding some key things wrongly.

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Well Danny was typing that excellent explantion while I was typing that last post. Thanks Danny! that answers more of the puzzle for me. So no, the "bladder stones" don't even start in the bladder.

 

[Torty Mom]

Thanks Danny and Balboa! You both rock!! LOVE YA!!!!

Seriously, I appreciate all the help I get and it's amazing how much I have learned and continue to learn.

So we will call them calcium oxalate stones. Daisy Lou has COS!!

Balboa, Daisy Lou had HORRIBLE, HORRIBLE care. But she is mine now and is on the road to being healthy!

 

[RianSeeking]

And I'm guessing maybe Josh is suffering from gouty arthritis.

 

[Annieski]

I just wanted to add 1 slight correction. The bladder--intestines--and reproductive organs are 3 separate systems. They do not open in to each other--but rather in to the cloaca. Think of the cloaca as a 3-way valve. All comes out 1 opening---but there are 3 separate origins, each with their own "valve".

 

[egyptiandan]

Actually the bladder does open into the intestine, with a very large opening (not like the little tube we have) in tortoises. I'll have to find a diagram when I get home.

Found one http://www.turtlestuff.com/turtleanatomy.html

Danny

 

[Balboa]

To further complicate things (at least to my head)
in humans urea does appear to form stones.
http://www.bing.com/health/article/mayo-125674/Kidney-stones?q=kidney+stones&qpvt=kidney+stones
though most are still primarily calcium and oxalates.
maybe it has to do with the more "closed" nature of the human urinary tract versus the chelonian?
Dang this is interesting stuff, and actually has a lot to teach us about how we take care of ourselves.

 

[Tracy Gould]

all this what's in different food confuses me i have learned to vary Shelbys diet which is easy to do in the spring and summer but harded in the winter, i have been relying on different mixes of lettuce to get him through the winter could this cause problem with him? I am starting to look for the weeds in the garden again and know to only feed Dandelions every so often as they are high in oxalates which is frustrating as they grow like mad in the garden and Shelby loves them lol. I do not think I will ever get my head around whats in the food i feed but hopefully i am doing things right.