Jean Duddy, DVM
Veterinarians are commonly presented with the cat that has ‘lost their appetite.’ There are many different scenarios that may bring this complaint to our office. For some owners feeding may be a bonding time with their cat and missing one or two meals may bring them to our office. Other cats ‘free feed’ dry food and a decrease in appetite may not be noticed for an extended period of time. So the presentation of the cats can be very different from no abnormal physical findings to significant weight loss.
To complicate matters there are a number of terms associated with a decrease in appetite. Anorexia is the lack of or loss of appetite and it can be partial or complete. Inappetence also known as hyporexia is a decrease in appetite.
True anorexia (lack of appetite) can be divided into primary and secondary anorexia:
Primary – (directly causing the lack of appetite)
- Neurologic (changing the appetite center in the hypothalamus directly)
- Lack of smell (Anosmia)
- Behavioral (environmental changes, fear or anxiety)
Secondary – (any disease or process that disrupts the normal hunger response)
- Systemic disease
- Infectious diseases causing dehydration, fever, etc
- Pyelonephritis, pancreatitis, etc. may cause nausea
- Respiratory diseases – upper decreases smell, lower makes them unable to breathe normally
- Pain (infections, abscess, trauma, arthritis, dental disease, neoplasia, etc.)
- Neoplasia (via chemical mediators)
- Drugs (many drugs decrease appetite directly)
- Chemotherapy drugs cause nausea
- Opioids inhibit orexigenic (appetite stimulating) pathway
Pseudoanorexia – is not a lack of appetite, but the cat cannot eat for other reasons:
- Pain from oral/dental disease
- Problems prehending food due to neurologic disease
- Dietary – unpalatable diet
- Environmental – repeatedly attacked at the food bowl/not able to get to the food bowl
The approach to the cat presented with a decreased appetite must start with a complete history from the owner. Trying to determine if it is hyporexia or anorexia can be difficult. Even determining if the loss of appetitie was a slow change or acute decrease in appetite can be hard for owners to know for sure.
Some of the important questions for owners include:
Past/present illnesses and recent or current medications (including doses to be sure the dose is appropriate). Do not forget to inquire about supplements. Many owners do not consider supplements when giving their history of what they are giving to their cats.
Changes in environment such as dietary change, change in location of available foods, addition or loss of any animals or people in the household. Sometimes changes in routines of the owners can be important.
A full physical exam should be done looking for any obvious abnormalities that could cause a loss of appetite. Particular importance should be placed on oral or GI abnormalities but any organ system can be the cause of anorexia, (vestibular disease can cause nausea, ocular disease can cause pain, etc.).
The clinical picture will help you determine what is required for a diagnostic evaluation. A minimum data base (CBC, biochemical profile, urinalysis) should be done in almost all cases. These tests can help determine the cause of the loss of appetite, but also indicate how the cat is handling inadequate nutrition. Some anorectic cats may develop hypokalemia which can increase lethargy and worsen appetite. Other tests may be indicated based on the results of the initial tests.
Ancillary tests may include (but are definitely not limited to):
- Urine Culture if bacteriuria or if dilute
- T4 +/- elevated liver enzymes
- Toxoplasmosis with elevated CK and appropriate history.
- Feline Pancreatic Lipase (may have mild hypocalcemia or no abnormalities at all)
- Blood Pressure
- Diagnostic imaging – radiographs, abdominal ultrasound.
The best treatment for anorexia is a quick diagnosis and correction of the underlying etiology of the decreased or absent appetite. Nutritional support should be provided if it is likely the cat will continue to have anorexia for a prolonged period of time or if the cat has had anorexia for more than 3 days to prevent hepatic lipidosis. Nutritional support also should be considered in cachectic patients, patients with protein-losing diseases, (such as peritonitis, pyothorax or burns), or acute loss of more than 10% body weight regardless of the cause. Nutritional support will help speed recovery and decrease morbidity and mortality.
Along with nutritional support it is important to correct dehydration and electrolyte abnormalities. Other important factors to evaluate are if the cat is showing signs of nausea or pain. Nausea can be a powerful cause of anorexia. Treatment with anti-emetics such as maropitant (0.5-1.0mg/kg once daily) or metoclopramide continuous IV infusion at 1-2mg/kg/day can be initiated. If no cause for the anorexia has been found, a trial with analgesics is warranted. Sublingual buprenorphine 0.01–0.02 mg/kg q6–12h may relieve discomfort and allow your client to see if their cat’s appetite improves.
Once hydration, electrolytes, nausea and pain are adequately treated, you can decide what form of nutritional support to use. Whenever possible use the GI tract. Enteral nutrition is preferable over parenteral nutrition. Our goal is to prevent atrophy of the enterocytes of the intestine. Enterocytes get half of their nutrients directly from the intestinal lumen. In anorexic cats these cells are hypoplastic and hypofunctional with increased permeability. This can lead to many secondary problems.
Tempting a cat to eat is more of an art then a science. There is no one thing that works for every cat. Here are some things to keep in mind:
- Feed small amounts at one time. Some cats will respond to a variety, but too much food presented at one time may overwhelm the cat’s senses and actually turn them off.
- Try to feed other foods they are not normally fed. If the cat got sick after eating their normal food, it may result in food aversion in that cat. In simple cases, feeding a different flavor or a different texture (shreds instead of pate) or treats may be enough to stimulate the appetite. Others may respond to human foods such as deli turkey or tuna fish.
- To enhance the smell, you can warm some canned foods. If the smell seems to stimulate nausea, try dry food or foods with little smell (strained meat baby foods).
- Many cats like catnip and sprinkling a small amount on the top of food will stimulate them to eat the catnip and may jumpstart eating the food.
Syringe or “force” feeding can be used, but this can be stressful and even lead to food aversion. Cats often will drool and fight anything being placed in their mouth. Obtaining adequate calories can be difficult so this is mainly used to get the taste of food in their mouth in hopes of jumpstarting their own appetite.
Appetite stimulants are now used commonly, but are best used after dehydration, nausea and pain have been treated.
Cyproheptadine (Periactin) – (0.1-0.5mg/kg BID to TID)
Antihistamine with serotonin antagonist effects
May take 3 days to reach therapeutic levels and should be tapered to stop
Side effects can be lethargy or even agitation
Mirtazipine 1.875mg q 48hr or 3.75mg q 72 hour (liquid from is very bitter)
Adrenergic and serotonergic antidepressant, antiemetic, anti-nausea
Effects usually within an hour of admission
Side effects can include hypertension, drowsiness, vocalization, and Serotinin Syndrome (diarrhea, ataxia, tachycardia, tremors and fever). Use caution with high doses or with other serotonergic drugs
Tube feeding – can be less stressful and increases our ability to consistently get food into an anorexic cat. Each type of tube has pros and cons that should be considered.
Naso-esophageal (NE) tube: These tubes are easily placed and can be used immediately. These tubes have limitations such as; they cannot be used in vomiting cats, they are likely only tolerated for a short time and only liquid diets can be used because the tubes are so small.
Esophageal (E) tube: Allows longterm feeding of a gruel consistency food. An E tube does require a short general anesthesia for placment. The tube can be used several hours after placement and can be removed at any time when not required. An E tube should not be used in vomiting cats.
Gastrostomy (G) tube: Allows long term feeding of canned/gruel foods. Also should not be used in vomiting cats. Anesthesia is required and , placement techniques include:
- Surgical at the same time an exploratory laparotomy is done.
- Pecutaneous endoscopically placed gastrostomay (PEG) tube.
- Blind placement (greater chance of complications)
The tube must be in place for 10-14 days before safe removal and leakage around the tube could cause peritonitis.
Jejunostomy (J) tube: Not used commonly, usually placed with exploratory laparotomy, used to bypass the stomach (gastric disease or pancreatitis) where the SI function is normal.
Calculating how much to feed can be difficult because disease states can increase a cat’s nutritional needs. Critical care specialists have estimated additional nutritional needs as multiples of the resting energy requirement (RER).
RER = 70 x (current bodyweight in kilograms)0.75 (for > 5 kg)
RER = 30 x BWkg +70 (for < 5 kg)
Which diet to feed may be limited by the tube if you are using for tube feeding. First, the diet should have enough calories, protein and micro-nutrients. The disease process will need to be considered. Many of the common diets we use with tubes are:
Peptamin 1.5 kcal/ml
Clinicare 1.0 kcal/ml
Hills a/d 1.3 kcal/ml
RC MediCal Recovery 1.2 kcal/ml
Euk Max Calorie 2.1 kcal/ml
Once a feeding tube is placed, removal in part is dictated by the type of tube used. It is generally a good idea to wean off of the tube feedings as the patient begins to eat. It is also best to have them off of the appetite stimulants prior to removing feeding tube support. Once the cat is eating normally for a week, the feeding tube can be removed. This timeline may need to be altered if the tube is not being tolerated for any reason.
For more information, contact Angell’s Internal Medicine service at 617-541-5186 or firstname.lastname@example.org.