ZOLLINGER-ELLISON SYNDROME WITH NORMAL SERUM GASTRIN LEVEL

Abstract

Introduction: Zollinger-Ellison syndrome is characterized by gastric acid hypersecretion leading to refractory/recurrent peptic ulceration due to non-beta islet cell tumor. Diagnosis of Zollinger-Ellison syndrome is made by elevated serum gastrin levels or secretin stimulation test in appropriate clinical setting. We describe a case of Zollinger-Ellison that had near normal serum gastrin levels. Diagnosis was made with endoscopic ultrasound and confirmed by octreotide receptor scintigraphy and histopathology. Case Report: 53-year-old white male with history of 40 lbs weight loss over four months and peptic stricture was referred for evaluation of abdominal pain, diarrhea and symptoms of gastroesophageal reflux despite being on omeprazole 40 mg twice daily. Abdominal exam did not show any evidence of fluid or masses. The patient underwent an esophageal gastroduodenoscopy, which showed diffuse ulceration of esophagus, erosions in the stomach, ulceration in the duodenal bulb and second part of the duodenum. Liver enzymes were elevated and a trans abdominal ultrasound showed dilated pancreatic duct. A CT scan obtained at the same time did not reveal any abnormalities. Serum gastrin level initially was 37 pg/ml and later rose to 161 pg/ml; normal (40–200 pg/ml). Patient refused secretin stimulation test because of fear of symptoms off proton pump inhibitors. An endoscopic ultrasound (EUS) was performed which showed a 25 mm × 30 mm mass in the head of the pancreas. Fine needle aspirate of that mass suggested endocrine tumor. Octerotide scan showed high uptake in the mid epigastric area consistent with gastrinoma. The patient underwent a Whipple procedure and resection of low grade neuroendocrine tumor of the pancreas which stained positive for chromogranin, synaptophysin and pancytokeratin consistent with gastrinoma. The patient was discharged home after one week stay in the hospital. Currently patient is doing well without any complaints of gastroesophageal reflux, one-month post surgery. Discussion: Our case illustrates the fact that normal serum gastrin levels do not rule out the diagnosis of Zollinger-Ellison syndrome. When clinical suspicion of Zollinger- Ellison syndrome is high additional testing i.e. secretin stimulation test (which shows a paradoxical rise in the gastrin levels) or EUS should be done to confirm or refute the diagnosis. A EUS can be very helpful in such situations by not only establishing the diagnosis but also localizing the tumor for surgery.