What is Gastrinoma?
Rare in dogs, gastrinomas are neuroendocrine tumors that are typically found in the pancreas. The tumors release gastrin, which is a key gastrointestinal neuropeptide that is responsible for gastric acid secretion. Smaller breed dogs are diagnosed with gastrinomas more often than larger breeds and there are a multitude of symptoms that can be expected if your dog is suffering from a gastrinoma. Treatment may involve surgery and/or doing what you can to help keep your dog more comfortable.
A gastrinoma is a malignant tumor that secretes gastrin and leads to an increase in both the production and secretion of gastric acid, causing significant gastrointestinal ulceration.
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Symptoms of Gastrinoma in Dogs
Should your dog have a gastrinoma (or more than one), he may experience the following symptoms:
- Abdominal pain, vomiting and diarrhea due to gastric and duodenal ulceration
- Reduced appetite and weight loss
- Regurgitation due to esophagitis (rare)
Many of the symptoms listed are due to the increased amount of gastrin being released leading to stomach ulcers, along with esophageal ulceration, duodenal ulceration, jejunal ulceration and GI perforation.
Dogs with gastrinomas may exhibit one or multiple tumors of different sizes in the pancreas. Tumors are firm to the touch as a result of fibrous connective tissue in the stroma.
In some cases, a dog may experience a gastrinoma, along with hypersecretion and peptic ulceration. Should your dog be experiencing all three, he will be diagnosed with Zollinger-Ellison syndrome.
Causes of Gastrinoma in Dogs
Gastrinomas are formed from ectopic amine precursor uptake decarboxylase (APUD) cells that are in the pancreas of your dog. Tumors that develop from these cells make up a group of neuroendocrine tumors, or NETs. Due to the wide distribution of cells, NETs may be found in multiple locations. Some NETs are responsible for the symptoms seen in the dog as they cause a greater than normal secretion. Other NETs are considered nonfunctional and the clinical signs experienced by the dog are due to the impact of expansion or the cancer metastasizing.
As the production and secretion of gastric acid increases as a result of the gastrinoma, over time, there will be significant ulceration (gastric and small intestinal). In some cases (when the gastrinoma is in the duodenum) the gastrinoma may lead to an obstruction of your dog’s bile duct.
Diagnosis of Gastrinoma in Dogs
It is likely that the change in your dog’s behavior will lead you to bring him to the veterinarian. Your veterinarian will ask you for information regarding the symptoms you have noticed in your dog, and when you began noticing them. After conducting a physical examination of your dog, he may look at the following options to diagnose what is ailing your dog:
- Blood analysis
- Serum analysis (greater than 278 ng/L)
- Ultrasonography which may show a mass within the pancreas of your dog
- Histopathology (looking at your dog’s tissues under a microscope)
- Immunohistochemistry (looking for antigens in the cell of a section of your dog’s tissue)
Typically diagnosis will be made through confirming the presence of a pancreatic carcinoma that produces gastrin by histopathology and immunohistochemistry. Low levels of gastric pH (less than 3) along with high levels of gastrin will point to a gastrinoma. Should your dog have experienced repeated ulcers in the stomach or intestine, the veterinarian may recommend exploratory surgery to see if there are any tumors in your dog’s pancreas.
Treatment of Gastrinoma in Dogs
Should your dog have one or more gastrinomas, your veterinarian may recommend the surgical resection of the tumor that is secreting gastrin. Unfortunately, this is not a cure because the cancer often metastasizes, with 76% of dogs having the cancer recur after successful surgery (65% in the liver, 30% in the regional lymph nodes, and 25% to spleen, peritoneum, and mesentery).
Other options your veterinarian may recommend are H2-receptor antagonists (famotidine or ranitidine) or omeprazole (a proton-pump inhibitor) either of which may help allay the symptoms that your dog is experiencing though it won’t resolve the gastrinoma.
Recovery of Gastrinoma in Dogs
Should your dog be suffering from a gastrinoma or multiple gastrinomas, you will want to discuss with your veterinarian how to best keep him comfortable. Medication given by your veterinarian will help stabilize your dog and stop his vomiting, however it will not resolve the gastrinoma. Should your dog undergo surgery to remove the tumor, you will want to follow the veterinarian’s instructions for his recovery, as well as attend recommended follow-up appointments. Even with surgery, recurrence of the tumor is likely and the mean survival time for dogs with this condition is five months. You will want to communicate with your veterinarian in regards to how often to schedule follow-up appointments.