Stomach Tumors in Dogs and Cats

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Article Written by Dr. Daniel A. Degner, Board-certified Veterinary Surgeon (DACVS)

Animal Surgical Center of Michigan

5045 Miller Road

Flint, MI 48507

Phone: 810-671-0088

Key Points

Stomach tumors commonly are malignant

Surgical removal of the tumor is largely palliative

Prognosis is guarded, however, surgery may help relieve tumor-associated symptoms


The gastrointestinal tract consists of a tube that runs from the mouth to the anus. Its function is to digest food and absorb nutrients into the body. The stomach is a dilated part of the GI tract that produces acids which helps with initial breakdown of proteins. The small intestine extends from the stomach to the colon and serves to further breakdown food into absorbable nutrients. The cells lining the small intestine are distinctly different from that of the stomach.



Stomach cancer

Cancer can develop in the stomach in dogs, but rarely in cats. There are two major types of cancer that affect the stomach: benign and malignant. The cancer of the stomach usually is malignant and has a high tendency to spread to other parts of the body. If it spreads, the liver and the lymph nodes are commonly affected, however, the tumor can also spread to the lungs. Lymphoma (commonly in the feline species), adenocarcinoma and leiomyosarcoma comprise the majority of malignant stomach tumors. Benign leiomyomas such as extramedullary plasmacytoma and leiomyomacan also affect the stomach, are easily treated with surgery and have a very good prognosis.




Breeds that more commonly develop stomach cancer include the Rough Collie, Staffordshire bull terrier, Belgian Shepherd dog and Chow chow and the median age of affected dogs is 9.5 years of age. The Belgian Shepherd breed potentially has a genetic predisposition to developing gastric adenocarcinoma. The primary signs that the pet owner may see at home include vomiting, drooling, decreased activity, decreased appetite, black stools, and weight loss. Your companion's veterinarian may also detect abdominal pain, but palpation of an abdominal mass is uncommon.




The diagnosis of a stomach tumor is made upon examination of the inside of the stomach with a telescopic camera called an endoscope. A less sensitive test that may also identify a stomach tumor is an x-ray of the stomach following ingestion of barium contrast material. Confirmation of the type of tumor necessitates a biopsy, which may be done at the time of endoscopic examination of the tumor, but is frequently done after the tumor has been removed. Tests done prior to surgery may include a complete blood count, blood chemistry profile, and urinalysis to check internal organ health. Chest x-rays and abdominal ultrasound are required to rule out visible spread of the cancer.



The day of surgery

Our anesthesia and surgical team will prescribe a pain management program, both during and after surgery that will keep your companion comfortable. This will include a combination of general anesthesia, injectable analgesics, epidural analgesia, oral analgesics and anti-inflammatory medication. The surgeon will call you with an update following your companionís surgery.




Surgery is recommended to remove the tumor of the stomach. Commonly, this tumor is located in the lower part of the stomach and this portion of the stomach will need to be removed along with a small portion of the small intestine. The remaining portion of the stomach is surgically reconnected to the small intestine (Bilroth type I procedure). While in the hospital your companion will receive intravenous fluid therapy, intravenous antibiotic and sometimes anti-vomiting medication. Most patients will remain in the hospital for 2 nights following surgery.

Chemotherapy is usually recommended if the tumor is malignant. This medication will be administered every two to three weeks via intravenous injection by our oncologist for a total of four to five treatments. The treatments are typically done on an outpatient basis and may take a total of 90 minutes to complete each visit. Unlike humans, most dogs do not lose their hair and usually have only mild side effects from the medication, which may include transient loss of appetite and vomiting.




At home, you can continue to give your pet a prescribed pain reliever to minimize discomfort. Itís also extremely important to limit your dogís activity and exercise level for three weeks after surgery. The incision should be checked daily for signs of infection. An ant-acid may be prescribed for about 2 to 3 weeks after surgery to prevent formation of stomach ulcers. Two weeks after surgery, the surgeon will monitor the healing process and our oncologist will initiate chemotherapy.




Short-term complications following surgery are uncommon and may include temporary bleeding at the surgical site, infection, stomach ulcers, dehiscence (stomach incision opens) recurrence of vomiting and death. Tumor recurrence or spread of the cancer is a common sequel following surgery.

The most common tumor, gastric adenocarcinoma carries a guarded prognosis as 76% of dogs have metastasis at the time of diagnosis (in 132 cases). Overall survival times are commonly less than 6 months, however in the studies listed below the mean survival was 8.5 months (only 17 dogs had follow-up data). The median survival time following treatment of cats with gastric lymphoma with a Madison-Wisconsin chemotherapy protocol is 10 months. Dogs with a gastric leiomyosarcoma can be potentially cured with surgery alone, but the literature for the most part indicates similar survival rates as gastric adenocarcinoma. Benign tumors also can be cured with surgical excision.




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  2. Swann HM, Holt DE. Canine Gastric Adenocarcinoma and leiomyosarcoma; a retrospective study of 21 cases (1986-1999) and literature review. J Am Animal Hosp Assoc 38:157-164, 2002
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Frequently Asked Questions After Surgery

When should my dog have the first bowel movement after surgery?

  • Many dogs will not have a bowel movement for the first 4 to 5 days after surgery
  • Reasons that a dog will not have regular bowel movements after surgery include:
    • The dog has been fasted prior to surgery
    • Dogs do not eat well during the hospital stay
    • They frequently do not eat well when they go home
    • They are fed highly digestible food that produces little stool
    • Pain medication that contain narcotics (such as morphine, fentanyl patches, and tramadol) can be constipating
  • If a pet does not have a bowel movement on the 5th day of being home, a stool softener such as metamucil can be fed
    • Dose of metamucil is 1 tsp per 25 Kg mixed in with each meal (canned dog food); feed immediately after mixing, as the metamucil will gel the food and may make it less palatable

My pet had surgery and will not eat.  What can be done?

  • Dogs
    • Most pets will not eat their regular dog food after surgery, especially if it is kibble.
    • Offer a cooked diet having a 1:1 ratio of a protein source and carbohydrate source.  The protein source can be any meat (example: chicken breast, turkey breast, lean hamburger) that is low in fat and should be cooked (drain off all fat after the meat has been cooked).   The carbohydrate can be pasta, potato or white rice.
    • Try canned dog food; to enhance the flavor sprinkle a very small amount of garlic powder or chicken or beef broth (Chicken-in-a- MugTM or Beef-in-a-MugTM products)
    • Try Gerber strained meats for babies such as the chicken, beef, turkey, or veal
    • Try Hill's A/D diet available at most veterinary hospitals
    • Hand feeding: place a small amount of food in the mouth so that your dog gets the flavor
    • Warm the food slightly in a microwave, as the food will be more aromatic; stir the food before feeding and test the temperature on the bottom side of your wrist; it should only be luke warm.
    • Remember that most pets will not eat the first day or two after they get home from surgery
  • Cats
    • Offer smelly foods that contain fish such as tuna or smelly cat foods
    • Try Gerber strained meats for babies such as the chicken, beef, turkey or veal
    • Hand feeding:  with your finger place a small amount of food on the roof of your cat's mouth; use a syringe to get soft food into the mouth
    • Warm the food slightly in a microwave as the food will be more aromatic; remember to stir the food before feeding and test the temperature; it should be only luke-warm
    • Some cats will only eat dry food, try kibble if your cat normally has been fed that food
    • Petting and stroking your cat frequently will help to stimulate appetite
    • Remember that most pets will not eat the first day or two after they get home from surgery
    • Appetite stimulants such as cyproheptadine may be helpful
    • If your cat refuses to eat anything for 7 days a stomach tube or nasogastric tube should be placed to provide nutrition so that a serious liver problem (hepatic lipidosis) does not develop

My pet is vomiting.  What can be done?

  • The first thing for you to discern is whether your pet is vomiting or regurgitating.  Both will result in fluid or food being brought up.  Vomiting always will have heaving or retching of the abdomen prior to expulsion of the vomitus.  Regurgitation is not associated with heaving and the pet usually just opens the mouth and fluid or food will be expelled.  Usually the regurgited material will be clear or brown colored fluid. 
  • Next is to identify the cause of the vomiting or regurgitation.
  • Causes and treatment of vomiting after surgery
    • When some pets return home after a stay in the hospital they may drink excessive amounts of water at one time and then vomit; if this appears to be the case, the water should be limited to frequent smaller amounts.
    • Medications such as antibiotics, narcotics or nonsteroidal anti-inflammatory medication commonly cause vomiting after surgery.  In order to see which medication is causing the problem, the administration of each drug should be separated 2 hours apart.  Usually the pet will vomit or appear nauseated (drooling and sick look) within 1 hour of administration of the medication that they are sensitive to.  The antibiotic in some cases may be changed to a different one, or may be discontinued. 
    • Stomach upset from anesthesia is a potential cause of vomiting and will pass within a couple of days. 
    • An uncommon cause of vomiting after surgery is internal organ failure.  Blood testing will confirm this problem. For this reason vomiting should not be ignored if it persists for more than 24 hours.
    • If your pet had surgery of the bowels or stomach, vomiting is always a concern, as it may indicate that infection of the abdominal cavity, called peritonitis, is present.  Do not ignore this sign.
    • Symptomatic treatment of vomiting involves withholding food for 12 to 24 hours, then introducing small amounts of bland food such as rice and lean cooked hamburger, if your pet does not vomit after that then gradually wean him/her back onto the regular diet after 3 days.  In order to decrease the acidity of the stomach, Pepcid AC 0.5 mg/kg can be given by mouth twice daily for 5 days.  Metoclopramide and Cerenia are good anti-vomiting medications for dogs and cats.  You should always consult a veterinary healthcare professional before administering medication.
  • Causes and treatment of regurgitation after surgery
    • The most common cause of regurgitation is reflux of acid from the stomach into the esophagus while your pet is under anesthesia.  Acidic fluid from the stomach can cause a chemical burn of the esophagus and result in a bad case of heart burn, called esophagitis.  This results in poor motility of the esophagus, therefore water and food will accumulate in this structure.  In most cases, esphagitis is self-eliminating and will resolve within two or three days. 
    • If the esophagitis is severe the esophagus may develop one or more strictures.  A stricture is a narrowing or stenosis of the esophagus and does not allow passage of food down the esophagus, in regurgitation that lasts longer than one week.  This problem should be brought to the attention of your pet's doctor within the first two weeks so that it can be treated by ballooning the stricture (minimally invasive procedure, as it is done with the aide of an endoscope).  If an esophageal stricture is chronic surgery is needed.
    • Symptomatic treatment of regurgitation caused by esophagitis includes feeding bland food, and administering a coating agent (sucralfate) and an acid blocker (omeprazole or other).  Consult a veterinary health care professional if the regurgitation continues for more than a couple of days.

How do I know that my dog is in pain following surgery?

  • Signs of pain include
    • crying
    • biting if you get near the surgical site
    • grimacing (lips are pulled back and the the dog looks anxious)
    • tragic facial expression
    • panting
    • restlessness and unable to sleep; pacing
    • if abdominal surgery was done the pet will not lie down on the incision, or will continually sit up in spite of appearing very tired
    • the worst pain will be for the first 2 to 3 days after surgery

What can I do to control my dog's pain?

  • Narcotic medications that control pain: tramadol, butorphanol, Duragesic (fentanyl patch)
  • Anti-inflammatories used to control pain: Deramaxx, Rimadyl, Previcox, or Etogesic
  • If an orthopedic surgery has been done cold packing the surgical site may be helpful
    • A cold pack may be a pack of frozen peas, crushed ice in a Ziploc bag, or a cold gel pack; place a thin barrier between the skin and the cold pack.  An alternative to a cold pack is to freeze water in a styrofoam cup; after frozen cut the bottom of the styrofoam cup out. Cool the surgical site around the incision by rubbing the exposed ice directly on the skin in a circular pattern.  Cooling the surgical site helps to numb the area.

How do I know that my cat is in pain following surgery?

  • Pain is more difficult to assess in cats versus dogs, as signs can be more subtle and they usually do not vocalize when in pain
  • Signs of pain in a cat include the following:
    • biting if you get near the surgical site
    • growling or deep cry
    • not wanting to eat
    • hiding and not wanting to be near owner (remember that this could also be caused by the cat just being upset about leaving home and coming back)

What can be done for pain at home for my cat?

  • Pain medication such as buprenorphine or a Duragesic (fentanyl) patch
  • Tylenol will kill a cat as they lack abundant glutathione enzyme in the liver
  • Anti-inflammatories can be used, but the dose is much less than dogs

Is it okay for my pet to lick the incision?

  • If a dog licks the incision, the healing process may be delayed.
  • Licking can remove stitches and cause the incision to open
  • Licking can become a severe habit that is difficult to break
  • Licking can cause infection as the mouth has many bacteria
  • Dogs will frequently lick the incision when the owner is not watching such as at night time; if the skin looks red or excoriated the most common cause is from licking.
  • To stop your pet from licking the following can be tried:
    • Elizabethan collar can be placed on the neck; this will not help stop your pet from scratching at the region
    • Cervical collar (bite not collar) is a less awkward device and can be effective at stopping a pet from licking the surgical site
    • A tee shirt can be used to cover an incision on the chest or front part of the abdomen; gather the waist of the shirt up over the dog's back and wrap an elastic band around this part of the shirt.
    • A bandage or sock can be used to cover an incision on a limb; fasten the top of the sock to the dog's limb with tape.
    • Bitter apple can be applied around the incision; many dogs will continue to lick  after application of this topical
    • Bitter Apple and Liquid HeetTM (obtain this from a is used for sore muscles) mixed in a 2:1 ratio can be applied around the skin incision
    • Antipsychotic medication in some cases is needed

Board-certification by the American College of Veterinary Surgeons

What does it mean?

  • Four years of advanced training in surgery beyond the Doctor of Veterinary Medicine Degree

  • Experience in the development of new surgical treatments

  • Rigorous examination by the American College of Veterinary Surgeons to ensure competency in advanced surgical techniques

  • Assurance that a veterinarian is a surgical specialist

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