Overview of Gastrinoma in Dogs
Gastrinoma is a malignant tumor of the pancreas that secretes a hormone called gastrin that stimulates acid secretion in the stomach and in turn causes gastrointestinal ulceration. In human medicine gastrinomas are referred to as the Zollinger-Ellison syndrome.
There is no specific known cause or risk factor that is responsible for gastrinomas. This cancer is not very common in veterinary medicine and is seen more commonly in dogs than cats. Middle-aged to older dogs are most commonly affected. There does not appear to be a gender or breed predisposition.
What to Watch For
Although some dogs may have no clinical signs, some may have life threatening manifestations.
Vomiting (with or without blood)
Melena, which is black, tarry stool that contains digested blood
Pale mucus membranes
Diagnosis of Gastrinoma in Dogs
A complete blood cell count (CBC), biochemical profile and urinalysis should be performed in all cases.
Screening abdominal X-rays, although often within normal limits, may be of benefit in ruling out other disorders.
Abdominal ultrasound may identify a pancreatic mass, but it generally does not identify gastrointestinal ulceration itself.
A contrast upper gastrointestinal study may identify ulcers.
Gastroduodenal endoscopy is helpful in diagnosing gastrointestinal ulceration, although it does not always identify an underlying cause.
Gastrin levels may help to support a diagnosis of a gastrinoma.
Laparotomy and biopsy of the pancreatic mass is the only definitive way of documenting a gastrinoma.
Treatment of Gastrinoma in Dogs
Treatment of gastrinoma dogs should be directed at surgical excision of the tumor and control of excess gastric acid secretion.
In severe cases, hospitalization is warranted for intravenous fluid therapy and/or blood transfusions
If possible, treatment of choice is surgical removal of the tumor.
Large bleeding ulcers may also need to be removed surgically.
Individuals with gastrointestinal ulceration may be treated as outpatients if there are minimal signs and/or no systemic effects.
Food and water should be restricted if there is active vomiting, and an easily digestible diet with frequent small feedings should be reintroduced gradually.
Acid-blocking and stomach-coating drugs may be recommended.
Home Care and Prevention
Long term prognosis is poor because of the likelihood of malignancy with these types of tumors. Administer all medication and dietary recommendations as directed by your veterinarian. If your dog becomes weak, pale, or if he collapses or vomits blood, seek veterinary attention at once.
There is no preventative care for gastrinomas.
In-depth Information on Gastrinoma in Dogs
Gastrinomas are malignant tumors of the pancreas that often become progressively worse and result in death of the patient. These tumors secrete the hormone gastrin that stimulates stomach acid secretion and in turn, causes gastrointestinal ulceration. In human medicine gastrinomas are referred to as the Zollinger-Ellison syndrome. These tumors commonly metastasize, or spread to other organs, early in the disease process.
Gastrinomas are fairly uncommon in veterinary medicine, although have been reported in both dogs and cats. Signs can be extremely variable from patient to patient. Some patients may have no clinical signs, while others may be in immediate need of intensive support and hospitalization, to include very close monitoring and even blood transfusions.
Gastrointestinal ulceration has many other causes besides gastrinomas. It is important to realize that while some cases of ulceration are clear cut when reviewing the history, physical examination and diagnostic findings, it is sometimes more difficult to identify a gastrinoma as the primary cause.
Many diseases/disorders cause similar clinical signs to patients with gastrinomas.
The ingestion of certain drugs and medications may cause either gastrointestinal ulceration or signs similar to individuals with ulceration, including vomiting and lack of appetite.
Metabolic disorders such as kidney failure, liver disease, hypoadrenocorticism, hyperthyroidism in cats are often associated with vomiting and/or gastrointestinal ulceration and may need to be differentiated from gastrinomas.
Stress, pain, fear and/or major medical illness to include shock, low blood pressure, trauma, and major surgery can all be associated with vomiting and/or gastrointestinal ulceration.
Dietary indiscretion, or the ingestion of foreign bodies or inappropriate/excessive food items, is a common disorder seen in both cats and dogs. Vomiting, diarrhea and gastric ulceration are commonly seen.
Pancreatitis is an inflammation of the pancreas, and in certain cases, can be life-threatening. The most common clinical signs seen with pancreatitis are vomiting and inappetence. Pancreatitis is a common cause of GI ulceration.
Intestinal obstruction/blockage secondary to foreign bodies, tumors or an intussusception, which is the telescoping of one part of the bowel into itself, must be differentiated from and/or can cause GI ulceration.
Mast cell tumors are growths that occur anywhere in or on the body and secrete substances that can cause gastrointestinal ulceration.
Infiltrative diseases of the gastrointestinal tract, including inflammatory bowel disease and lymphosarcoma (a type of cancer) must be ruled out. Infiltrative diseases are microscopic diseases that penetrate and spread throughout the body.
Hemorrhagic gastroenteritis (HGE) is a syndrome seen in dogs that has no known cause. These animals often experience vomiting (with or without blood) and bloody diarrhea. HGE is most often seen in urban settings in small breed dogs.
Clotting disorders, such as thrombocytopenia (decreased platelet count) or warfarin toxicity (rat poison), may present with bloody diarrhea or vomiting.
Neurologic disorders, especially of the vestibular center that deals with balance and coordination, often causes vomiting.
Certain toxins, such as lead, can cause severe gastrointestinal signs and ulceration.
In-depth Information on Diagnosis
A diagnosis of a gastrinoma can be made more easily in some cases than in others, depending on the individual case and stage of disease. It is extremely important that your veterinarian obtain a full diagnostic work up.
A complete blood count (CBC) evaluates for the presence of infection, inflammation, and anemia, sometimes associated with gastrinoma.
A reticulocyte count should be performed on anemic animals. This will help determine if the type of anemia is consistent with gastrointestinal ulceration seen in these patients.
A biochemical profile evaluates the kidney, liver, electrolytes, total protein and blood sugar status. All of these parameters are important to establish in the patient with a gastrinoma, as abnormalities can be seen secondary to or associated with certain metabolic disorders as well.
A urinalysis helps evaluate the kidneys and hydration status of the patient. It is usually within normal limits in these patients.
Multiple fecal examinations are important to rule out gastrointestinal parasites as a cause of vomiting, diarrhea or other gastrointestinal signs.
Abdominal X-rays evaluate the abdominal organs and may help visualize the presence of a foreign body or tumor. A mass in the area of the pancreas consistent with a gastrinoma can occasionally be visualized, although more often their purpose is to rule out other disorders whose signs may mimic those with gastrinomas. X-rays generally do not evaluate for the presence of an ulcer.
Your veterinarian may recommend additional tests to insure optimal medical care. These are selected on a case-by-case basis.
A coagulogram, or clotting profile, may be recommended in cases where a clotting disorder is suspected. Patients with decreased platelets can present with bloody vomiting or diarrhea.
An ACTH stimulation test may be recommended to rule out hypoadrenocorticism (Addison’s disease), which can cause gastrointestinal ulceration. It is a combination of two blood tests that measures adrenal function. It is safe, and can usually be performed at your local veterinary hospital.
Bile acids are paired blood tests obtained before and after a meal that evaluates liver function, as certain liver diseases can predispose to gastrointestinal ulceration. The test is very safe and can be performed at your local veterinary hospital.
A blood lead level may be indicated in the patient with ulceration, especially in cases of known or suspected exposure to lead.
A gastrin level should be run on any patient with multiple or recurrent ulcers or signs of ulceration. This is a blood test that is performed only at certain laboratories; your veterinarian can draw the sample and submit it to the appropriated establishment. Elevated levels are usually seen in patients with gastrinomas.
Gastrin stimulation tests may be recommended in those individuals who have borderline gastrin levels. These are specialized blood tests taken at different times in response to substances injected into the patient’s body and need to be sent to a specialty laboratory.
An upper gastrointestinal barium (dye) series may be helpful in identifying ulcers. It may also help diagnose foreign objects or tumors that are not apparent on regular X-rays, or to confirm the location and extent of GI ulceration. A safe dye is given to the patient by mouth, and is then watched as it travels through the GI tract. It is a non-invasive test that can often be performed by your regular veterinarian, although in some cases it may necessitate transfer to a specialty hospital.
An abdominal ultrasound evaluates the abdominal organs and helps assess for the presence of a mass in the area of the pancreas. Organs, lymph nodes and other masses can be sampled with a needle or biopsy instrument with the guidance of ultrasound. This procedure is relatively safe, but it may necessitate a mild sedative. It is often recommended that a specialist perform the procedure.
A bone marrow aspirate may be recommended in some patients with anemia, to determine if it is secondary to an ulcer, or to reveal evidence of a different disease process such as a mast cell tumor that can cause an ulcer. It is a relatively noninvasive test. It allows analysis of a sample of the bone marrow, which is responsible for producing red blood cells, white blood cells and platelets. With a local anesthetic, a small needle is introduced into the core of the bone, and a small amount of marrow is withdrawn and analyzed. This test may be performed by your local veterinarian, although in some cases, it may be best to have it performed in a specialty hospital.
Gastroduodenoscopy (upper GI endoscopy) may be of benefit in the patient with GI ulceration. It may facilitate the removal of foreign bodies, help evaluate for ulcer disease, and sample tissue for the presence of inflammation or cancer, which may be the cause for the ulcer. Hospitalization is brief, and healing is generally quick and uneventful. It does, however, necessitate general anesthesia, and therefore is associated with minor risks. It is often necessary to refer the patient to a specialist, and is performed when other diagnostics are either inconclusive, support the diagnosis of a gastric foreign body or tumor, or necessitate a definitive diagnosis of ulceration.
Lastly, an exploratory laparotomy should be performed as a diagnostic and sometimes therapeutic tool in any individual that has had an extensive diagnostic and sometimes treatment course with little or no response. It is an invasive procedure, but it is necessary in some of these individuals along with a biopsy of the mass for a definitive diagnosis.
In-depth Information on Treatment
Management of gastrinomas in dogs focus on treatment of the tumor, inhibition of acid secretion, and, if necessary, control of hemorrhage. In cases of GI ulceration secondary to gastrinomas, initial symptomatic therapy might be of benefit. These treatments may reduce severity of symptoms or provide relief for your pet. However, conservative, symptomatic therapy is not a substitute for definitive treatment of gastrinomas.
Withholding food and water for several hours allows the GI tract to rest, and is important in treating the patient with GI ulceration secondary to any cause. Complete dietary restriction allows the lining of the GI tract to heal. Gradual reintroduction of small amounts of bland food should be instituted after the fast, and the pet should be maintained on a similar diet for weeks to months after the ulcer has been successfully treated.
Drugs that decrease or inhibit acid production by the stomach such as Tagamet (cimetidine), Pepcid (famotidine), Zantac (ranitidine), Cytotec (misoprostol) and Prilosec (omeprazole) encourage and expedite the resolution of GI ulcers.
Fluid and electrolyte therapy may be necessary in some patients with gastrointestinal ulceration, and is directed toward correcting dehydration, acid-base and electrolyte abnormalities. Additionally, blood transfusions may be indicated in the severely anemic patients.
Antiemetics, or drugs that stop vomiting, should be used with caution. Examples include Reglan (metoclopramide) or Thorazine (chlorpromazine). In selected cases their use may be recommended.
Gastrointestinal protectants and adsorbents are medications that protect or soothe and are felt to coat an irritated GI lining and bind “noxious” (harmful) agents. Examples include Carafate (sucralfate) and Pepto-Bismol (bismuth subsalicylate).
Ultimately, surgery may be indicated to remove the gastrinoma if it is operable and possibly to remove an area of continual hemorrhage associated with some bleeding ulcers that are not responsive to medical management.
Follow-up Care for Dogs with Gastrinoma
Optimal treatment for your dog requires a combination of home and professional veterinary care. Follow-up can be critical, especially if your dog does not rapidly improve. Administer all prescribed medication and diet as directed. Alert your veterinarian if you are experiencing problems treating your dog.
Discontinue/avoid any medication or substance that may be causing or exacerbating the ulceration.
Return to your veterinarian for reevaluation and monitoring of certain tests, specifically for anemia and changes in the biochemical profile.
Gastrinomas are malignant tumors that carry a very poor long-term prognosis.