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==Description==
==Description==
A gastrinoma is a neoplasm of pancreatic islet cells that secretes the hormone gastrin, an example of a ectopic paraneoplastic disease. The disease was first described by Zollinger and Ellison in humans in 1955 and it has since been recognised occasionally in dogs and cats.
A gastrinoma is a neoplasm of pancreatic islet cells that secretes the hormone gastrin, an example of a ectopic paraneoplastic disease. The disease was first described by Zollinger and Ellison in humans in 1955 and it has since been recognised occasionally in dogs and cats. Gastrinomas are the least common of the islet cell neoplasia, the other types being [[Glucagonoma|glucagonomas]] and [[Insulinoma|insulinomas]].
The excessive secretion of gastrin leads to hyperstimulation of gastric acid production from the parietal cells of the stomach.
The excessive secretion of gastrin leads to hypertrophy of the antral gastric mucosa and hyperstimulation of gastric acid production from the [[Stomach and Abomasum - Anatomy & Physiology|parietal cells]] of the stomach. Antral hypertrophy may result in '''gastric outflow obstruction'''. The excessive secretion of gastric acid leads to [[Gastric Ulceration - Dog|'''gastro-duodenal ulceration''']] and [[Oesophagitis|'''oesophagitis''']] due to gastro-oesophageal reflux. In severe cases of the disease, deep gastric ulcers may erode blood vessels causing '''haemorrhage''' or perforate, causing septic [[Peritonitis - Cats and Dogs|'''peritonitis''']]. Gastrinomas have often metastasised to local lymph nodes or to the liver at the time of diagnosis.
==Signalment==
Gastrinomas have only ever been reported in a very few dogs and cats and the disease is extremely rare.
==Diagnosis==
===Clinical signs===
Affected animals may show few clinical signs as the condition first develops but, in more advanced cases, the following signs may be documented:
*'''Anorexia''' and severe '''weight loss'''
*[[Control of Feeding - Anatomy & Physiology#The Vomit Reflex|'''Vomiting''']] which may contain blood if blood vessels are eroded ('''haematemesis'''). Vomiting occurs due to gastric irritation and possible gastric outflow obstruction.
*[['''Diarrhoea''']] which may show evidence of haemorrhage in the upper gastro-intestinal tract ('''melaena'''). Diarrhoea occurs due to the production of excessive volumes of gastric secretions and because gastrin reduces the ability of the intestine to absorb fluid and electrolytes. Malabsorption may occur due to small intestinal villous atrophy.
*'''Collapse''' and '''shock''' if an ulcer perforates to cause peritonitis.
*Severe haemorrhage may result in '''pallor''', '''tachycardia''', a '''haemic murmur''' and '''collapse'''
Affected animals may also show signs of [[Oesophagitis|oesophagitis]], including regurgitation and hypersalivation.
===Laboratory Tests===
====Haematology====
If haemorrhage is occurring, the '''packed cell volume''' (PCV) and blood '''haemoglobin''' concentration may be abnormally low and there may be signs of regeneration after 48-72 hours. In cases of chronic haemorrhage, the blood urea concentration may be raised and, as '''iron''' reserves are expended, a microcytic hypochromic anaemia may develop.
Areas of gastro-duodenal ulceration will be inflamed, producing a '''leucoytosis'''. This may be neutrophilic, monocytic or both depending on the stage of disease.
====Biochemistry====
Blood '''urea''' concentration may be elevated in cases of gastro-intestinal haemorrhage. Haemorrhage will lead to the loss of plasma proteins, producing a [[Hypoalbuminaemia|'''hypoalbuminaemia''']].
Repeated bouts of gastric vomiting may lead to the loss of gastric acid and intestinal fluid, producing hyponatraemia, hypokalaemia, hypochloraemia and [[Consequences of Gastric Disease - Pathology|metabolic alkalosis]].
===Diagnostic Imaging===
'''Ultrasonography''' is most useful for detection of gastro-duodenal ulceration and of metastases in the liver and local lymph nodes.
Ulceration and antral hypertrophy may also be visualised by '''endoscopy'''.
===Other Tests===
It is possible to measure the '''gastric pH''' using a pH meter placed into the stomach. The pH in affected animals will be persistently lower than that of normal animals.
In humans, Zollinger-Ellison syndrome is diagnosed by directly measuring serum gastrin concentration before or after injecting secretin or calcium, which both stimulate secretion. These tests have all been performed in animals but, given the very low prevalence of the disease, they are not widely available. Serum gastrin concentration may be elevated in many other disease conditions and a single basal measurement is sufficiently specific to make a diagnosis of gastrinoma in dogs<ref>Gabbert NH, Nachreiner RF, Holmes-Wood P, Kivela JH. '''Serum immunoreactive gastrin concentrations in the dog: basal and postprandial values measured by radioimmunoassay''' ''Am J Vet Res. 1984 Nov;45(11):2351-3.''</ref><ref>Happé RP, van der Gaag I, Lamers CB, van Toorenburg J, Rehfeld JF, Larsson LI. '''Zollinger-Ellison syndrome in three dogs.''' ''Vet Pathol. 1980 Mar;17(2):177-86.''</ref>.
===Pathology===
Post mortem examination of the pancreas of affected animals may reveal multiple variably sized neoplasms that feel firm because they have a large connective tissue mass. The tumours may be partially encapsulated and locally invasive. Metastases are commonly detected in the [[Liver - Anatomy & Physiology|liver]] or local lymph nodes.
==Treatment==
==Prognosis==
==References==
<references/>
[http://w3.vet.cornell.edu/nst/nst.asp?Fun=Image&imgID=7762 Image of pancreatic garstrinoma in a dog from Cornell Veterinary Medicine]
[http://w3.vet.cornell.edu/nst/nst.asp?Fun=Image&imgID=7762 Image of pancreatic garstrinoma in a dog from Cornell Veterinary Medicine]
Ettinger, S.J, Feldman, E.C. (2005) '''Textbook of Veterinary Internal Medicine''' (6th edition, volume 2)
[[Category:Pancreas_-_Hyperplastic_and_Neoplastic_Pathology]][[Category:Endocrine_System_-_Pathology]][[Category:Dog]][[Category:Cat]]
[[Category:Pancreas_-_Hyperplastic_and_Neoplastic_Pathology]][[Category:Endocrine_System_-_Pathology]][[Category:Dog]][[Category:Cat]]
[[Category:Neoplasia]]
[[Category:Neoplasia]]
[[Category:To_Do_-_James]]
[[Category:To_Do_-_James]]