What is Gastrinoma?
Endocrine cells in the pancreas revert to producing gastrin, which is the hormone that stimulates the production of the digestive acids in the stomach and intestines. This illness is also called “Zollinger-Ellison syndrome.”
A gastrinoma in a cat is a malignant tumor in its pancreas. This form of cancer is rare, showing up mainly in older, female cats. Even though this form of tumor begins in the islet cells of the pancreas, it won’t interfere with the cat’s ability to produce or use insulin. One set of the islet cells produce hydrochloric acid, which goes into the intestine to begin the digestion process. Because of this, the tumor will cause the cat’s body to produce too many digestive juices, which will affect the stomach, pancreas, small intestine and duodenum. The excess hydrochloric acid eventually causes the stomach’s lining to thicken.
Symptoms of Gastrinoma in Cats
When a cat begins to develop a cancerous tumor of its islet cells, it begins to show several symptoms:
- Chronic vomiting
- Lack of interest in food
- Weight loss
- Diarrhea (may be bloody)
- Increased thirst and urination
- Melena (a dark, tarry feces)
- Vomiting blood
- Hematochezia (passing fresh blood through the anus)
- Severe constipation
Causes of Gastrinoma in Cats
Because gastrinomas are so rare, their cause isn’t well understood. Normal pancreatic islet cell types include four cell types, each of which produce their own unique hormone. The A cells produce glucagon; B cells release insulin; D cells release somatostatin; F cells secrete pancreatic polypeptide.
Before the cat is born, its D cells produce gastrin. After the kitten is born, that changes to somatostatin, but at some point of the cat’s life, those cells revert to producing gastrin, which may lead to the development of gastrinoma. This development needs more study.
Diagnosis of Gastrinoma in Cats
After conducting a full physical on the cat, the vet will conduct blood work (CBC), which may reveal that the cat is anemic from blood loss. The good testing may also reveal a low albumin, potassium and chloride. The cat’s blood sugar and gastrin levels will be too high.
Conducting more tests, the vet will insert a small endoscope into the anesthetized cat’s mouth and down its esophagus so they can examine the cat’s stomach and intestines. This test may show the vet that a mass is present in the pancreas. The only definitive way the vet can accurately diagnose a gastrinoma is by cutting a small part of the tumor off and sending it to pathology for a biopsy. Other helpful tests include ultrasound.
The vet should also run a serum gastrin level. If these levels are high, this, along with the presence of a mass on the islet cells and a positive biopsy result let the vet know just what is wrong with the cat.
Treatment of Gastrinoma in Cats
If the vet finds that a gastrinoma can be removed, the cat will undergo surgery. During this operation, the cancerous tumor, along with any other tumors will be removed. During surgery, the vet will explore the cat’s abdomen, focusing mostly on its pancreas to look for where the tumor originated. They will also examine the lymph nodes, liver, spleen, GI system, omentum and mesentery for signs of ulcers and additional cancerous cells.
If the vet can find where in the pancreas the tumor originated, they will remove that part of the cat’s pancreas.
After the cat has recovered from surgery, the vet prescribes oral proton pump inhibitors such as omeprazole, to slow down the secretion of gastric acids into the cat’s stomach and intestines. This particular medication has been found to give cats with gastrinoma a longer survival time if they have been diagnosed with metastatic gastrinoma. Cats with this form of cancer are generally not treated with chemotherapy or radiation therapy.
Recovery of Gastrinoma in Cats
This particular cancer is considered one of the more serious types. Vets generally provide a guarded prognosis for cats given this diagnosis. Once they have communicated this to the cat’s owner, they stress keeping the cat as comfortable and relaxed as possible at home.
The cat will need pain medications to control its pain. This should be given as prescribed, with the cat’s owner not waiting until the cat indicates it is in pain to give a dosage to the cat. To prevent gastroduodenal ulcers resulting from NSAID pain medications, the cat may take misoprostol to prevent ulcers from developing.
The cat may also have to take somatostatin analogues, which slow the secretion of gastrin and hydrochloric acid. Another medication, called sucralfate, helps with the production of stomach mucus. It also repopulates epithelial cells, helps with the synthesis of prostaglandin and works to neutralize bile acids.
The cat will need a high-quality, high-nutrition cat food. The vet may prescribe a special cat cancer diet, which provides a higher level of nutrients than regular cat foods. If the cat has problems eating or digesting its food, the vet should be told.
If the cat begins to experience changes in its elimination patterns, such as having new blood in its stool, or if it begins to vomit again, it should be taken to the vet immediately.
The cat may never regain its normal level of energy after developing this type of cancer, depending on when it was diagnosed with gastrinoma. The cat’s owner should consult closely with the vet to determine whether treatment will add to the cat’s quality of life or not. If not, the pet owner and vet need to discuss the next step.