Insulinoma- Invasive preoperative localisation may not be necessary in all patients?

R Kadiyala; Nicola Strickland, James Jackson, Adil Al-Nahhas JF Todd. Imperial Centre For Endocrinology, Imperial College Healthcare NHS Trust, Hammersmith Hospital.

A 67 year old man was initially referred to us in 2009 with more than 10-15 year history of profuse sweating, lightheadedness and tremor particularly in the post prandial period. He felt like his ‘batteries had run down’. His symptoms mostly occurred 4-5 hours after lunch and also on exercise but never in the morning. Food terminated these episodes. His weight was stable, having gained 3 pounds over 3 years. He was a former airline pilot but currently a driving instructor and he felt his symptoms did not have any impact on his work life. He was an ex smoker and drank a maximum of 7 pints of traditional ale per week.  His 5 hour OGTT revealed reactive hypoglycaemia and during a 72 hour fast, at 27 hours his blood sugar was 2.1 mmol/L with insulin of 3.5 iu/l and a C-peptide of 312 pmol/l. Blood ketones were suppressed at 0.8 and Suphonylurea screen was negative. These results were consistent with an insulinoma.

Localization studies included  a CT scan of the upper abdomen with pancreatic protocol did show a 15-mm well-circumscribed hypervascular lesion in the uncinate process of the head of the pancreas adjacent to the mesenteric vein compatible with a neuroendocrine tumour/insulinoma. This has also been confirmed on MRI scan. The gallium 68 DOTATATE PET scan was also strongly positive in the same area consistent with an insulinoma.


These tests were consistent with an adequately localised insulinoma and therefore  it was decided not  to  proceed to selective arterial stimulation with hepatic venous sampling or an EUS. He underwent laparoscopic resection of Insulinoma in September 2010. Histology confirmed a well differentiated endocrine tumour (insulinoma), diffusely expressing insulin and also positive for chromogranin and synaptophysin. Ki-67 index was 2%.He was well postoperatively with no symptoms was keen to restart flying. A repeat 3 day fast in August 2011 was normal.

Conclusion: Fasting hypoglycaemia is a hallmark of Insulinoma, however patients can also present with reactive hypoglycaemia. Accurate localisation preoperatively is essential and can be achieved with non-invasive investigations as demonstrated in our case. However invasive selective arterial stimulation with venous sampling may still be required in patients with negative and /or discordant cross-sectional and functional imaging and in patients requiring reoperation.