Feline Inappropriate Elimination: Kidneys and Crystals and Stones, oh my!

Struvite crystals in urine - the most common type we see

Even if your cat is currently using the litterbox and not eliminating elsewhere, he or she may be visiting the litterbox less frequently than necessary, which can lead to urination issues down the road. We strongly recommend making your cat's litterbox situation as ideal as you can to help prevent urination issues.

Why is it a bad idea to urinate infrequently? If a cat holds his urine in his bladder for a long period of time, the urine becomes more concentrated. Concentrated urine has more “stuff” in it – more cells, more protein, more body by-products, etc. and the more stuff that is in the urine, the more likely it is to stick together and form crystals and stones. Urinary crystals and stones are uncomfortable and can lead to some of the medical reasons why cats avoid the litterbox.

This is one of the reasons that, even if we suspect a medical issue, we will discuss ways in which you can make your litterboxes more pleasant for your cats. Many of the elimination problems we see are complex and may have several contributing issues that need addressing. Treating the medical condition in conjunction with making changes to the litterbox will often speed your cat's recovery, and encourage them to return to the litterbox sooner.

**NOTE: many times, a cat will not 100% stop using the litterbox - they are fastidious about their environment and instinctively want to use the box. Most cats will use the box sometimes and eliminate elsewhere other times, so just because your cat is still going in the box sometimes doesn't mean that there isn't a medical problem. Also, just because your cat has always used the litterbox before doesn't mean that there isn't something about the box they don't like. Again, cats want to use the box, so are often very tolerant about litterbox situations that they consider to be sub-par - they just go less frequently, or they tolerate the box as-is until something else in their life changes.**

There are a number of medical reasons why a cat will stop using the litterbox:

Once removed from the bladder and dried, crystals look like sand.

--Urinary crystals or stones: Crystals and stones can be found in any part of the urinary system – the kidneys, the ureters, the bladder or the urethra. In male cats, these situations can quickly become an emergency, as clumps of crystals or small stones can become lodged in the tiny tube that leads from the bladder to the outside of the body (the urethra). This blocks the passage of urine, which means that the urine has nowhere to go, except to backup towards the kidneys. This causes the kidneys to start to shut down, since they can’t pump out any more urine. We call these cats “blocked cats”. Their bladders feel hard and firm, their bellies are tender, and the bladder can be in danger of breaking, like an over-inflated balloon. These kitties may be straining in the litterbox and not producing anything, or may just dribble a few drops of urine in the box. They are painful and may not eat, or may vomit near the litterbox. Again, this is an emergency, and a cat in this situation should be seen by a veterinarian as soon as possible!

Urinary crystals tend to show up well with an ultrasound but not on x-ray. Urinary stones will often show up questionably on ultrasound but will show up better on x-ray. There are a rare few stones that will not show up on x-ray, however (we call these "non-radiodense" or "non-radio-opaque" stones). Because of this, if the presence of a stone is suspected, it may be recommended or necessary to do both an x-ray and an ultrasound to confirm its presence. Because of the size of urinary stones, it is not likely that they can be diagnosed with just a urinalysis because they will not pass out of the bladder.

A urinary bladder full of stones.

Sometimes, a cat may show no real indication of bladder stones or bladder discomfort.  One of our technicians, Jennifer, has a cat named Marley whose only indication that he had stones in his bladder was that he stopped squatting in the litterbox.She was frustrated because he was standing in the box and urinating a good stream of normal-looking urine over the edge of the box. She thought that he was having problems with hip arthritis, but when the x-rays were taken, the hips looked normal and there were 9 stones visible in the bladder! A quick urinalysis indicated that there was microscopic blood in his urine but no crystals or infection. Shortly after that, he had surgery to remove the stones from his bladder (a cystotomy) and after he recovered from surgery, he started squatting to urinate again. He must have felt so much better!

For females, the situation is less dire, but the symptoms are similar – straining in the box, you may see bloody urine, dribbling, crying in the litterbox, or inappropriate elimination.

Dr. Bailey's cat, Tic Tic, has kidney stones in both kidneys.

If the stone is in the kidney, it is less treatable. In some cases, the stone may pass out of the kidney and become stuck in the tube that goes from the kidney to the bladder (the ureter). In this case, the kidney may stop working. In other cases, the stones are so big they will not pass, but surgical removal involves the risk of damaging the kidney's delicate filtration structures. In some situations, a change in diet can help dissolve the stones, or if the stones are limited to one kidney, the kidney can be removed.

These problems are one of the reasons that we recommend that cats eat 6-9 oz canned food daily. Canned food helps dilute the urine and helps prevent the formation of crystals and stones.

This x-ray is of a cat that is severely constipated.

--Constipation: Cats that cannot pass stool are uncomfortable, and may strain unproductively in the litterbox, only to defecate elsewhere later. They also may vomit near the litterbox. They may pass small amounts of diarrhea around a solid stool that they cannot pass. Some of these symptoms may be easily confused with straining to urinate, or a blocked cat, so don't feel bad if you call for an appointment for straining to urinate and discover your cat is constipated, and don't assume that your straining cat is constipated only to find out later when your cat is very ill that he was blocked.

Cats with a history of urinary crystals or stones should have a urine sample and/or x-rays checked every 6-12 months for the rest of their lives in order to prevent recurrence. They should also eat canned food only to help keep their urine dilute and the pH more neutral to help prevent recurrence. If your cat absolutely will not eat canned food and has a history of urinary crystals or stones, a prescription-grade dry diet may be necessary.

For these reasons, it is good to occasionally monitor your cat's behavior in the litterbox and become familiar with what is normal for your cat, so that if something changes and you become concerned, you can describe it accurately to the veterinarian.

--Diabetes: Cats with undiagnosed or uncontrolled diabetes drink large amounts of water and also urinate large volumes. These cats may not be able to get to the litterbox in time to urinate, or they may object to a flooded litterbox that has not yet been scooped. They may also just not feel well and choose to urinate elsewhere because they feel poorly. Cats with diabetes also tend to eat well but lose weight. Long-term, uncontrolled diabetes can lead to a life-threatening situation called Diabetic Ketoacidosis (DKA), which usually requires hospitalization and intensive care.

--Hyperthyroid disease: Cats with overactive thyroid glands also drink a lot and urinate a lot. These cats have an overactive metabolism – high heart rate, increased hunger, weight loss, and often high blood pressure. Just like diabetics, they may not be able to get to the litterbox in time to urinate, may flood the box and then not want to use it again, or may just feel poorly and choose to urinate elsewhere as a result. Sometimes, these cats also have soft stools, and may defecate outside the litterbox. They also tend to have high energy levels and may “talk” a lot, especially at night (we call this "inappropriate vocalization"!).

--Kidney Disease: Cats can lose up to 75% of their kidney function before they start to show signs of illness. Like diabetics and hyperthyroid cats, these cats will usually drink more and urinate more, but they are more likely to feel poorly and eat less. Because their kidneys are not filtering the toxins from their bodies normally, the waste products of normal life tend to build up in the blood stream and cause them to feel nauseous and lackluster. Just like diabetics, they may not be able to get to the litterbox in time to urinate, may flood the box and then not want to use it again, or may just feel poorly and choose not to urinate in the box.

Bacterial culture is a very good way to help I.D. bacteria in the urine.

--Urinary tract infection: Occasionally, cats will develop a bacterial infection in their bladders. This could be due to poor grooming around the rear end, often due to weight issues. Some cats are naturally susceptible to urinary tract infections, or may become more susceptible due to a medical issue, such as diabetes. Normal urine is sterile while in the bladder. It isn't until the urine passes out of the body that it picks up bacteria. Because of this, the best way to collect the sterile urine is with a needle inserted into the bladder. Any urine that passes through the urethra will have bacterial contaminant from the external genitalia and fur.

Sterile urine collected directly from the bladder will not grow bacteria on a culture plate. Urine that has an infection will grow in little dots and lines called "colonies" - usually in less than 24 hours. These colonies can then be easily classified by looking at them under the microscope and noting their patterns of growth, as well as the color and smell of the colonies. Some antibiotics work better for some types of bacteria than others, and the doctors can make better decisions about which medication will best treat the infection. In some recurrent cases where the cat is hard to medicate or has not been fully treated in the past, the culture plate may need to be sent in to a reference laboratory for more specific testing (called a "culture and sensitivity") that includes testing for antibiotic sensitivity or resistance.

It is also because of antibiotic resistance that antibiotics should be given regularly for the entire course of the prescription, and not stopped when the symptoms of the infection go away. A few individual bacteria that linger can become a whole new infection that is stronger and more resistant. Some cats that have chronic recurrent urinary tract infections may really have one infection that never gets fully treated because the course of antibiotics is not long enough, the antibiotics are stopped too soon, or a urine culture is never rechecked after treatment to show that the infection has fully resolved.

In the case of a bacterial infection, white blood cells to fill the bladder to combat the bacteria, inflammation of the lining of the bladder may lead to blood in the urine, and there is also usually a change to the pH level of the urine (changes the acidity). These changes can make it quite painful to urinate, and the cat, not knowing that it is sick, may link the litterbox to the pain and decide to go elsewhere, in search of a comforting surface to urinate on.

Because of these issues, it is important to check a urine sample, bloodwork, and/or x-rays when a cat is urinating or defecating outside the box in addition to making changes in litterbox husbandry.

More information about inappropriate elimination:
Lovin' the Litterbox: Husbandry Reasons Why Your Cat May Not Use the Litterbox
Acting Out All Over the House: Behavioral Reasons Why Your Cat May Not Use the Litterbox
Breaking the Cycle of Smell: How to Stop Habitual Elimination Problems