Imaging and localization of pancreatic insulinomas A. Chatziioannou a, *, D. Kehagias a , D. Mourikis a , A. Antoniou a , G. Limouris a , A. Kaponis b , N. Kavatzas c , S. Tseleni c , L. Vlachos a a Department of Radiology, Areteion Hospital, University of Athens, 76, Vas. Sofias Street, Athens 11528, Greece b Department of Surgery, Athens Medical Center, Athens, Greece c Department of Pathology, University of Athens, Athens, Greece Received 15 January 2001; accepted 28 February 2001 Abstract For pancreatic insulinomas, the treatment of choice is surgical excision, which when successful is curative. Intraoperative palpation combined with ultrasonography theoretically depict almost all tumors, however the accuracy of palpation is improved by preoperative localization. All recent advances in imaging have improved the likely hood for curative surgical resection. Our purpose is to demonstrate the characteristics of all modalities, which may be used in the preoperative localization algorithm. D 2001 Elsevier Science Inc. All rights reserved. Keywords: Pancreatic; Insulinomas; Imaging; Localization 1. Introduction Insulinomas are the most frequent functioning islet cell tumors [1]. There is a 2:1 female predominance, occurring in the fifth and sixth decades of life. About 10% are multiple, 10% are malignant and 4% are associated with multiple endocrine neoplasia type 1 [2,3]. The clinical pre- sentation is the Whipple triad (symptoms of hypoglycaemia, low blood glucose levels and symptomatic relief with glucose administration). The tumors are often small; 90% are < 2 cm in diameter. Preoperative localization is very important with significant reduction of the operative time. Despite the availability of all state-of-the-art imaging techniques, the localization of these tumors remains a challenge for the radiologist. Ultrasound (US), computed tomography (CT), magnetic resonance imag- ing (MRI), arteriography, intraarterial stimulation with venous sampling (ASVS), somatostatin receptor scintigraphy (SRS) and endoscopic (EUS) and intraoperative US (IOUS) are all available for the investigation of insulinomas, with variable success. The purpose of this paper is to demonstrate the imaging characteristics, the sensitivity and the role of all the variable techniques in the diagnostic algorithm of these unique tumors. 2. Ultrasound The sensitivity of US ranged from 9% to 63% [4–9] in most published series and the main problems for this low visualization rate are the small tumor size, the overlying bowel gas and obesity. Visualization of tumors located in the pancreatic tail is more difficult due to overlying bowel gas. Patients with hyperinsulinism are often obese, because they eat excessive amounts of food in order to alleviate symp- toms. Recently, Angeli et al. [10] reported a sensitivity of 79.3% mainly due to quality improvement of sonographic equipment and the expertise of the radiologists. Insulinomas typically present as hypoechoic, homogeneous, well-demar- cated nodules sometimes surrounded by a hyperechoic rim. 3. Computed tomography The sensitivity of conventional CT is disappointingly low, with a range of 16–72% [4–11]. Helical CT improved the detection rate of insulinomas [12–14]. Van Hoe et al. [12] 0899-7071/01/$ – see front matter D 2001 Elsevier Science Inc. All rights reserved. PII:S0899-7071(01)00290-X * Corresponding author. Tel.: +30-1-7286310; fax: +30-1-7220253. Journal of Clinical Imaging 25 (2001) 275 – 283