Scanning For An Insulinoma
Finding an insulinoma
Blood tests establish whether insulin is being released inappropriately during low blood glucose. Scans then help locate the cause and assess any spread. A small insulinoma may remain hidden on initial imaging. [3]
CT scan
A dedicated pancreatic CT uses contrast and images taken at several stages, including the early arterial phase, to reveal small tumours with a rich blood supply. [1]
MRI scan
MRI provides detailed pancreatic and liver images, including diffusion weighted imaging. [2] MRCP can show the tumour’s relationship to the pancreatic duct. [1]
Endoscopic ultrasound (EUS)
EUS can detect very small insulinomas and guide tissue sampling. Results depend on the operator; tumours in the pancreatic tail can be missed. [1]
GLP-1 receptor imaging: exendin PET/CT
Gallium-68 exendin-4 targets receptors commonly found on localised insulinomas. It can reveal tumours missed by other scans. PET/MRI is another format. These scans are less reliable for insulinomas that have spread. [3]
Somatostatin receptor PET/CT
Examples include gallium-68 DOTATATE and DOTATOC. These scans are particularly useful for metastatic insulinoma. Some localised insulinomas lack sufficient receptors to show clearly. [3] ENETS also includes copper-64 receptor imaging. [1]
Fluorine-18 DOPA PET/CT
ENETS describes this as an alternative when GLP-1 receptor imaging is unavailable, although gallium-68 somatostatin receptor imaging performs better. [1]
When imaging is negative
ENETS recommends:
“GLP-1R PET/CT or calcium-stimulated sampling are advised in cases of insulinoma with negative imaging.” [1]
Selective arterial calcium stimulation with hepatic venous sampling measures insulin responses to identify the pancreatic region responsible. It does not directly image the tumour. This procedure is reserved for selected cases at expert centres. [1]
Other imaging techniques
FDG PET/CT: mainly useful for assessing higher grade or more aggressive neuroendocrine tumours. It has a different role from receptor PET scans. [2]
Octreoscan and somatostatin receptor SPECT: older receptor imaging methods; modern somatostatin receptor PET/CT generally detects disease better. [2]
Exendin SPECT/CT: another GLP-1 receptor technique, using tracers such as indium-111 exendin-4. Exendin PET/CT is more sensitive. [3]
Abdominal ultrasound: supports assessment, particularly of liver lesions and biopsy guidance. Contrast enhanced ultrasound can clarify uncertain liver findings. [2]
Intraoperative ultrasound: helps locate a tumour during surgery. Selective pancreatic angiography is an older invasive localisation method now used less frequently. [3]
Your NET team can advise which tests are appropriate and where specialist scans are available.
Sources
1. Main source: ENETS 2023 guidance, Question 5 (imaging).
Hofland J, Falconi M, Christ E, et al. European Neuroendocrine Tumor Society 2023 guidance paper for functioning pancreatic neuroendocrine tumour syndromes. Journal of Neuroendocrinology. 2023;35(8):e13318.
https://doi.org/10.1111/jne.13318
2. Supplementary ENETS imaging guidance.
Sundin A, Arnold R, Baudin E, et al. ENETS Consensus Guidelines for the Standards of Care in Neuroendocrine Tumors: Radiological, Nuclear Medicine and Hybrid Imaging. Neuroendocrinology. 2017;105(3):212–244.
https://doi.org/10.1159/000471879
3. Supplementary insulinoma review, “Localization” section and Table 1.
Hofland J, Refardt JC, Feelders RA, Christ E, de Herder WW. Approach to the Patient: Insulinoma. The Journal of Clinical Endocrinology & Metabolism. 2024;109(4):1109–1118.
https://doi.org/10.1210/clinem/dgad641
Page updated: 27 September 2026.