A 45-year-old woman presented with a 3-year history of confusion and seizures refractory to anticonvulsant therapy. A biochemical diagnosis of excess endogenous insulin production was established by a serum glucose level of 46 mg/dL, serum insulin level of 4 μIU/mL, C-peptide level of 0.9 ng/mL, proinsulin level of 19.9 pmol/L, and a negative sulfonylurea screen. Her neuroglycopenic symptoms were relieved by intravenous glucose administration. She had no history of peptic ulcer disease (serum gastrin level of <25 pg/mL), nipple discharge, or hypercalcemia (serum calcium level of 9.6 mg/dL). By preoperative transabdominal ultrasound, a 1-cm hypervascular mass was identified in the body of the posterior pancreas (Figure 1). She was taken to the operating room for enucleation of a well-circumscribed 7-mm insulinoma that was confirmed by immunohistochemical staining. No additional masses were identified intraoperatively by palpation. Her intraoperative serum glucose levels rebounded to 99 mg/dL without glucose infusion.
Transabdominal ultrasound demonstrating a 1-cm mass in the body of the posterior pancreas consistent with an islet cell tumor.
Her postoperative course was complicated by recurrent neuroglycopenic symptoms on the second postoperative day while ambulating. Repeated fasting laboratory values demonstrated a serum glucose level of 44 mg/dL, serum insulin level of 6.6 μIU/mL, C-peptide level of 0.7 ng/mL, and a negative sulfonylurea screen. Her neuroglycopenic symptoms were again relieved by intravenous glucose administration.
A. Surreptitious insulin administration
B. Incomplete enucleation of the previous insulinoma
C. A second insulinoma
D. Noninsulinoma pancreatogenous hypoglycemic syndrome (β-cell hyperplasia or nesidioblastosis)
Potter DD, Munson PD, Grant CS. Image of the Month—Quiz Case. Arch Surg. 2005;140(6):611. doi:10.1001/archsurg.140.6.611