During an outpatient evaluation, a -year-old male describes a one-year history of chronic watery diarrhea and burning epigastric pain that routinely awakens him from sleep. He has a history of multiple hospitalizations for complicated duodenal ulcers despite strict adherence to daily high-dose pantoprazole. Recent upper endoscopy revealed prominent hypertrophic gastric folds and multiple ulcerations extending into the distal duodenum and proximal jejunum. Histopathology from gastric biopsies was negative for *Helicobacter pylori* organisms. The clinician highly suspects an underlying neuroendocrine etiology.
Arrange the following diagnostic and therapeutic steps in the most appropriate chronological sequence for the evaluation and management of this patient's suspected condition.
- 1Cessation of ongoing proton pump inhibitor therapy
- 2Assessment of fasting serum gastrin concentration and gastric pH
- 3Confirmatory biochemical evaluation via secretin stimulation testing
- 4Anatomic localization of the primary lesion using functional imaging
- 5Curative surgical resection of the identified neuroendocrine tumor