What is anorexia?
Anorexia is a decrease or loss of appetite for food. While hunger is physically driven, appetite is mentally driven.
"Decreased appetite and decreased food intake may indicate potentially life-threatening underlying conditions and should be taken seriously."
There are two types of anorexia: true anorexia and 'pseudo-anorexia.' Both result in decreased food intake, but a dog with pseudo-anorexia wants to eat (is hungry), but is unable to because of difficulty picking up, chewing, or swallowing food or some other cause (see below). Regardless of whether a dog is dealing with true or pseudo-anorexia, decreased appetite and decreased food intake are outward signs that should be taken seriously. These signs may indicate potentially life-threatening underlying conditions. Poor appetite or refusal to eat is strongly associated with illness and is a common reason for dog owners to seek veterinary care.
What causes anorexia and pseudo-anorexia?
There are many potential explanations for decreased food consumption, and the first, most important step is to determine whether the dog has true or pseudo-anorexia. Does he want to eat but is unable to, or is he truly not interested in eating?
"There are many potential explanations for decreased food consumption, and the first, most important step is to determine whether the dog has true or pseudo-anorexia."
Your veterinarian will want to take a detailed history to begin to differentiate between the two conditions. Next your dog will have a thorough physical examination to try to determine the presence of an obvious physical explanation for decreased food consumption. Finally, diagnostic tests will be used to aid in uncovering a reason for decreased appetite. These may include laboratory tests such as a complete blood count (CBC) and a serum chemistry profile, electrolytes (checks mineral balance), radiographs (X-rays) of the chest and abdomen, ultrasound studies, and (depending on other findings), more invasive diagnostics like endoscopy or biopsies.
Potential explanations for pseudo-anorexia in which a dog wants to eat but does not or has difficulty eating include:
- Stomatitis, gingivitis, or esophagitis; inflammation and pain within the tissues of the mouth and throat.
- Advanced periodontal disease, which may include loose teeth.
- An abscess behind the eye.
- Pain in the mastication (chewing) muscles.
- Pain in the temporomandibular joint (TMJ); the two joints connecting the jawbone to the skull.
- Salivary gland disease.
- Nervous system disease affecting chewing and swallowing.
- Cancer or tumors of the mouth, tongue, tonsil, or associated structures.
- Pain anywhere in the body. Chronic pain is very distracting and may interfere with appetite or with the dog’s ability to reach his food and water dishes on the floor if, for instance, he is dealing with back pain.
True anorexia can also have various causes:
- Systemic disease, whether it involves infection or an organ system dysfunction (e.g., diabetes or kidney disease), can lead to anorexia.
- Psychological explanations, such as stress, altered routines, changes in the environment, or undesirable/unpalatable food.
- Exposure to poisons.
- Immune system imbalance/disease.
- Inability to smell. Scent is an important contributor to palatability of food and appetite.
- Any painful condition can suppress appetite.
- Cancers of all types.
- Gastrointestinal (GI) blockage.
- Stomach or intestinal ulcer.
- Nausea from any cause.
- High environmental temperature.
- Medication side effects.
How are anorexia and pseudo-anorexia treated?
Treatment will depend on what the diagnosis is. Associated or additional treatment will focus on treating/managing related symptoms. For instance, if the dog is dehydrated, then intravenous fluids may be needed. Any nausea must be eliminated. If it is appropriate, your veterinarian may prescribe a short-term appetite stimulant such as cyproheptadine (brand name Periactin®) or mirtazapine (brand names Remeron®, Mirataz®). In the United States, a newer medication called capromorelin (brand name Entyce®) has been developed and has shown good success. If there is a mineral imbalance like low potassium, which can interfere with normal appetite, then a potassium supplement will be added. It may be useful to enhance the palatability of your dog's food. Your veterinarian can help you with specific recommendations, but simple steps to try include:
- Adding a canned formulation to the diet.
- Heating food to approximately body temperature (~100°F [38°C]) **Note: If heating in the microwave, stir the food to ensure no hot pockets are left.
- Adding a bit of low-sodium chicken, vegetable, or beef broth for flavor enhancement.
- Temporarily preparing a home cooked diet with guidance from your veterinarian as to appropriate recipes.
Occasionally, an anorectic dog who has an underlying metabolic disorder must receive nutrients but is unwilling to eat. In these cases, it may be necessary for your veterinarian to place a feeding tube into the nostril, stomach, or small intestine through a small incision in the skin. Feeding tubes are generally not considered heroic interventions, but they are nearly always lifesaving. Food and medication can be delivered with very little stress on the dog. If the GI system is capable of digestion, it should be used, even if that means delivering food through a tube for a while.
If the GI system is not working for some reason, your veterinarian may recommend what is called parenteral feeding, in which nutrition is provided intravenously. Parenteral feeding is a specialized, complicated technique generally performed by a specialist in a referral center. Tube feeding and parenteral nutrition are most often undertaken as ’bridge’ procedures until the dog can eat on his own.
What is my takeaway message?
Regardless of the reason for decreased food intake, changes in eating habits and patterns warrant investigation. Lost or decreased appetite may signal something serious and may contribute to a serious consequence or outcome. Take changes in your dog's eating behavior seriously, and get your veterinarian involved early.