Page 1362 - Clinical Small Animal Internal Medicine

1300 Section 11 Oncologic Disease

risks of thrombophlebitis. Supplementation with zinc Unless a perforated ulcer is present, abdominal radio­
VetBooks.ir and fatty acids may also be indicated. Corticosteroids graphs are of limited use. Contrast may be useful in iden­
tifying areas of thickened gastric wall.
should be avoided as development of diabetes mellitus
Transabdominal ultrasonography is of limited
worsens the prognosis.
use because the tumors are typically small in size.
Prognosis Abnormalities that may be identified include a primary
pancreatic tumor, evidence of metastasis in the liver and
The prognosis for pancreatic glucagonomas is poor. regional lymph nodes and a thickened gastric wall.
Endoscopic evaluation of the upper gastrointestinal
tract may reveal esophagitis, esophageal and gastroduo­
Gastrinoma denal ulcerations, and a thickened pylorus. Biopsies may
reveal inflammation, gastric mucosal hypertrophy, and
Etiology/Pathophysiology loss of the mucosal barrier.
Gastrinomas in dogs and cats are nonislet cell pancreatic Serum gastrin concentrations are typically three times
tumors that secrete gastrin. In humans, the majority the upper normal range. However, they can be in the
arise in the duodenum and less commonly the pancreas. normal range. In cases of suspected gastrinoma with
There is only one report of a duodenal gastrinoma in normal gastrin levels, provocative testing can be used.
the dog. Intravenous secretin or calcium infusion can stimulate
Parietal cells are stimulated to release acid by gastrin, gastrin release.
acetylcholine, and histamine. The primary effect of A definitive diagnosis is obtained via biopsy. His­
hypergastrinemia is acid hypersecretion resulting in gas­ topathology and immunohistochemistry will confirm a
trointestinal ulceration. In humans, it is referred to as gastrinoma.
Zollinger–Ellison syndrome.
Therapy
Epidemiology Surgery is typically only palliative due to the high meta­
Gastrinomas are rare in dogs and cats. static rate. Surgical treatment may be limited by the small
size of the tumor making identification difficult. The
techniques used to identify the mass are similar to those
Signalment used for identification of insulinomas and include
Dogs are typically middle aged and cats are typically transabdominal and intraoperative ultrasound, magnetic
older. No breed dispositions have reported. resonance imaging, and computed tomography. Most
gastrinomas express somatostatin receptors on the cell
surface. Therefore, indium 111‐labeled octreotide nuclear
History and Clinical Signs scintigraphy has been used. Methylene blue injection has
Common clinical signs are vomiting and weight loss. been used for tumor identification in humans.
Other clinical signs may include hematemesis, diarrhea The goal of medical management is gastric acid
or melena, lethargy, and pale mucous membranes. reduction and treatment of gastroduodenal ulceration.
Prolonged elevation of circulating gastrin can cause gas­ Histamine receptor antagonists and proton pump inhibi­
tric antral hypertrophy. Perforated ulcers can result in tors are used. Proton pump inhibitors block all three gas­
shock and peritonitis. tric acid secretory pathways. Octreotide has two
beneficial effects: it suppresses tumor gastrin release and
inhibits gastrin from stimulating the parietal cells.
Diagnosis
A minimum database should be collected. Abnormalities Prognosis
are typically associated with gastrointestinal bleeding,
vomiting, and liver metastasis. Biochemical abnormali­ The prognosis is guarded to poor as approximately 76% of
ties may include anemia, hypokalemia, hypochloremia, cases have metastatic disease at the time of diagnosis. In
hypoalbuminemia, hypoproteinemia, and increases in animals that receive both surgical and medical manage­
liver enzymes and hyperbilirubinemia. ment, survival times range from one week to 18 months.