gastrointestinal disorders
Gastrinoma
Diagnosis of Gastrinoma
Serum gastrin level CT, scintigraphy, or positron emission tomography (PET) to localize Gastrinoma is suspected by history, particularly when symptoms are refractory to standard acid suppressant therapy. Serum gastrin levelis the most reliable test. All patients have levels>150 pg/mL (> 72 pmol/L); markedly elevated levels of>1000 pg/mL (> 480 pmol/L) in a patient with compatible clinical features and gastric acid hypersecretion of>15 mEq/hour establish the diagnosis. However, moderate hypergastrinemia can occur with hypochlorhydric states (eg, pernicious anemia, chronic gastritis, use of proton pump inhibitors), in renal insufficiency with decreased clearance of gastrins, in massive intestinal resection, and in pheochromocytoma. 2 mcg/kg is given with serial measurements of serum gastrin (10 minutes and 1 minute before, and 2, 5, 10, 15, 20, and 30 minutes after injection). The characteristic response in gastrinoma is a paradoxical increase in gastrin levels, the opposite of what occurs in patients with antral G-cell hyperplasia or typical peptic ulcer disease. Patients also should be evaluated for Diagnosis , which commonly results in peptic ulceration and moderate excess gastrin secretion. Once the diagnosis of gastrinoma has been established, the tumor or tumors must be localized. The first test is abdominal CT or somatostatin receptor scintigraphy, which may identify the primary tumor and metastatic disease. PET or selective arteriography with magnification and subtraction is also helpful. If no signs of metastases are present and the location of the primary tumor is uncertain, endoscopic ultrasonography should be done. Selective arterialsecretininjection is an alternative. 