The name keeps changing, but the disease remains the same. Called Feline Lower Urinary Tract Disease (FLUTD), Feline Urologic Syndrome (FUS), or Idiopathic Cystitis, usually veterinarians are referring to a set of symptoms that include bloody urine, straining, bladder discomfort (leading to crying and frequent attempts to urinate), and urinating around the house. However, to look into these symptoms, we actually have to back away from lumping it into a single disease, and look at the individual cat (case).
One important point, is that referring to these cases as "bladder infections", is usually a mistake. Bacterial infections are usually not causing the problem. Bacterial infections are present in less than 3% of FLUTD cases. Antibiotics that are frequently prescribed, usually are not helpful.
So why are antibiotics usually prescribed? Firstly, most cases are idiopathic cystitis (discussed later) and will get better on their own in 3-to-7 days regardless of treatment, so prescribing any medications will seem to make it better in that time span. (If it gets better in 3 days, the vet is the hero. If it takes 7, the second vet who saw it after 3 days and prescribed the "better" medication will be the hero.) I guess it also gives the owner (and the veterinarian) the perception that they're actually doing something to help. Secondly, at least the antibiotics may be helping the 3% of cases that are infections.
As mentioned earlier, each case must be handled individually. Some cats will have infections. Culturing the urine will help identify those with bacterial infections, and allow for the appropriate antibiotic for treatment. Some cats will have bladder stones, and some will have bladder tumors or cancer. Radiographs and ultrasounds are needed to identify these cases.
In the cats with no stones, no tumors, no cancer, and no infections, most of these cases are "idiopathic", meaning a cause will not be identified. This comprises the bulk of FLUTD cases in cats. These are the cases that get better in 3-to-7 days, regardless of treatment. It's possible that viral infections, possibly even chronic viral infections, may play a role in these, but at this time, it has not been proven. Stressful events, such as a move, new people or animals in the house, discord within the household, may precipitate a bout of cystitis. A notable change in the weather can often be associated with cystitis cases. It's not unusual as a veterinarian not to see a case of this for months, and then, after a sudden autumn cold spell, suddenly have several cases in one day. The cats that develop these problems, may also have a genetic or hormonal predisposition to developing cystitis, or in responding to stress abnormally.
In cases of idiopathic cystitis, most cats will get better on their own. As veterinarians, reducing discomfort may be one of the most important things we can do. For this, a variety of antispasmodic, nonsteroid or steroid antiinflammatories, and other drugs are often prescribed.
We also cannot forget that some cats have continuing problems, or frequent recurrences, and we cannot forget that cystitis in male cats can have life-threatening consequences, regardless of the cause.
Male cats present a different problem than female cats. Male cats are in danger of obstructing, in other words, developing a urinary blockage. In female cats, that's very rare. The difference is due to the differences in the male and female anatomy. A urinary obstruction is a life-threatening emergency, that must be addressed immediately.
What about diet? Diet changes have been a mainstay of treatment for a long time, although the thought of how to alter the diet, and why the alteration is helpful, have changed. People used to talk about the "ash content" of the diet, and people started checking the food labels for "ash". This turned out to be too simplistic. As food companies reduced ash content, it just made things worse. The ash content is the inorganic residue that remains when the diet is incinerated, and basically refers to the mineral content. We now know that the relative magnesium, phosphorus, and calcium contents are more important than the total ash content. And, we also now know that the ability of the diet to alter the urinary pH and the urinary moisture content (or specific gravity) is particularly important.
We also now know that diet does not alter the occurrence of cystitis, and is most important in preventing obstructions. So, diet is most important for male cats that have shown a predisposition for developing cystitis. When a cat develops cystitis, the bladder wall becomes inflamed, produces excessive mucous, and bleeds into the urine. If the urine pH is high, magnesium, a key ingredient in struvite crystals (the most common problem-causing crystal type), tends to precipitate into the urine. If the magnesium content of the food is high, more mineral precipitate will form. If the urine specific gravity is high, which relates to how much fluid the kidneys are producing, again more crystals or precipitate will form. This mineral precipitate mixes with the blood and mucous to form solid plugs, that obstruct the bladder in male cats.
There are a few more points to mention. First, the concentration of crystals in the urine is a reflection of the diet, the urinary pH, and the specific gravity of the urine. Crystals will form in the presence or absence of cystitis, and is not an indication of cystitis. Second, if bladder stones are present, their type may not relate to the type of crystals found on urinalysis, and , in fact, stones can be present in the absence of crystals. Third, in predisposed cats, the occurrence of calcium oxalate stones or crystals may increase as we lower urinary pH and magnesium content in an attempt to reduce struvite formation.
Some cats, particularly older cats, will chronically have blood in the urine, and a cause cannot be identified. Often the specific gravity of the urine in these cases is high. Encouraging fluid intake, in an attempt to keep the urine more dilute, may help with some of these cats. A water fountain, lactose-free cat milk, chicken broth, tuna water, and adding water to canned food may encourage fluid intake.
The cat's blood pressure should be checked. Hypertension could result in blood in the urine. Primary hypertension is not recognized in cats, and if hypertension is present, there should be another disorder causing it.
The source of blood in the urine could be the kidneys, even if bloodwork and urine specific gravity do not indicate kidney failure. So kidney function and morphology/pathology should be checked and monitored if problems are on-going.
Lastly, clotting disorders can be a totally unrelated cause for blood in the urine.
