Chronic pain is not a singular disease. It takes on many different forms and occurs for many various reasons, with a variety of specific depictions. Under-recognised and under-managed chronic pain can result in death via humane euthanasia, perhaps years earlier than would otherwise be necessary. Thus, the recognition and management of chronic pain—in whatever form—is equally as life-preserving as any actions taken to handle acute and critical conditions in veterinary patients. Untreated chronic pain is unbearable and debilitating, greatly diminishing the quality of life of dogs and cats. Management of chronic pain is multifactorial, comprising diet, lifestyle changes, and proper use of medication.
Types of chronic pain in animals
In animals, chronic pain is common in the following conditions:
2. Chronic or chronic–active inflammatory pain not related to osteoarthritis
a. Chronic periodontal disease
b. Feline lymphocytic—plasmacytic stomatitis
c. Idiopathic feline lower urinary tract disease
d. Inflammatory bowel disease
e. Meningoencephalitides
f. Otitis external
g. Pancreatitis
3. Maladaptive chronic pain not associated with osteoarthritis or cancer
a. Central nervous system lesions, including post-trauma or vascular accidents,
intracranial masses, and inherited disabilities (e.g., syringomyelia)
b. Chronic intervertebral disk disease
c. Diabetic neuropathy
d. Feline hyperesthesia syndrome
e. Feline orofacial pain syndrome
f. Post-peripheral nerve injury (e.g., trauma, amputation)
g. Post-surgical conditions (e.g., fractures, hernia repair)
h. Others
4. Cancer pain, especially osteosarcoma or other bone metastasis.
Assessment of Pain
Assessment of pain in veterinary patients is a challenge. Firstly, the patient needs to be assessed by looking at the patient’s communication and behaviour with its owners, with the doctor, and with the staff.
Is the patient guarding the affected area?
Is the patient reluctant to move and interact?
Is the patient’s attitude and interaction typical, based on past experience with that pet?
A physical examination is then performed and palpation-induced pain assessed. The owner is afterwards quizzed on the day-to-day activity of the pet, the pet’s ability to ambulate well, the pet’s quality of sleep and appetite, and the pet’s participation in favourite activities, e.g., greeting the owner at the door, eating, chasing a ball or other toy, or playing with the family. It is crucial to know if the pet is still active in these things. If not, then this is a sign that the patient’s quality of life may not be optimal.
Signs of pain in Dogs
Tail between the legs
Arched or hunched back
Reluctance to move
Drooped head
Protection of the painful area
Aggression or irritability
Growling or biting, especially when the painful area is touched
Hiding or trying to escape
Howling, moaning, or whimpering
Carrying one leg
Limping
Bizarre gait
Inability to walk
Unwillingness or lack of ability to jump
Little interest in food or play
Chewing or licking the painful area
Signs of pain in Cats
Tucked belly or legs
Arched or hunched head or back
Reluctance to move
Drooped head
Slumped body
Aggression, irritability, or biting
Hiding or trying to escape
Crying, screaming, or moaning
Hissing or spitting
Carrying one leg
Limping
Bizarre gait
Inability to walk
Reluctance or inability to jump
Attacking or hissing, especially when the painful area is touched
Failure to groom
Dilated pupils
Little interest in food or play
Effects of Chronic Pain
Significant unrelieved pain is a stressor that causes distress and negative physiologic consequences, not the least of which is immune dysfunction. Unrelieved pain also has specific effects on animal behaviour such as reductions in food and water intake or body weight (a surrogate marker of oral intake). In many instances, the administration of analgesics (pain killers) reduces the magnitude of these changes. Other adverse effects of pain and the morbidity it causes include ileus (a painful obstruction of the ileum or other part of the intestine), impaired respiratory function and tissue oxygenation. Pain relief is, therefore, good for animal welfare and wellbeing.
Further Reading
References
[1] K. A. Mathews, “Neuropathic pain in dogs and cats: if only they could tell us if they hurt,” Veterinary Clinics of North America: Small Animal Practice, vol. 38, no. 6, pp. 1365-1414, 2008.
[2] L. Ray, R. B. Lipton, M. E. Zimmerman, M. J. Katz and C. A. Derby, “Mechanisms of association between obesity and chronic pain in the elderly,” PAIN®, vol. 152, no. 1, pp. 53-59., 2011.
[3] R. A. Gupta and R. N. DuBois, “Colorectal cancer prevention and treatment by inhibition of cyclooxygenase-2,” Nature Reviews Cancer, vol. 1, pp. 11-21, 2001.
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[5] L. I. Slingerland, H. A. W. Hazewinkel, B. P. P. P. Meij and G. Voorhout, “Cross-sectional study of the prevalence and clinical features of osteoarthritis in 100 cats.,” The Veterinary Journal, vol. 187, no. 3, pp. 304-309, 2011.
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[7] K. A. Kirkby and D. D. Lewis, “Canine hip dysplasia: reviewing the evidence for nonsurgical management.,” Veterinary Surgery,, vol. 41, no. 1, 2012.
[8] R. J. Corbee, M. M. C. Barnier, C. H. A. Van De Lest and H. A. W. Hazewinkel, “The effect of dietary long‐chain omega‐3 fatty acid supplementation on owner’s perception of behaviour and locomotion in cats with naturally occurring osteoarthritis.,” Journal of animal physiology and animal nutrition,, vol. 97, no. 5, pp. 846-853, 2013.