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382.e2 Gastrinoma

Gastrinoma Client Education
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DIAGNOSIS
BASIC INFORMATION
• Basal gastric acid secretion: increased in more
than 80% of human gastrinoma patients.
Definition Diagnostic Overview In four reported dogs tested, all values
Rare malignant amine precursor uptake and The diagnosis is suspected based on the find- were low.
decarboxylation (APUD) cell tumors that ings of vomiting, anorexia, weight loss, and • Fasting serum gastrin concentration: best
secrete excessive amounts of gastrin, resulting diarrhea, or a combination of these, typically survey test in humans (increased in 98%
in gastric acid hypersecretion in a middle-aged to older dog/cat after other, of human gastrinoma patients). Result
more common causes of clinical signs are not correlates with dog and cat disease but
Synonym found. Confirmation requires documenting can also be elevated in nonfasting sample,
Zollinger-Ellison syndrome hypergastrinemia in fasted patients and histo- renal failure, gastric outflow obstruction,
pathologic and immunohistochemical evidence hypochlorhydria, pyloric stenosis, gastric
Epidemiology of gastrin secretion in excised pancreatic or dilation/volvulus, atrophic gastritis, chronic
SPECIES, AGE, SEX duodenal neoplasms. gastritis, small-intestine resection, hepatic
• Dogs: average age of 8.2 years (range, disease, drug administration (H2-blockers,
3.5-12 years); cats: average age of 10-12 Differential Diagnosis proton pump inhibitors, or glucocorticoids),
years • Refractory gastritis/gastric ulcer disease immunoproliferative enteropathy of basenji
• Female dogs and cats may be at a slightly • Inflammatory bowel disease dogs, and possibly Helicobacter spp infection.
higher risk than males. • GI tract neoplasia Discontinue antacid treatment for 7 days
• Chronic pancreatitis before obtaining endogenous fasting serum
GENETICS, BREED PREDISPOSITION • Common bile duct obstruction gastrin concentrations.
No breed predisposition is known. • Secretin stimulation test 2-4 U/kg IV, with
Initial Database samples at 0.2, 5, 10, and 20 minutes after
Clinical Presentation • CBC: regenerative anemia or microcytosis/ injection: preferred provocative test for the
HISTORY, CHIEF COMPLAINT hypochromasia due to GI bleeding; neu- diagnosis of gastrinoma in humans (gastrin
• Associated with gastrointestinal (GI) trophilia associated with GI ulceration, levels greater than 200 pg/mL are diagnostic
ulceration sometimes thrombocytosis in humans). Data regarding the procedure
○ Chronic vomiting (most common) • Serum chemistry panel and electrolytes: and its interpretation are limited for dogs
○ Anorexia or ravenous appetite hypoalbuminemia and hypoproteinemia and cats.
○ Weight loss due to protein loss through gastroduode- • Calcium stimulation test: data regarding the
○ Regurgitation nal ulcerations. Chronic vomiting may procedure and its interpretation are limited
○ Depression result in hypokalemia, hyponatremia, and for dogs and cats (not recommended, may
○ Lethargy hypochloremia. Metabolic alkalosis with be risky).
○ Diarrhea or without aciduria is consistent with a • 111 Iridium-octreotide or pentetreotide: soma-
○ Polydipsia gastric outflow obstruction, which may be tostatin analogs bind to receptors expressed
○ Obstipation found in some cases. Hepatic metastasis may on gastrinomas and have facilitated localizing
○ Hematemesis result in bilirubinemia and elevated liver metastatic lesions in one dog.
○ Melena enzymes. • Histopathologic evaluation with immunohis-
○ Pale mucous membranes • Abdominal radiographs: loss of abdominal tochemical staining or radioimmunoassay of
○ Abdominal pain detail if GI perforation has occurred; extracts from the tumor allows a definitive
• Associated with perforating ulcer and otherwise, generally unremarkable. Con- diagnosis.
peritonitis trast radiographs may reveal deep ulcers, • Electron microscopy may also be used for
○ Collapse prominent gastric rugae, or gastric outflow detecting pancreatic Langerhans D cell
○ Acute abdomen (pain) obstruction in some cases. intracytoplasmic secretory granules found
○ Shock • Three-view thoracic radiographs: usually in gastrinomas.
are within normal limits. Metastatic lesions
PHYSICAL EXAM FINDINGS usually occur late in the course of the TREATMENT
• Nonspecific findings: lethargy, depression, disease.
poor body condition • Abdominal ultrasound: thickened gastric Treatment Overview
• Pale mucous membranes wall or pylorus; evidence of metastasis to Treatment mainly includes medical therapy to
• Melena on rectal exam or apparent on rectal the liver or lymph nodes; diffuse increased control clinical signs associated with gastric acid
thermometer echogenicity of the liver with severe gallblad- hypersecretion. Surgical reduction of gastrinoma
• Palpable abdominal mass reported in one der dilation and marked dilation of the cystic and metastatic lesions is palliative.
cat duct, common bile duct, and extrahepatic
• May be unremarkable ducts Acute General Treatment
• Intravenous fluids and electrolyte therapy
Etiology and Pathophysiology Advanced or Confirmatory Testing to correct abnormalities associated with
Gastrinomas secrete excessive gastrin, result- • Endoscopy: esophagitis, gastric or duodenal vomiting
ing in gastric acid hypersecretion by stomach ulceration, hypertrophy of gastric mucosa • Control gastric hyperacidity.
wall parietal cells. Gastric mucosal hypertro- are evident on visual inspection. Rugae often ○ H2-receptor antagonists (famotidine 0.5-
phy, GI ulceration, esophagitis, and malas- appear normal; duodenal villous blunting and 1 mg/kg IV, IM, SQ, or PO q 12-24h or
similation secondary to enzyme inactivation ulceration support chronic hyperacidity but nizatidine 2.5-5 mg/kg PO q 24h); less
and bile salt precipitation follow. are not diagnostic of gastrinoma. effective than proton pump inhibitors

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