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House soiling in cats occurs when they urinate or defecate outside their litter box. Urination or defecation (pooping) outside the litter box falls into two categories: toileting and marking. Toileting often indicates an underlying medical condition or incomplete litter box training. Marking, or middening, occurs when a cat uses feces instead of urine to make a statement or communicate. While less common than urine marking, both marking behaviors are normal (although undesirable to humans) and often serve as a way for cats to express themselves or send a message.

Medical Reasons for House Soiling (Feces)

If your cat is defecating outside the litter box, consult your veterinarian to check for medical causes, such as osteoarthritis or other sources of pain. Osteoarthritis, a common but often overlooked condition, can lead to discomfort and behavioral changes, including house soiling. Research shows that many cats, particularly those who are overweight, develop arthritis as they age. This condition can make activities like stepping into a high-sided litter box, climbing stairs, or jumping off furniture uncomfortable or even painful. As a result, cats may choose to defecate on the floor near the litter box or closer to their resting areas, such as on the bed.

Diagnosing Arthritis in Cats

Cats are experts at hiding pain, so diagnosing osteoarthritis often requires more than just a physical exam. Observations at home are particularly useful—video recordings of your cat’s movements and behaviors can provide valuable information about mobility and discomfort. Orthopedic evaluations often incorporate these at-home observations to get a complete picture. In some cases, administering pain medications under your veterinarian’s guidance can serve as a diagnostic tool and a way to relieve discomfort.

Other Medical Conditions to Consider

Other medical conditions can contribute to house soiling. These include:

• Neurological disorders that cause pain or affect the cat's ability to control defecation
• Gastrointestinal diseases and intestinal parasites may cause soft or hard stools, painful defecation, or intermittent abdominal pain

Diagnostic Tools and Procedures

Various diagnostic methods can help pinpoint the underlying cause of house soiling:

• Fecal flotation and specialized tests to detect intestinal parasites
• Routine or specialized bloodwork to evaluate overall health and gastrointestinal function
• Diagnostic imaging, including X-rays and ultrasounds, to assess internal structures
• Endoscopy and colonoscopy for a detailed examination of the upper and lower gastrointestinal tract
• MRI to check for spinal cord entrapment, injury, or disk disease
• Dietary trials to identify food sensitivities or allergies that may contribute to gastrointestinal issues

Behavioral Reasons for House Soiling

If medical issues are ruled out or treated but house soiling persists, the next step is investigating behavioral causes. Understanding your cat’s habits, preferences, and environment can provide insight into the problem.

House soiling can occur if a cat is not fully litter box trained or if they are accustomed to eliminating outdoors but no longer have access. In other cases, the litter box itself may be the issue. Cats are sensitive about their bathroom setup, and small changes can have a big impact.

Common litter box issues include:

• The box is not cleaned often enough.
• The box is in an undesirable or inconvenient location.
• The type of litter does not match your cat’s preferences (e.g., texture, scent, or material).
• The box is too small for the cat to turn around or posture comfortably.
• The box has high sides, a top entry, or is covered.
• The litter depth is too shallow or too deep.
• The box has been cleaned with strong-smelling products like citrus, woodsy, or perfumy scented cleaners, which cats dislike.
• A liner is used, and the plastic gets caught in the cat’s nails while digging.
• The box is too close to the food and water dishes.
• Access to the box is blocked by another cat, dog, or person.
• There are not enough litter boxes, or they are located in inconvenient spots, such as on another floor or near a noisy furnace or appliance.

Environmental stressors, such as tense relationships with other pets, children, or family members, can also contribute to house soiling. Cats are territorial and selectively social. Marking behaviors (using urine or feces) may be their way of claiming space or expressing anxiety. Fear or separation-related behaviors may also play a role.

Treatment Option

A thorough behavioral history, combined with adjustments to the home environment, can help address house soiling. Start by mapping your home to identify problem areas and stressors and observe your cat’s interactions with others in the household. 

These steps can help reveal the reasons behind the behavior.

Optimizing the Litter Box Setup

Improving the litter box setup can significantly reduce house soiling:

• Block undesirable areas where your cat defecates and make the litter box more appealing.
• Clean soiled areas promptly with enzyme-based cleaners to remove lingering odors.
• Scoop the litter box daily and refresh the litter regularly. Empty, clean, and refill the box every 1-2 weeks.
• Provide enough litter boxes—one per cat plus one extra. Place them on each floor of the house and use boxes large enough for your cat to turn around comfortably.
• Experiment with different litter types, box styles, and litter depths to discover what your cat prefers.
• Use window film and other deterrents in the yard to reduce outside triggers, such as stress from outdoor cats.
• Provide a lower-sided box to help cats with osteoarthritis.

Reducing Stress and Mental Enrichment

Addressing environmental factors and providing mental stimulation can help:

• Use food-dispensing toys and puzzles to engage your cat in natural hunting and problem-solving activities, which can reduce stress and build confidence.
• Avoid punishment. Instead, use positive reinforcement to encourage desirable behaviors and strengthen your bond with your cat.
• Take steps to reduce interpersonal stress between your cat and other pets or family members.

Managing Emotional and Behavioral Disorders

If emotional factors such as fear, noise phobias, or separation-related behaviors contribute to house-soiling, additional interventions may be needed. Anti-anxiety medications or supplements can sometimes help, but these can be difficult to administer and are best considered after exploring other potential causes. This does not mean these medications are harmful but addressing medical and environmental factors first often provides a clearer understanding of the issue.

Conclusion

House soiling in cats often requires thorough investigation and a step-by-step approach to identify medical, behavioral, or environmental causes. While some cases may not be fully resolved, addressing these factors can reduce the frequency of the behavior. Collaboration with your veterinarian and a well-thought-out plan can make managing house soiling more effective.