Diagnosis and management of insulinoma

Abstract

Insulinomas, the most common cause of hypoglycemia related to endogenous hyperinsulinism, occur in 1-4 people per million of the general population. Common autonomic symptoms of insulinoma include diaphroresis, tremor, and palpitations, whereas neuroglycopenenic symptoms include confusion, behavioural changes, personality changes, visual disturbances, seizure, and coma. Diagnosis of suspected cases is based on standard endocrine tests, especially the prolonged fasting test. Non-invasive imaging procedures, such as computed tomography and magnetic resonance imaging, are used when a diagnosis of insulinoma has been made to localize the source of pathological insulin secretion. Invasive modalities, such as endoscopic ultrasonography and arterial stimulation venous sampling, are highly accurate in the preoperative localization of insulinomas and have frequently been shown to be superior to non-invasive localization techniques. The range of techniques available for the localization of insulinomas means that blind resection can be avoided. Intraoperative manual palpation of the pancreas by an experienced surgeon and intraoperative ultrasonography are both sensitive methods with which to finalize the location of insulinomas. A high proportion of patients with insulinomas can be cured with surgery. In patients with malignant insulinomas, an aggressive medical approach, including extended pancreatic resection, liver resection, liver transplantation, chemoembolization, or radiofrequency ablation, is recommended to improve both survival and quality of life. In patients with unresectable or uncontrollable insulinomas, such as malignant insulinoma of the pancreas, several techniques should be considered, including administration of ocreotide and/or continuous glucose monitoring, to prevent hypoglycemic episodes and to improve quality of life.

Keywords: Continuous blood glucose monitoring; Diagnosis; Insulinoma; Management; Neuroendocrine pancreatic tumor; Pancreas.

Figure 1

Computed tomography of insulinoma of the pancreas. Typically, insulinomas (arrow) are hypervascular and, as a result, demonstrate a greater degree of enhancement than normal pancreatic parenchyma during the arterial and capillary phases of contrast bolus.

Figure 2

Magnetic resonance imaging of insulinoma of the pancreas. Insulinomas (arrows) generally demonstrate low signal intensity on T1-weighted images (A) and high signal intensity on T2-weighted images (B).

Figure 3

Endoscopic ultrasound features of insulinoma of the pancreas. The appearance of insulinomas (arrows) on endoscopic ultrasonography is quite characteristic, with most tumors homogeneously hypoechoic, rounded in shape, and with distinct margins.

Figure 4

Angiography and arterial stimulation venous sampling. Using arterial stimulation venous sampling, insulinomas (arrows) are seen as well-defined, round or oval vascular blushes that are of increased vascularity compared with the surrounding normal pancreatic parenchyma.

Figure 5

Changes in serum insulin levels. Changes in serum insulin levels plotted as a function of time after calcium injection indicate that insulin concentrations are markedly elevated only in the feeding arteries of the insulinoma. SMA: Superior mesenteric artery; GDA: Gastroduodenal artery; PHA: Proper hepatic artery; SA: Splenic artery.

Figure 6

In patients who have unresectable or uncontrollable malignant insulinomas of the pancreas, several strategies need to be considered to both control hypoglycemic episodes and improve quality of life, including administration of ocreotide and continuous glucose monitoring. RFA: Radiofrequency ablation; LN: Lymph node.