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Old 09-28-2012
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Arrow Gyrus Daily Questions; Internal Medicine #36

A 57-year-old man with peptic ulcer disease experi-ences transient improvement with Helicobacter pylori eradi-cation. However, 3 months later, symptoms recur despite acid-suppressing therapy. He does not take nonsteroidal anti-inflammatory agents. Stool analysis for H. pylori anti-gen is negative. Upper GI endoscopy reveals prominent gas-tric folds together with the persistent ulceration in the duodenal bulb previously detected and the beginning of a new ulceration 4 cm proximal to the initial ulcer. Fasting gastrin levels are elevated and basal acid secretion is 15 meq/h.
What is the best test to perform to make the diagnosis?

A. No additional testing is necessary.
B. Blood sampling for gastrin levels following a meal.
C. Blood sampling for gastrin levels following secretin administration.
D. Endoscopic ultrasonography of the pancreas.
E. Genetic testing for mutations in the MEN1 gene.
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Old 09-28-2012
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C. Blood sampling for gastrin levels following secretin administration.
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Old 09-29-2012
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Answer C = ZES
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Old 09-29-2012
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The answer is C.

Fasting gastrin levels can be elevated in a variety of conditions including atrophic gastritis with or without pernicious anemia, G-cell hyperplasia, and acid suppressive therapy (gastrin levels increase as a consequence of loss of negative feedback).

The diagnostic concern in a patient with persistent ulcers following optimal therapy is Zollinger-Ellison syndrome (ZES). The result is not sufficient to make a diagnosis because gastrin levels may be elevated in a variety of conditions. Elevated basal acid secretion also is consistent with ZES, but up to 12% of patients with peptic ulcer disease may have basal acid secretion as high as 15 meq/h. Thus, additional testing is necessary.
Gastrin levels may go up with a meal (>200%) but this test does not distinguish G-cell hyperfunction from ZES.

The best test in this setting is the secretin stimulation test.

An increase in gastrin levels >200 pg within 15 min of administering 2 μg/kg of secretin by intravenous bolus has a sensitivity and specificity of >90% for ZES.

Endoscopic ultrasonography is useful in locating the gastrin-secreting tumor once the positive secretin test is obtained. Genetic testing for mutations in the gene that encodes the menin protein can detect the fraction of patients with gastrinomas that are a manifestation of Multiple Endocrine Neoplasia type I (Wermer’s syndrome).

Gastrinoma is the second most common tumor in this syndrome behind parathyroid adenoma, but its peak incidence is generally in the third decade.
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