Feline Chronic Pain Assessment

All animals, including cats, experience chronic pain. However, signs of pain in cats are often subtle, which makes recognizing them challenging and frequently leads to cats not being prescribed analgesic medications for conditions like osteoarthritis.¹ For example, many owners are unaware that certain behavioral changes may be signs of pain (BOX 1).^2,3 Only when a behavior becomes a problem (e.g., urinating or defecating outside the litter box) is the owner most likely to bring the cat to the veterinary clinic in search of a remedy. As 1 of the 5 vital assessments along with temperature, pulse, respiration, and nutrition, pain should be routinely assessed in every patient even if the owner does not mention it.Because chronic pain develops slowly, it is the veterinary nurse’s job not only to obtain a thorough history and observe and examine cats presenting with potential pain but also to educate cat owners on signs of pain before it develops.

Categorizing Pain

Pain manifests in diverse ways. The International Association for the Study of Pain defines pain as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage.”⁴ This experience is often classified as acute or chronic and can be further broken down into 4 types (BOX 2).⁵ Chronic pain is maladaptive, which means it serves no physiologic function and has no clear endpoint. In contrast, adaptive pain is pain that warns the body of an injury or danger, such as the pain of touching a hot stove. The body automatically recognizes this type of pain and reacts immediately—in this case, by moving away from the stove.

Chronic pain may be inflammatory, neuropathic, functional, or a mixture of these types.³ Pain can also be categorized according to the disease process causing it (BOX 3).⁶ When a pet suffers from chronic pain, it can have a significant effect on the quality of life of the pet and on the human–animal bond.

Creating a Cat-Friendly Environment

Examining a cat in the veterinary clinic can be a unique challenge. A typical veterinary hospital has many smells and sounds that can further stress a cat that already does not want to be in its carrier or has taken a car ride. As a result, cats are usually very reluctant to walk normally in the exam room and tend to crouch when they do walk, not move at all, or hide. Because pain assessment relies heavily on observing movement, it is important that the cat does not perceive itself to be threatened and the cat should be allowed to dictate the terms of the interaction. Stressing a cat by restraining it or forcing it into movement will not result in a meaningful examination. It can be helpful to ask owners to bring in or send videos of how the cat acts at home when it is relaxed.

Having a quiet room the cat can be placed in on arrival can help decrease existing stress. Using synthetic feline facial pheromones in this room, either in diffusers or sprayed on a towel for the cat to lie on, can also be of help. Give the cat time to acclimate to its surroundings before beginning the physical examination, and enter the room quietly. It is important to “introduce” yourself to the cat. Open the carrier door or lid, speak quietly, and allow the cat to come out or just smell the room. Sitting quietly on the floor can help the cat feel safer. Due to the nature of cats and the need to perform the examination slowly and gently, these appointments may take a bit longer than other examinations.

Other ideas for decreasing stress during an exam include⁷:

• Allowing the cat to willingly come out of its carrier
• Having toys or treats to encourage the cat to move
• Examining the cat where it is comfortable (in the carrier with the top off, in a lap, or wrapped in a towel)

To help decrease stress created by the ride to the clinic and the examination, the veterinarian can prescribe medications for the owner to give the cat at home before the visit. If medication is given before the visit, be sure to explain to the owner any potential side effects the cat may experience, such as ataxia and sleepiness. It is also advisable to educate the owner regarding the timing to give the medication before coming to the clinic to ensure it has time to take effect.

Assessing Chronic Pain

Always watch the cat’s body language. In the hospital setting, it is helpful to observe the cat walking around the room. Is there an obvious lameness? Does the cat refuse to move? Does it sit or lie down awkwardly (e.g., not completely flexing its stifles while sitting)? Cats with chronic pain may be reluctant to run or jump, and they may not want to be pet in certain places on their body.

It is also important to ask the owner what they have observed at home, such as reluctance to eat, decreased grooming, or inability to posture in the litter box.⁸ Cats suffer from osteoarthritis, as do dogs, but they are far better at masking their pain, and the clinical signs can be subtle (FIGURE 1 AND VIDEO 1).

Figure 1. Signs of pain can be hard to recognize in cats. This cat is crouching instead of lying down comfortably.

Clinical Metrology Instruments

Several clinical metrology instruments have been developed for use in assessing chronic pain in cats (BOX 4). Some of these instruments are to be completed by the owner and some by the veterinary team. It is important to educate the owner in how to assess pain because they spend the most time with the cat while it is behaving normally. Otherwise, even if they observe subtle signs of pain at home, they may not recognize them and may disregard them.

Osteoarthritis is the most common chronic pain disorder in cats; therefore, it is the most researched in terms of validating metrology instruments.⁹ Two of these instruments, the Feline Musculoskeletal Pain Index (FMPI) and the Client-Specific Outcome Measures (CSOM), were created by the North Carolina State University Translational Research in Pain (TRiP) program for cat owners to use in assessing the severity and/or impact of pain on everyday activities. The FMPI lists 17 specific activities such as running, jumping, and playing with toys, while the CSOM allows owners to choose activities they believe are relevant to their cat’s pain and daily routine.¹⁰ The Montreal Instrument for Cat Arthritis Testing (Caretaker) (MI-CAT(C)) is also for owners or caretakers to use; it consists of 38 items to assess for arthritis pain, including agility, social behavior, grooming, and physical condition.¹¹

A related instrument, the MI-CAT(V), is for use by veterinary teams.¹² It consists of 25 different items based on physical examination and observations of the cat, including lameness, posture, and ease of movement. Another clinical tool created by TRiP, the Feline Musculoskeletal Pain, Muscle Atrophy, and Sensitivity Scoring Systems, allows the veterinarian to objectively assess pain, crepitus, thickening and effusion of joints, muscle atrophy, and muscle sensitivity using scales.¹³ This tool is more useful when assessing osteoarthritis in cats. All of these instruments can be useful in determining and quantifying pain and whether treatment provided by the veterinarian is helping to decrease these signs of pain.

Summary

Cats are incredibly good at hiding pain; however, veterinary medicine has come a long way in recognizing and treating pain in cats. Several clinical metrology instruments can be used to obtain a fuller picture of what is happening in the home environment to narrow down causes of pain. New pain therapies and scoring systems are constantly evolving and research is ongoing, allowing cats to live longer and happier lives without pain or with well-managed pain. By performing a thorough veterinary examination and educating cat owners on what to look for, the veterinary team can do a better job of treating chronic pain in cats.