Secular Trends in the Presentation and Management of Functioning Insulinoma at the Mayo Clinic, 1987–2007

Objective: The objective of the study was to assess changes in the presentation and diagnostic and radiological evaluation of patients with surgically confirmed insulinoma at the Mayo Clinic 1987–2007. Methods: A retrospective analysis of patients with insulinoma was conducted. Patients with prior gastric bypass were excluded. Results: A total of 237 patients [135 women (57%)] were identified. Hypoglycemia was reported solely in the fasting state in 73%, the fasting and postprandial state in 21%, and exclusively postprandially in 6%. There was a predominance of men in the postprandial symptom group. Considering the period of study by quartile, outpatient evaluation increased from 35 to 83% and successful preoperative localization improved from 74 to 100% comparing the first to the fourth quartiles. Although the rates of localization by noninvasive techniques remained static at approximately 75%, the addition of invasive modalities has resulted in successful preoperative localization in all patients in the past 10 yr. The sensitivity and specificity of the established diagnostic criteria using insulin, C-peptide, proinsulin, β-hydroxybutyrate, and glucose response to iv glucagon were greater than 90% and greater than 70%, respectively. Conclusions: Although fasting hypoglycemia is characteristic of patients with insulinoma, postprandial symptoms have been reported with increasing, albeit low, frequency. Trends in the evaluation and preoperative management include a shift to outpatient diagnostic testing, an emphasis on successful preoperative localization to avoid blind pancreatic exploration, and a validation of the diagnostic criteria for hyperinsulinemic hypoglycemia. Patients with insulinoma had exclusively postprandial symptoms with increasing albeit low frequency, a predominance of outpatient evaluation and avoidance of “blind” pancreatic exploration.