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Causes for this frustrating problem fall into two categories: medical problems and behavioral problems.

Common Medical Causes of House Soiling

More common causes are listed first. Less common causes are listed later.

• Bladder infections are by far the most common cause of urinating outside of the litter box.
• Inflammation of the bladder, known as FUS or FLUTD, may cause inappropriate urination.
• Any disease that causes increased consumption of water, such as diabetes mellitus, kidney disease, or hyperthyroidism may cause cats to urinate outside of the litter box.
• Cats with arthritis or mobility disorders may have difficulty reaching the litter box, especially if long distances or stairs must be navigated each time the cat needs to urinate.
• Constipated cats may urinate outside of the box because of excessive straining during attempts to defecate.
• Exposure to certain toxins (especially pesticides) may cause urination inside the house.
• Cats may involuntarily urinate during seizures.
• Irritation of or trauma to the external genitalia very rarely causes house soiling.
• Neurological irregularities may cause house soiling.

Common Behavioral Causes of House Soiling

• Stress is the most common behavioral trigger for house soiling.
• Many cats will urinate outside of the litter box in response to the box not being kept adequately clean.
• Cats may refuse to use a litter box in which they do not feel safe.
• Cats may refuse to use a litter box that lacks privacy.
• Cats in the house may urinate in any area that has previously been soiled, due to the odor of urine in that location.
• Elderly cats may suffer from cognitive dysfunction (senility), leading to a lapse in litter box habits.
• Urinating outside of the litter box occurs as normal marking behavior in some cats. This is especially common in male cats that have not been neutered.
• Cats may be reluctant to use litter boxes that do not provide adequate privacy. A cat may refuse to use a litter box if it has been ambushed or attacked by another cat in the house while previously in the box.

Recommended Course of Action

It is critical to determine whether a medical condition is contributing to the inappropriate urination. For that reason, any cat who consistently urinates outside of the box should be assessed by a veterinarian.

Consider neutering or spaying intact cats who urinate outside of the box.

Male cats that urinate outside of the litter box may develop a life-threatening syndrome known as urinary obstruction. Any male cat that demonstrates urinary irregularities should receive immediate veterinary care.

If a veterinarian can find no medical cause for house soiling, implement a behavior modification protocol. More information on this topic can be found in the article entitled Behavioral Modification for Urinating Outside of the Litter Box.

Copyright © Eric Barchas, DVM All rights reserved.
The contents of this page are provided for general informational purposes only. Under no circumstances should this page be substituted for professional consultation with a veterinarian.