Statement of the Problem

A cat was evaluated because of urinating outside the litter box and aggression toward the other household cat.

Signalment

The patient (cat A) was a 3-year-old castrated male domestic shorthair cat.

History

Cat A had been acquired from a shelter at 5 months of age. At that time, the owner already owned a 1-year-old spayed female domestic shorthair cat (cat B). Soon after cat A was adopted, it would squat every 2 to 3 weeks to urinate in large volumes on various horizontal substrates in all rooms throughout the house. This behavior escalated when human visitors stayed at the house. The owner had had a wedding at her house 2 months prior to examination by the behavioral service, and after this, cat A started urinating outside the litter box 2 to 4 times daily. The inappropriate urination included a combination of squatting to urinate in large amounts on various horizontal surfaces and standing with an erect quivering tail to urinate small amounts on vertical surfaces (eg, window sills, appliances, the arm of a chair, and a tree under which a stray cat often sat). Cat A also followed stray cats from window to window from inside the home. Cat B was never observed by the owner to urinate outside the litter box, and both cats defecated in the litter box. Cat A was not observed to dig in the litter before eliminating, and the cats were never observed to block the boxes from one another. There were 2 standard, although small, covered litter boxes with scented, clumping clay litter^a: 1 in the office and 1 that had originally been located in the bedroom but was later moved to the dining room. The boxes were scooped daily. The owner cleaned the boxes with water and mild soap every 3 months; immediately after each cleaning, cat A ran to and eliminated in the boxes. Soiled areas were cleaned with water, a nonenzymatic multisurface cleaner,^b or an enzymatic, bacterial cleaner.^c The owner tried unsuccessfully to improve cat A's house soiling through the use of a pheromone diffuser^d and by offering both covered and uncovered litter boxes, moving litter box locations, placing plastic under a couch cover, spraying a citrus scent in soiled areas, and placing bowls of food in soiled areas.

Additionally, over the past year, cat A had begun chasing cat B away when cat B slept in the cat bed in the office, sometimes when cat B ate at the food bowl, and when cat B approached cat A while cat A rested. Cat A would chase cat B for short distances every other night and would corner and hiss at cat B while making direct eye contact with a forward, confident body posture. Cat B would calmly move away without hissing or growling. The cats never allogroomed or slept together. When the owner fed them treats together, cat A would hiss if cat B approached it. When cat A was allowed part-time outdoor access, during those times it was indoors, it more frequently urinated small volumes on vertical surfaces and chased cat B less often.

One year prior to examination by the behavior service, results of a urinalysis performed by the referring veterinarian were within reference limits, and results of bacterial culture of a urine sample were negative. At that time, alprazolam (0.044 mg/kg [0.02 mg/lb], PO, q 12 h for 1 month), a benzodiazepine, was prescribed but caused ataxia. A reduction in the dosage (0.022 mg/kg [0.01 mg/lb], PO, q 12 h for 1 month) resolved the ataxia, but did not improve the frequency of urinating around the house. Prednisone (0.44 mg/kg [0.20 mg/lb], PO, q 24 h), a corticosteroid, was given concurrently with alprazolam for 1 month. Both medications had been discontinued at the time of examination by the behavior service owing to a lack of improvement in cat A's urinating outside the litter box.

Physical Examination Findings and Laboratory Results

Cat A did not exit its open carrier willingly during the appointment. When gently lifted from its carrier, the cat was stiff and clung to the table with eyes dilated and a hunched body posture. Results of a physical examination, CBC, serum biochemical panel, urinalysis, and bacterial culture of a urine sample were all unremarkable.

Diagnosis

Diagnoses of urine marking, inappropriate urination, and status aggression (toward cat B) were made. The diagnosis of urine marking was made on the basis of the fact that while in the typical urine marking posture (standing with an erect quivering tail), cat A deposited small volumes of urine on vertical surfaces in socially important locations. Urine marking is a normal form of communication in cats.^1–4 Cats that urine mark have been described as being in a state of heightened emotional arousal because of territorial behavior, anxiety, or stress in response to human visitors, outdoor animals, or tension among household cats, which all occurred in this household.^1,2

In addition, cat A also squatted to urinate large amounts on horizontal surfaces outside the litter box, supporting the diagnosis of inappropriate urination, a toileting behavior.^1,2 The lack of response to previous litter substrate, litter box location, and other litter box changes made by the owner, along with a pattern of eliminating on varied surfaces, also suggested a possible diagnosis of urine marking rather than a straightforward toileting problem. Possible causes that were considered included various medical and behavioral conditions. However, conditions such as renal, lower urinary tract (urolithiasis, cystitis, and infection), endocrine (diabetes mellitus), musculoskeletal (arthritis), infectious, and neoplastic diseases were considered unlikely because of the lack of compatible clinical signs (eg, pollakiuria, dysuria, stranguria, or hematuria) in combination with normal laboratory test and physical examination findings. If warranted, abdominal radiography, ultrasonography, and cystoscopy could have been used to help rule out urolithiasis and idiopathic cystitis as contributing causes.^2,5

Behavioral causes of inappropriate urination on horizontal surfaces include anxiety, aversions, and preferences.¹ Likely causes for cat A's urination on horizontal surfaces included anxiety and litter box and substrate aversion secondary to use of an undesirable litter type and inadequate hygiene. Anxiety may have been caused by human visitors and tension between household cats, the former of which coincided with an increase in house soiling. Cat A seemed to prefer a spotless litter box, as the cat eliminated in the boxes immediately after they were thoroughly cleaned. The small size of the litter boxes combined with untimely thorough cleaning supported the possibility of litter box aversion as a contributing cause.² Cat A did not dig in the litter before eliminating, which has been reported previously for cats with elimination problems⁶ and may indicate a substrate aversion. Aversion to the scent of the litter was also possible. One study found scented litter to be a risk factor for elimination problems⁷ while another did not.⁶ Cat A urinated on various substrates throughout the house, including various locations in the rooms where the litter boxes were located, making a substrate preference, location preference, and location aversion unlikely. Importantly, cat A's inappropriate urination on horizontal surfaces could also have been consistent with a diagnosis of urine marking. Most cats, including cat A, with inappropriate urination continue to occasionally use the litter box for elimination.¹

Possible causes of cat A's aggression (ie, chasing and hissing) toward cat B that were considered included status aggression, territorial aggression, fear aggression, redirected aggression, and play aggression.^8,9 Cat A chased and hissed at cat B with confident body postures, displacing cat B from preferred resources; this behavior began at social maturity, supporting a diagnosis of status aggression.^8–10 Territorial aggression was possible, as cat A chased cat B from specific sites⁸; however, the 2 cats initially got along well for over a year, and cat A chased cat B only a short distance.¹¹ Cat A's body postures toward cat B had always been forward and confident, ruling out fear aggression.^8,9 Cat A vocalized and did not display predatory-type play behavior toward cat B, ruling out play aggression.⁹ Cat B was the original target for cat A's aggressive arousal, ruling out redirected aggression.⁹ Medical causes were unlikely on the basis of normal physical examination findings and laboratory test results.

Treatment

Avoidance of the triggers causing arousal was the first step in treating cat A's urine marking behavior^1,12 and status aggression^8,9 toward cat B. This involved keeping cat A completely indoors because the urine marking escalated when cat A was allowed outside, blocking exposure to outdoor cats, and using motion-activated sprinklers to deter outdoor cats. The owner was instructed to keep cat A and cat B separated when not closely supervised and avoid known aggressive triggers when they were supervised. Systematic desensitization and counterconditioning (DSCC) was recommended to help decrease aggression between the household cats; however, DSCC was not practical to decrease aggression directed toward stray cats.⁹ During DSCC, cat A and cat B were to be fed a palatable treat or engaged in play with the owner while the 2 cats were a distance from each other where they remained calm.⁹ Over many sessions, the distance between the cats was to be reduced. If the cats showed any negative behavior, their distance was to be increased so that they could be rewarded for relaxed behavior. Apart from the sessions, the owner was recommended to toss a magazine as a disruptive stimulus as soon as cat A began chasing cat B and then reward calm behavior if this did not cause increased anxiety or aggression.⁹ Physical punishment was contraindicated owing to the risk that the cats would develop fear and defensive aggression.⁹ To decrease overall stress and facilitate other activities, providing environmental enrichment such as food-dispensing toys and more resting, hiding, feeding, climbing, and perching areas was suggested.^9,13,14

Environmental management significantly improves urine marking¹⁵ and was indicated to treat cat A's litter box aversion.^1,2,12 The owner was directed to continue to scoop the litter boxes daily, but increase the frequency of thorough cleaning with water and mild soap to once weekly.^2,12 Three litter boxes (1 plus the number of cats in the household) were to be placed throughout the home.¹ A litter box length of 1.5 times the length of the cat was recommended,¹ with under-bed storage boxes suggested as new litter boxes. Because urine odors can be attractive to cats, an enzymatic cleaner^e was recommended for soiled areas as the most effective way to remove the odors.^2,16 Use of a black light on a daily schedule was recommended to help locate urine outside the box,¹⁶ so that the owner could clean the areas and note reoccurrences of urine deposition on vertical and horizontal surfaces. Options for environmental management of previously soiled areas included making them inaccessible, making them aversive with upside-down carpet runners or contact paper, or changing their importance by putting the cats' beds or litter boxes in the areas.² To ensure use of litter that cat A found attractive, a preference trial was recommended. At times cat A was likely to eliminate, the cat was to be confined in an area containing 3 litter boxes, with each box containing 1 of 3 litter types: the current litter; an unscented, carbon-activated, clumping litter^f; and a corn-based litter.^g The owner was asked to note cat A's litter preference over a 2-week trial period. The owner was encouraged to reward cat A with praise or food immediately after it was observed urinating in the box.² Pheromones have been shown to reduce urine marking,^17,18 but were previously unsuccessful in reducing cat A's urine marking, and a recent review¹⁹ found that success rates may have been overestimated in these studies. Scratching posts and cheek-marking items^h were recommended as a way to encourage other forms of marking and potentially decrease the incidence of urine marking.¹²

Medication is often indicated for treatment of urine marking in cats.² The most effective options have been shown to be fluoxetine, a selective serotonin reuptake inhibitor, and clomipramine, a tricyclic antidepressant.^20,21 The response to treatment can be rapid with a decline in urine marking within days to weeks of treatment initiation.^1,20,21 To decrease cat A's reactivity to social and environmental stimuli, fluoxetineⁱ was prescribed at a dosage of 0.35 mg/kg (0.16 mg/lb), PO, once daily for 7 days, to be increased to 0.70 mg/kg (0.32 mg/lb), PO, once daily thereafter if no adverse effects were noted. Fluoxetine was chosen because selective serotonin reuptake inhibitors generally have fewer adverse effects than tricyclic antidepressants.²² Tests of hepatic and renal function were performed before treatment with fluoxetine was initiated and were found to be within reference limits. Concerns related to extralabel use and the risk of adverse effects, including aggression, were discussed with the owner prior to initiation of treatment.²³

Follow-up

During a 1-month follow-up telephone call, the owner reported that cat A had urine marked only 3 times and had not urinated on horizontal surfaces outside the boxes in the previous month. Cat A seemed to prefer the litter boxes and the unscented clumping litter, although a litter preference trial had not been conducted as recommended. Cat A was kept indoors only. During daily DSCC sessions, the distance between the household cats was decreased from 6.1 to 4.6 m (20 to 15 feet) over the month, but cat A still chased cat B nightly when unsupervised. When the owner tossed a magazine nearby, cat A would stop chasing cat B and go back to its own bed. Neither cat was described as being fearful of the tossed magazine. Closer supervision and separation when not supervised were suggested. Fluoxetine administration was continued at a dosage of 0.70 mg/kg, PO, every 24 hours, with no adverse effects noted.

During a 4-month follow-up telephone call, the owner reported that cat A had continued to improve. Urine marking was limited to once monthly when cat A saw a stray cat outside, which was acceptable to the owner. Cat A dug in the litter before eliminating and urinated only in the litter box. Cat A and cat B ate and played calmly within 1.5 m (5 feet) of each other during DSCC sessions. A new cat tree and cat beds had been added. Cat A chased cat B only once weekly when the owner was not supervising them at night. Improvement in all behaviors was stable from months 2 to 4, so the dosage of fluoxetine was decreased by 25%.²³

During a 6-month follow-up telephone call, the owner reported that cat A had not been receiving fluoxetine for 1 month. Cat A continued to urinate only in the litter box, urine mark monthly when the cat saw a stray cat outside, and chase cat B weekly. The owner continued environmental and behavior modification to maintain success without fluoxetine administration.¹