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Diagnosing Cat Litter Box Issues
A Focus on Disease and the Aging Feline

by Cynthia Jones
Fall 2004


House soiling or elimination outside of the litter box is the most common reason cats are turned in to shelters by their caregivers (Salman, Hutchinson, Ruch-Gallie et al., 2000).  Older cat caregivers sometimes choose to euthanize the cat when cleaning a soiled house becomes too taxing and there seems to be no solution to the problem.  Appropriate diagnosis and treatment of house soiling problems is of great importance for this reason.

Understanding what constitutes natural feline elimination behaviors is also vital.  This paper examines recent data from veterinary medical journals and publications in the hopes of offering caregivers who have older cats a better understanding of their litter box issues and treatment options.  Differentiating between behavioral and medical causes of house soiling is discussed as well as two success cases involving small populations of older, arthritic cats that will hopefully offer frustrated caregivers a good alternative to relinquishing their cat to a shelter or euthanasia.

Natural Feline Elimination Behaviors

First we must understand that behaviors we humans may find repulsive appear to be normal communication between cats.  Cats use scent marking via urine and anal secretions to communicate with one another (Neilson, 2000).  Spaying or neutering cats greatly reduces and usually even eliminates these marking behaviors.  Research has revealed that ninety percent of intact males significantly decreased marking after castration and that female cats in estrus (in heat and therefore not spayed) show an increase in marking (Neilson, 2003).  Regardless of the cat's spay/neuter status, natural elimination behaviors include investigating a potential spot, digging a hole, squatting to pass urine or feces, and covering the area of elimination.

The cat's choice of where to eliminate is only a problem if we perceive it to be.  In fact, some studies have shown a significant association between caregivers' perceptions of treatment outcome and the percentage reduction in frequency of inappropriate elimination (Marder and Engel, 2002).  Elimination behaviors perceived as problematic by some caregivers might not be perceived as problematic by others.  Despite what the children may think, an uncovered sandbox or garden looks like an ideal giant litter box to a cat and it's perfectly normal for a cat to urinate or defecate in such areas.

Identifying norms is key and it's obvious that the majority of cats have a natural inclination to eliminate in a clean, safe area where they can observe a spot, squat, and cover their waste.  There are many factors that can deter a cat from this "norm" of litter box use that must be ruled out before determining that the problem is medical or behavioral.

What to Rule Out Before Consulting A Veterinarian

Getting rid of the problem and not the cat is the goal.  Sometimes it's human behavior that needs changing.  It shouldn't come as a surprise that cats might have problems with a dirty litter box, too few litter boxes or litter boxes placed in a stressful location.  Any combination of these may be contributing to the house soiling problem (Marder and Engel, 2002).

Experiment with different types of litter (crystal versus clay for example), litter box designs (enclosed versus open or puppy pads versus walled box), and try placing the litter box in different easily accessible locations while paying attention to which box is used the most frequently if you keep more than one litter box available.  It is a good idea to have more than one litter box especially if there are multiple cats in the household.

Most importantly, keep the litter box clean by scooping several times daily and replacing the old litter with new at least once a week.  Whether we think like our cats or not, some cats might consider a litter box dirty if it has been soiled only once.  If multiple cats live in the household, consider setting up a video camera to monitor the litter boxes and what goes on in that general area (visit www.litterboxcam.com for a preview).  This is useful to see if a particular cat is intimidating or cornering another cat in the litter box frightening him or her from the area.  A cat may be avoiding the litter box due to anxiety from being attacked or cornered (Neilson, 2004).  If the house soiling problem persists, you can probably rule out cleanliness, location, and most stress related factors.

The Medical Versus Behavioral Debate

A necessary initial step in addressing the house soiling issue is attempting to discern if the problem is medical or behavioral.  This can be complicated work as the two are usually not mutually exclusive.  House soiling may initially be the result of a medical problem and even after that problem is resolved, the house soiling may continue for behavioral reasons (Neilson, 2003).  For instance, the discomfort associated with a medical problem leads to the litter box becoming aversive and the cat's choosing an inappropriate place to eliminate.  The use of this new location becomes habitual and reinforcing and therefore the behavior is maintained (Marder and Engel, 2002).

Identifying the Culprit

In multiple cat households, the first step involves determining which cat or cats are the culprits.  Veterinary expert Jacqui Neilson, DVM, whose writings and observations appear to dominate this area of study, offers some advice in her article "Thinking Outside the Box: Feline Elimination." She suggests three methods for identifying the correct cat.  Which one to use depends on whether the problem is urination or defecation outside of the litter box.

Confinement is the first (self-expanatory) option that works for both urination and defecation problems but doesn't always produce immediate results.  The flourescein dye test is an option for determining which cat is urinating outside of the litter box.  The dye strips can be administered orally within a gel capsule.  Twenty-four hours after administration the cat will eliminate bright yellow-green fluorescent urine when viewed under a black light.  Neilson notes that untreated urine will also fluoresce so the caregiver must become familiar with the difference between normal and enhanced fluorescence.

If inappropriate defecation is the problem, she suggests using non-toxic green crayon shavings mixed with Cat X's food while Cat Y gets the non-toxic purple shavings.  The color that shows up on the living room rug will identify the culprit.  Better yet, if you have access to a video recorder or camcorder, simply set it up to record the area that is being soiled and catch the culprit on camera.  Once the caregiver has identified the problem cat(s), and ruled out factors such as a dirty litter box or too few litter boxes, the cat should be taken to a veterinarian for a thorough history and medical evaluation.


A systematic (versus random treatment application) approach to managing cats with elimination issues should help veterinarians achieve treatment success (Neilson, 2003).  This systematic approach begins with proper diagnosis.  There are three differential diagnoses for urination or defecation outside of the litter box and they are: Disease, marking, and inappropriate elimination (Marder and Engel, 2002).  This paper discusses the disease diagnosis as it is more prevalent in older cats.

Discomfort associated with medical problems is often the initiating factor for an older cat with house soiling issues.  The list of diseases that cause polyuria and other elimination problems is endless, but frequently mentioned in the research literature are: arthritis, diabetes mellitus, urinary tract problems such as stones or cystitis, hyperthyroidism, drugs such as steroids or diuretics, infections such as feline leukemia virus (FeLV) or feline immunodeficiency virus (FIV), seizures, and any pathology of the bladder, gastrointestinal tract, endocrine system, and musculo-skeletal system (Neilson, 2004) (www.vetmedcenter.com, 2000).

Diseases that cause polyuria lead to urination outside of the litter box due to the frequency or urgency associated with elimination (Neilson, 2000).  Arthritis and degenerative joint disease in particular can lead to house soiling issues.  Degenerative joint disease (DJD) has been found at incidences as high as ninety percent in cats older than twelve (Hardie, Roe, and Martin, 2002).  Due to the design of most litter boxes, an arthritic or DJD geriatric cat is going to have a difficult time stepping in and out of a typical litter box.  If the litter box is located upstairs, in a basement, or an area the cat has to jump to reach, the cat is going to have a difficult time traveling to or accessing the box and may choose an alternative location to eliminate.

Veterinarian and feline house soiling expert Jacqui Neilson (2004) recommends several diagnostic tests as part of a comprehensive physical examination.  But first a complete history is essential for proper diagnosis and treatment.  Make sure your veterinarian knows the frequency and pattern of elimination, diet history, etc.  in addition to your cat's complete medical history.  As the caregiver you are largely responsible for providing the veterinarian with detailed and accurate descriptions of your cat's behaviors and history.  Your veterinarian should also be asking you questions about how often you scoop, wash, and replace the litter in the litter box with fresh new litter.

If the cat is urinating inappropriately, the diagnostic work-up should include the following:

If the cat is defecating inappropriately, the diagnostic work-up should include the following:

Appropriate medical treatment of the diagnosed medical condition may solve the house soiling problem.  However, there is a risk that even with the medical condition resolved the cat has developed a habit or aversion to the litter box that still needs to be addressed with behavioral treatment.  We can make changes in the cat's environment that work with the medical diagnosis.  The following section describes one such treatment plan.

A Successful Behavioral Treatment

Even though the initiating factors of a house soiling problem may start out as medical, the next step in treatment after the medical issues have been addressed is behavior focused.  This usually means making the litter box situation as pleasant as possible by tailoring the litter box to the individual needs of the cat. (Marder and Engel, 2002).  For the past four years, the Zimmer Foundation has housed and hospiced two groups of 'retired' elderly cats at separate cage-free facilities in the area of Ann Arbor, Michigan.  The majority of cats in this geriatric group have medical problems ranging from arthritis to hyperthyroidism.

Staff at the foundation's life care centers were asked to log each event of elimination outside of the litter box on a computer database detailing the type of event (urination or defecation), location, and identification of the cat if known.  At one point it was not uncommon for house soiling events to occur on a daily basis usually in the same two or three different areas at each facility.  Zimmer Foundation Vice-President Kitty Zimmer experimented with every type of cat litter on the market and different types of litter boxes.  The boxes were scooped several times daily and were also cleaned and replaced with fresh litter at least once a week.  Litter boxes were placed in all corners of the house and were easily accessible, yet the problem of house soiling continued.

After much trial and error and sampling everything available for cats that the market had to offer, she discovered a product intended for dogs.  These "puppy pads" are much like a diaper that is placed over a flat rectangular tray.  These puppy versions of a litter box were placed in the corners of the living areas that were regularly being soiled.  They were an instant hit with the cats and have stood the test of time.  For the entire year the puppy pads have been in use the frequency of house soiling has been reduced by almost one hundred percent at both life care facilities.

Why are the puppy pads a success for this particular population of cats?  First of all they are flat and rise only about an inch off the ground, allowing arthritic or DJD cats to easily step into and out of them versus having to climb over the edge of a typical high-sided litter box.  Because the puppy pads are litter free, aversions to a particular type of litter are not an issue.  The trays are easily accessible and the disposable "diapers" can be replaced as frequently as needed allowing for a high level of cleanliness.

To implement such a "treatment" plan in one's own home usually requires some compromise.  Some caregivers may not be willing to use the puppy pads for aesthetic reasons and prefer scooping litter rather than changing a diaper on a daily basis.  Because the puppy pads are not covered with a lid to keep waste out of sight, some caregivers may find them undesirable.  Once again the success of such treatments greatly depends on the cat caregiver's willingness to change his or her own behavior to accommodate the needs of an aging feline.


When an older cat develops a house soiling problem, the cause is often initially medical rather than behavioral.  When an elimination problem continues after a medical problem has been remedied or ruled out, a behavioral diagnosis should be sought (Neilson, 2004).  Cats are very sensitive to the cleanliness of their environment and instinctively choose certain areas to eliminate.  Once the cat doing the house soiling is identified and factors such as cleanliness, location, and intimidation by other cats are ruled out, a visit to the veterinarian is recommended for a thorough history and physical evaluation.

This paper lists many of the diagnostic tests appropriate to the type of house soiling problem.  Once a medical diagnosis has been issued and treated, caregivers often still need to make changes in the cat's environment to accommodate the cat.  Much as a person in a wheelchair requires a ramp or other specified surface to easily access an area, an older cat often needs the same consideration concerning litter box design and placement in the home.  The Zimmer Foundation's two groups of geriatric cats offer an example of successful implementation of a behavioral program that accommodates the needs of older, arthritic and otherwise medically challenged felines.


Hardie, E.M., Roe, S.C., and Martin, F.R.  (2002).  Radiographic Evidence of Degenerative Joint Disease in Geriatric Cats: 100 cases (1994-1997).  JAVMA.  220: 628-32

Marder, Amy and Engel, Joan.  (2002).  Long-Term Outcome After Treatment of Feline Inapporpriate Elimination.  Journal of Applied Animal Welfare Science.  5(4): 299-308.

Neilson, Jacqui.  (2003).  Feline House Soiling: Elimination and Marking Behaviors.  The Veterinary Clinics Small Animal Practice.  33:287-301.

Neilson, Jacqui.  (2000).  Friskies Behavior Companion:  A Clinical Reference Guide for Veterinarians.  Friskies PetCare Company.

Neilson, Jacqui.  (2004).  Thinking Outside the box: Feline Elimination.  Journal of Feline Medicine and Surgery.  6:5-11.

Salman, M.D, Hutchinson, J., Ruch-Gallie, R., et al.  (2000).  Behavioral Reasons for Relinquishment of Dogs and Cats to 12 Shelters.  Journal of Applied Animal Welfare Science.  3:93-106.

www.vetmedcenter.com.  (2000).  Understanding Your Pet's Medical Diagnosis.  "Inappropriate Urination in Cats."  Question and Answer.

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