A 34-year-old woman has recurrent episodes of sweating, palpitations, tremor, and confusion relieved promptly by eating. During a supervised 72-hour fast she develops biochemically confirmed hypoglycemia with inappropriately high serum insulin and detectable C-peptide. Which investigation provides the best localisation of the presumed lesion?

• A Contrast-enhanced CT abdomen
• B Octreotide scintigraphy
• C Selective arterial calcium stimulation with hepatic venous sampling
• D Endoscopic ultrasonography ✓

Explanation

Insulinomas are typically small, solitary, intrapancreatic and benign, making them hard to see on conventional cross-sectional imaging. Endoscopic ultrasound detects over 90 percent of insulinomas because of its high resolution and is the first-line localisation test. Octreotide scintigraphy is unreliable since many insulinomas lack somatostatin receptor subtype 2. Selective arterial calcium stimulation is reserved for lesions missed by other modalities, and CT alone misses a substantial proportion of subcentimetre tumours.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.