Role of endoscopic ultrasonography in the localization of insulinomas and gastrinomas.

BACKGROUND

We have previously found selective venous sampling to be the most sensitive method to localize otherwise occult functioning endocrine tumors. However, recently we have used endoscopic ultrasonography (EUS) as the initial and in some cases the only localization study in the preoperative evaluation of proven insulinomas and of selected cases of gastrinoma.

METHODS

All patients referred between April 1993 and April 1994 with a subsequently confirmed diagnosis of organic hyperinsulinism or Zollinger-Ellison syndrome (ZES) underwent EUS. Ten patients with insulinomas and six with gastrinomas were studied. Only one patient with ZES had multiple endocrine neoplasia type I. Patients with negative EUS findings had additional localization procedures including angiography and arterial stimulation tests. All but one patient underwent surgical exploration.

RESULTS

Solitary insulinomas were found in all 10 patients. EUS correctly identified and localized the insulinoma in seven (70%) of 10 patients but failed to identify two pedunculated insulinomas that were easily found at exploration. Because of an incomplete examination, a single insulinoma was not detected within the parenchyma. The EUS examination correctly excluded the pancreatic gastrinomas in five patients. The sixth patient, who had multiple endocrine neoplasia type I, had two 0.5 cm tumors in the head.

CONCLUSIONS

EUS is a sensitive and cost-effective technique for localization of insulinomas and may be the only study needed. In patients with ZES a negative pancreatic result suggests the likelihood of a duodenal or other extrapancreatic tumor.