First of all, some definitions:
FLUTD: Feline lower urinary tract disease.
This catch-all term basically covers ALL types of diseases and disorders affecting the feline lower urinary tract
(i.e. the bladder and urethra).
Contrary to popular perception, the majority of FLUTD is *idiopathic*, which basically means "Hell if we know what's going on." The bladder/urethra is inflamed, the cat is in discomfort and other symptoms may be present,
e.g. hematuria (bloody urine) or dysuria (difficulty urinating) but no underlying cause can be found.
Of those cats who have FLUTD, about 15-20% will have urinary crystals,
about 5%-10% will have some kind of anatomic deformity (an unusually narrow urethra, for example),
about 1% will have an actual infection,
and about 1% will have something really, really nasty like cancer.
FLUTD affects about 1% of the total domestic feline population, though in my opinion this number may be low because the primary symptom of FLUTD is inappropriate peeing, which most people assume is behavioral and treat it as such instead of having a pee sample analyzed.
Cystitis: the dictionary definition for this is "inflammation of the urinary bladder," and this term is often used synonymously with FLUTD.
FUS: Feline urological syndrome. Initially defined as "the feline disease syndrome characterized by dysuria, urethral obstruction, urolithiasis [see below] and hematuria", researchers quickly found that most cases of lower urinary tract disorders in cats didn't involve urolithiasis, and this term was eventually abandoned in favor of the more general FLUTD.
UTI: Urinary tract infection. Most people use this term to describe FLUTD,
but actual urinary tract infections are very rare in cats (if you do the math, if about 1% of all FLUTD cases are actual infections and FLUTD affects only 1% of all cats, only 1 in 10,000 cats will experience an actual UTI). Most cases of FLUTD are sterile.
The hances of a cat having a UTI are slightly elevated if it has urinary crystals because the accompanying abrasion/inflammation makes it easier for infection to set in.
For this reason, many vets like to prescribe antibiotics "just in case" infection develops, but I talked to a vet about just this issue and he said that according to the studies he's encountered, prophylactic antibiotic usage is rarely useful for cats with urinary crystals. The sterile nature of FLUTD, even when struvite crystals are present, is in direct contrast to what causes urinary tract problems in dogs, which are frequently caused by bacterial infections.
Dysuria: Painful urination
Wherein the cat painfully makes little dots of pee in the litterbox, either because of muscle contractions or because the urethra has been partially blocked by uroliths
Hematuria: Bloody urine
Pollakiuria (sometimes used synonymously with Polyuria): Urinating with abnormally high frequency
Urolith: Essentially, calculus (a compound consisting of minerals and organic material) found in the urinary tract
(Feline) Urolithiasis: Fancy term for "peeing crystals"
Struvite crystals: A type of of urolith consisting of magnesium, ammonium and phosphate crystals.
Often known as MAP uroliths by fancy-dancy vet types. Struvite crystals form in alkaline urine, and are generally very responsive to dietary therapy, i.e. if you make a cat's urine pH more acidic than 6.5, the crystals [assuming they're not too big, as a crystal's solubility depends on its size] will generally dissolve. They were once by far the most common type of urolith found in cats, but they're now just about as common as....
Calcium oxalate crystals: a type of urolith consisting of , uh, calcium oxalate,
also commonly abbreviated as CaOx. CaOx forms in acidic urine, unlike struvite crystals, and are not particularly responsive to dietary therapy. If you have a cat with CaOx problems, surgery is the only way to remove the uroliths. CaOx hits older cats (which makes sense, since older cats are more prone to metabolic acidosis, which in turn strips calcium from their bones, thus making the saturation of calcium salts in the pee more likely). Genetics can also predispose a cat to CaOx formation, because Persians and their outcrosses (like Himalayans) are more likely to suffer from these crystals than the general population of kitty cats.
short answer: nobody really knows for sure, though several different risk factors have been identified.
Long (REALLY long) answer:
For a long time, researchers concentrated on eliminating struvite urolithiasis, and based on their results, they suspected excess magnesium in cat food and food that predisposed cats to form alkaline urine (more on what makes urine acid or alkaline later) were the primary culprits.
And sure enough, reducing the amount of magnesium in the food and adding urinary acidifiers helped manage the problem. Unexpectedly, though, the number of cats with calcium oxalate uroliths started increasing, until they're now as common (if not slightly more common) as struvite. This makes sense for various reasons:
- Magnesium inhibits the formation of CaOx uroliths. Cutting down on the amount of magnesium in the food meant there were fewer CaOx inihibitors.
- CaOx forms in acidic urine.
- Most cats with urolith problems eat significant amounts of dry food. Because cats evolved as desert animals and are used to deriving much of their water from their food (which is typically 60-75% moisture), their thirst instinct is pretty shitty.
As a consequence, cats eating only dry food will receive only 50% of the total water compared to cats eating only canned food (assuming both types of food contain the same number of calories).
Drinking insufficient water means that the urine tends to be more concentrated.
And if you remember your high school science classes, less water means it takes much less solute to achieve the saturation point and form precipitate.
(If you remember the rest of your science class, you'll remember that heat, agitation and pH can also affect solubility and therefore saturation.)
In plain terms: more concentrated pee = higher likelihood of urolith saturation = higher likelihood of urolith precipitation and formation.
This simple fact has led to increased water intake being a cornerstone therapy for urolithiasis for just about every species out there, including people.
Unfortunately, "prescription" diets for cats with urinary crystals are available in dry form, and vets often don't discuss the importance of switching a cat with urolith problems to a diet high in moisture, they just hand over the bag of s/d or c/d kibble and say "Here ya go, feed this to the cat for the rest of its life." But then the restricted magnesium content, the acidifying ingredients and concentrated pee now means it's easier for cats to form CaOx stones.
And then other researchers pointed out: hey, most cases (about 70%) of FLUTD don't even have any kind of apparent cause. WTF? What are the predisposing factors for those cases?
Interestingly enough, just as in cases of urolithiasis, the major risk factor seems to be dry food. One study found that cats with idiopathic FLUTD were about three times more likely to consume only dry food compared with the general cat population. Another study found that cats with idiopathic FLUTD treated with prescription acidifying formulas responded well, but the recurrence rate for those on dry food was about 3 times that of those on canned food. Researchers aren't quite sure why, but they speculate it has something to do with solute load.
In summary: Water. It's good for your cat's pee hole.
Another question people often ask is: what foods and food supplements effectively acidify a cat's urine?
This question involves a really tricky subject, i.e. the acid/base balance of a living organism's body.
This is a pretty complicated subject and I only understand the very basics of what's involved, so understand that you're only going to get the most basic of the basics.
The acid/base balance can be affected by many things, but the two biggies essentially involve breathing and food intake.
Breathing produces alkaline by-products, which may very well be why some cats who are prone to uroliths have "attacks" when they're stressed out (stress = hyperventilation = alkaline by-products in body = alkaline urine).
And foods can have either have an acidifying or alkalinizing effect on the body (and therefore the urine).
First of all, it's important to distinguish between the pH of the food itself, and the effect the food will have on the body's pH after it's been digested.
You *cannot* predict the effect a certain food will have on the body's pH based solely on the food's actual pH.
Feeling a bit confused?
I like to use lemons as an example. Lemons are intensely acidic, and most of us know this.
But eating lemons or drinking lemon juice will not result in a more acidic urine pH--on the contrary, lemons have a strongly alkalizing effect on the body when ingested.
Why? Because lemons (and just about every fruit and vegetable you can think of) are a significant source of dietary bicarbonates, which have an alkalizing effect.
With vinegar, it's the same thing: vinegar is essentially acetic acid, but when ingested, it alkalizes the body because it produces alkaline by-products after the body breaks it down.
Now meat, on the other hand, produces various acidic by-products (mostly phosphate and sulfate anions) when digested, so they have a net acidifying effect on the body. But if you check the pH of meat itself, it's pretty close to neutral--it's certainly nowhere close to being as acidic as a lemon, or vinegar.
Now on to three very popular "natural" supplements that are touted as urinary acidifiers:
cranberries, blueberries and dl-methionine (an amino acid).
Out of these three, only one actually acidifies urine.
And if you remember my comment about how fruits and vegetables almost always have a net alkalizing effect, you'll probably have guessed that dl-methionine is an actual urine acidifier and while cranberries and blueberries more likely than not will actually alkalize the urine.
And frankly, the popularity of cranberries and blueberries as urinary tract supplements stems from their use to treat *human* urinary tract disorders--specifically, urinary tract infections.
Cranberries and blueberries basically contain a compound that interferes with the bacteria's ability to adhere themselves to the bladder walls.
And once again, feline UTIs are extremely rare, so giving Kitteh a shitload of of cranberries to help treat struvite crystals will not only be futile since there's a very good chance that the FLUTD is sterile, but it'll very likely be counter-productive because if anything it'll make the urine more alkaline.
Dl-methionine, on the other hand, actually DOES acidify the urine because it's a sulfur-containing amino acid,
which then breaks down to sulfate groups that acidify the urine.
You can get it in any decent grocery store at the vitamin aisle, where all the other amino acids (like taurine or lysine) are stocked.
Vets dispense a type of gel called Methigel that's basically dl-methionine in gel form.
Giving an adult cat up to 1500 mg dl-methionine a day is probably safe (depending on the size of the cat),
BUT be careful with this shit and consult with the vet before starting methionine therapy because an overdose can cause Heinz body anemia (the same kind of anemia caused by onions).
Researchers found that doses of 1000 mg/kg bodyweight/day (which amounts to about 4500 mg per day for a 4.5 kg cat, which is equivalent to about 10 lbs.) caused severe Heinz body anemia,
while 500 mg/kg bodyweight/day caused moderate anemia that corrected itself after a month, indicating that the cats probably adjusted to those levels of dl-methionine in their diet.
Is acidifying the urine using dietary supplements an appropriate therapy for every cat?
Cats with kidney disease are pretty prone to metabolic acidosis, so acidifying their systems even further is a really shitty idea.
Older cats are also more prone to metabolic acidosis, so feeding them foods containing urine acidifiers should be approached with extreme caution and with vet supervision.
The best approach to treating cats with chronic FLUTD problems who are otherwise young-ish and healthy
is to ensure that the water intake is adequate (i.e. feed foods high in moisture),
feed foods that are high in meat proteins (meat being a pretty efficient urine acidifier with none of the drawbacks of dl-methionine therapy),
minimize the amount of carbohydrates in the diet (new research coming out shows that starches seem to encourage struvite crystal formation),
make sure the diet is balanced if you're feeding home-made food,
and feed as many small meals at regularly-spaced intervals as you can manage.
Minimizing stress (remember, stress as perceived by the cat can be very different from stress as perceived by us) for those cats who have crystal attacks after a freak-out is also very important.
Resort to dl-methionine only when these other approaches fail, and only with veterinary supervision.
Another myth that's been propagated in holistic health circles that I want to address
is the myth of the post-prandial alkaline tide. Holistic pet health heroes like Richard Pitcairn, Anitra Frazier and Kymythy Schulze have advocated feeding infrequent but large meals to cats, with enforced fasts in between.
Schulze's reasons for advocating this are different from Pitcairn and Frazier's, which seem to be partly based on the fact that a cat's urine pH rises after a meal.
This is known as the post-prandial alkaline tide.
What the two of them completely missed were these four simple facts:
- The alkaline tide happens 3-6 hours after a meal, not directly after eating food.
- The bigger the meal, the bigger the alkaline tide.
- Cats who eat several small meals a day have a more acidic pH on the average than cats fed only one or two big meals.
- Small felids eat up to 20 small meals a day in the wild. Given how big the average mousie, cricket or small songbird is, this makes sense.
The above information was culled mostly from Small Animal Clinical Nutrition, 4th ed.
The textbook actually has a handy-dandy little chart showing the little peaks and valleys of cats who eat several small meals vs. the gigantic spike for those who eat only a few big ones (the ones who eat small meals peak at about pH 6.5, while those who eat big meals peak at about 7.0).
Pitcairn and Frazier do a lot of fearmongering regarding this dreaded alkaline tide.
According to them, the cat only needs to SMELL the food and the poor dear's urine pH will spike through the roof.
This claim makes no sense whatsoever, because one can only imagine that a wildcat living in its natural environment and surrounded by small, scurrying critters that are all potential meals-on-wheels (so to speak) would have perpetually alkaline urine pH, when it couldn't be further from the truth.
Cats who hunt and eat a "natural" diet, i.e. several meals consisting of small, whole prey, tend to have urine pH ranging from about 5.9 to 6.4.
Now I'm not saying "you must feed your cats 10 to 20 meals a day!" if you happen to feed home-made food or canned food.
Most cats do fine on two meals a day. I feed mine two meals a day, three if I'm feeling sassy.
Ideally, though, if you could, feed them as many small meals as you can manage on your schedule,
and if your cat has FLUTD, doing this is even more important to avoid the large alkaline spike 3-6 hours after the meal.
You can use one of those timed feeders with ice-packs on the bottom meant to dispense canned food; they'll work equally well for canned food and for home-made.
Here are the studies I referred to while writing the above posts. Feel free to read them for yourself so you can determine if I'm full of shit or not. Pity I can't use HTML in this post, because I could've linked to these studies as I wrote about them and it didn't occur to me to use numbers to annotate the references, DOH!
Feline Reference Values for Urine Composition: www.nutrition.org/cgi/conte...32/6/1754S
Clinical evaluation of cats with nonobstructive urinary tract diseases: www.ncbi.nlm.nih.gov/entrez/query.fcgi
Clinical evaluation of commercially available urinary acidification diets in the management of idiopathic cystitis in cats: www.ncbi.nlm.nih.gov/entrez/query.fcgi
Evaluation of effects of dietary carbohydrate on formation of struvite crystals in urine and macromineral balance in clinically normal cats: www.ncbi.nlm.nih.gov/entrez/query.fcgi
Methionine toxicosis in cats: www.ncbi.nlm.nih.gov/entrez/query.fcgi
The Effect of Diet on Lower Urinary Tract Diseases in Cats: www.nutrition.org/cgi/conte...8/12/2753S
Association between patient-related factors and risk of calcium oxalate and magnesium ammonium phosphate urolithiasis in cats: www.ncbi.nlm.nih.gov/entrez/query.fcgi
Feline urethral plugs and bladder uroliths: A review of 5484 submissions 1998–2003: www.pubmedcentral.nih.gov/artic...r.fcgi
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