Preoperative Localization Of Insulinomas Research Articles

Structure-Activity Relationships and Pharmacokinetics of 111In-Labeled Glucagon-like Peptide-1 Receptor-Targeting Exendin-4 Derivatives Conjugated with Albumin Binder Moieties.

Insulinomas are neuroendocrine tumors that are derived from pancreatic β-cells, and they often overexpress the glucagon-like peptide-1 receptor (GLP-1R). Radiolabeled exendin-4 derivatives have been used to noninvasively detect the GLP-1R during the diagnosis and preoperative localization of insulinomas; however, their marked renal accumulation can hinder the imaging of pancreatic tail lesions. In this study, we designed and synthesized 111In-labeled exendin-4 derivatives that possessed 4-(4-substituted phenyl)-moieties as albumin binder (ALB) moieties ([111In]In-E4DA2-4), and studied their structure-activity relationships and pharmacokinetics (as well as those of [111In]In-E4DA1, which we previously reported) to determine their usefulness as radioligands for GLP-1R imaging. 111In-labeling was performed by reacting maleimide precursors with [111In]InCl3 in 2-(N-morpholino)ethanesulfonic acid buffer, and then, the products were conjugated with exendin-4-Cys40. A saturation binding assay using GLP-1R-expressing INS-1 cells was carried out to evaluate the in vitro affinity of the radioligands for the cells. In addition, the affinity of the 111In-labeled derivatives for human serum albumin (HSA) was evaluated in an HSA-binding assay. Furthermore, an in vivo biodistribution study and single-photon emission computed tomography (SPECT) imaging were performed using INS-1 tumor-bearing mice. [111In]In-E4DA1-4 were prepared at radiochemical yields of 6-17%. In the saturation binding assay, [111In]In-E4DA1-4 showed a similar affinity for the INS-1 cells, indicating that the kind of ALB moiety used had no effect on the affinity of the exendin-4 derivatives for the cells. In the HSA-binding assay, [111In]In-E4DA1-4 all bound to HSA. In the biodistribution assay, [111In]In-E4DA1-4 exhibited marked tumor accumulation and retention. In addition, they showed lower renal accumulation than previously reported exendin-4-based radioligands without ALB moieties. The pharmacokinetics of the 111In-labeled exendin-4 derivatives varied markedly according to the kind of ALB moiety used. In particular, [111In]In-E4DA2, which contained a 4-(4-bromophenyl)butyric acid derivative as an ALB moiety, showed the highest tumor accumulation. SPECT imaging with [111In]In-E4DA2 clearly visualized INS-1 tumors with no marked accumulation in normal organs. These results provide important information that will aid the design of novel exendin-4-based radioligands targeting the GLP-1R.

Insulinoma-Accurate Preoperative Localization Is the Key to Management: An Initial Experience.

Insulinoma is the commonest functioning pancreatic neuroendocrine tumor. The only curative treatment is surgical excision after preoperative localization. A retrospective analysis of nine patients (February 2017-June 2020), 2 males and 7 females, was done for clinical presentation, biochemistry, localization methods, intraoperative findings, postoperative outcome, histopathology reports, and follow-up. Techniques for localization of the tumor were pancreatic protocol triple-phase multi-detector computed tomography (MDCT), endoscopic ultrasound (EUS), Ga 68 DOTANOC PET-CT, and Ga 68 NOTA-exendin-4 PET-CT (GLP1R scan). The mean age was 38 (range 20-68) years and mean duration of symptoms 34 (range 8-120) months, and symptoms of Whipple's triad were present in all cases after a supervised 72-h fast. MDCT localized tumor in 8/9 cases. EUS before MDCT in one patient had also localized tumors. Ga 68 DOTANOC PET-CT detected tumor in 2/4 patients. In one patient, MDCT or DOTANOC PET scan could not localize tumor; GLP1R scan localized tumor accurately. Two patients had associated MEN1 syndrome. All 9 patients underwent surgical resection (four open and five laparoscopic) of tumor-enucleation (3), distal pancreatectomy with splenectomy (3), and pancreatoduodenectomy (PD) (3). The last four procedures and all three enucleations were laparoscopic. Five patients developed postoperative pancreatic fistula (POPF), only one grade B which required percutaneous drain placement. One patient, who had initial open enucleation, developed hypoglycemia after 48h; PD was performed. All patients were cured and all, except one (who died of upper GI bleed), were alive and disease-free during a mean follow-up of 26 (range 2-41) months. Preoperative localization of insulinoma is important and decides the outcome of surgery in terms of cure. MDCT can localize tumors in most patients; the last resort for localization is the GLP1R scan. Laparoscopic procedures are equally effective compared to open surgery. Considering the benign nature of the disease, enucleation is the procedure of choice.

Molecular Imaging to the Surgeons Rescue: Gallium-68 DOTA-Exendin-4 Positron Emission Tomography-Computed Tomography in Pre-operative Localization of Insulinomas.

Background:Insulinoma is an islet-cell neoplasm that secretes insulin. It is usually localized to the pancreas and is often the most common cause of endogenous hyperinsulinemic hypoglycaemia in non-diabetic adult patients. Surgical excision with a curative intent is the standard modality of treatment, and it requires precise localization of tumor tissue. Ga-68 DOTA-exendin-4 PET/CT scan is a clinically reasonable and sensitive scan for the identification of insulinoma. The aim of this prospective cohort study was to determine the overall accuracy of Ga-68 DOTA-exendin-4 PET/CT scan in the detection of insulinoma.Materials and Methods:Eight patients with fasting hyperinsulinemic hypoglycaemia with neuroglycopenic symptoms were enrolled in this study which was conducted during October 2016 to October 2017. Whole body PET/CT scan was performed on a Philips time of flight PET/CT scanner, 60 minutes after injection of Ga-68 DOTA-exendin-4 (and also Ga-68 DOTANOC). The imaging findings were compared to the histopathological diagnosis in six out of eight patients and to subsequent follow up in the remaining two patients who did not undergo surgery.Results:The sensitivity of Ga-68 DOTA-Exendin-4 PET/CT scan in insulinoma detection was found to be 75%.Conclusion:Ga-68 DOTA-Exendin-4 PET/CT scan is highly sensitive for identification and exact localization of insulinoma which can guide better surgical exploration. However, randomised controlled trials are needed to assess the accuracy of Ga-68 DOTA-Exendin PET/CT scan in localization of insulinoma.

Insulinoma- how to localize the tumor?

Background/Aim. Arterial stimulation with calcium and venous sampling (ASVS) enables us to reach the goal of avoiding that any patient with insulinoma undergoes a blind surgical exploration. Since ASVS is both a functional and morphological localization procedure, its sensitivity is not influenced by factors that are causing the insensitivity of usual anatomical and morphological procedures. Based on our own experience in preoperative localization of insulinoma, we indented to show why we believe that ASVS should be performed to all patients regardless of data collected from other preoperative localization methods. Methods. We have analyzed the accuracy of preoperative localization methods retrospectively. First anatomical and morphological procedures like transabdominal ultrasound (US), endoscopic ultrasound (EUS), computed tomography (CT) and magnetic resonance imaging (MRI) were done. Then we analyzed the data collected during a functional procedure which, at the same time, allows regionalization (ASVS). To estimate the accuracy, the results of every single method were correlated with the operative findings in all sixteen cases. Results. Prior to ASVS, fourteen patients underwent US, fifteen had CT, MRI was performed in eight patients and EUS in thirteen. Using only one of these methods enabled identification of tumors in five patients, using two methods in six patients while three and four in one patient each. For three patients, none of these methods was successful. ASVS revealed that all seen tumors were functional except three of the six visualized with two methods (US and EUS). In two of these three cases, US and EUS localized the tumors in pancreatic tail/body while ASVS accurately identified the tumors in pancreatic head. For these patients US and EUS showed false positive results. In the third of these patients EUS showed the tumor localized in pancreatic head, while US and ASVS accurately pointed to tail. This, too, was a false positive result of EUS. ASVS successfully provided regionalization data in three patients where other visualization methods failed. Operative and later histological findings confirmed the accuracy of ASVS in all sixteen patients including two patients that previously underwent distal pancreatectomy based on false positive EUS findings. Conclusion. Two patients, with accurate insulinoma regionalization in pancreatic head, obtained with ASVS, previously underwent unsuccessful distal pancreatectomy based on the false positive EUS findings. The same goes to three other patients with the false positive results obtained with other anatomical and morphological findings, as well as those three patients that had no preoperative visualization with other methods prior to ASVS. Therefore we suggest ASVS performing in each suspected insulinoma patient before the surgery, regardless of the data collected using other methods. This would enable us to test functional characteristics of visualized findings and to regionalize part of pancreas with uncontrolled insulin secretion when no suspicious changes were found.

Preoperative localization of an insulinoma: selective arterial calcium stimulation test performance

Preoperative localization of an insulinoma is recommended to improve the cure rate, but non-invasive procedures can fail to detect the tumour. The objective of the study was to assess the performance of a selective arterial calcium stimulation test in the preoperative localization of insulinomas that were not detected by conventional imaging procedures. We conducted a monocenter retrospective case review of 13 patients who had endogenous hyperinsulinism and were treated between 1994 and 2013. Patients were selected on the basis of negative or doubtful non-invasive preoperative imaging. A selective arterial calcium stimulation test was performed by pancreatic and hepatic arteriography with selective intra-arterial calcium stimulation and hepatic venous sampling in order to obtain the plasma insulin measurement. We evaluated the efficacy of the test by comparing the results with an endoscopic ultrasound. Twelve of the 13 patients underwent surgery, and the presence of an insulinoma was proven in 11 patients by pathological analysis of the tumour. An endoscopic ultrasound was consistent with surgery in 71.4 % of cases, while selective arterial calcium stimulation was consistent with surgery in 90.9 % and allowed detection of an insulinoma in two additional patients with a negative endoscopic ultrasound. One false-negative and one false-positive arterial calcium test were observed. No adverse events were recorded except transient skin flush following calcium injection in one patient. The selective arterial calcium stimulation test is a sensitive diagnostic procedure for localizing insulinomas and may be considered when non-invasive radiological imaging does not allow the detection of an occult insulinoma.

Determinants of surgical resection for pancreatic neuroendocrine tumors.

Pancreatic neuroendocrine tumors (pNETs) include functioning and non-functional tumors. Functioning tumors consist of tumors that produce a variety of hormones and their clinical effects. Therefore, determinants of resection of pNETs should be discussed for each group of tumors. Less than 10% of insulinomas are malignant, therefore more than 90% of the cases can be cured by surgical resection. Lymphadenectomy is generally not necessary in insulinoma operation. If preoperative localization of the insulinoma is completed, enucleation from the pancreatic body or tail, and distal pancreatectomy can be performed safely by laparoscopy. When preoperative localization of a sporadic insulinoma is not confirmed, surgical exploration is needed. Intraoperative localization of a tumor, intraoperative insulin sampling and frozen section are required. The crucial purpose of surgical resection is to control inappropriate insulin secretion by removing all insulinomas. Gastrinomas are usually located in the duodenum or pancreas, which secrete gastrin and cause Zollinger-Ellison syndrome (ZES). Duodenal gastrinomas are usually small, therefore they are not seen on preoperative imaging studies or endoscopic ultrasound, and can be found only at surgery if a duodenotomy is performed. In addition, lymph node metastasis is found in 40-60% of cases. Therefore, the experienced surgeons should direct operation for gastrinomas. Surgical exploration with duodenotomy should be performed at a laparotomy. Other functioning pNETs can occur in the pancreas or in other locations. Curative resection is always recommended whenever possible after optimal symptomatic control of the clinical syndrome by medical treatment. Indications for surgery depend on clinical symptom control, tumor size, location, extent, malignancy and presence of metastasis. A lot of non-functioning pNETs are found incidentally according to the quality improvement of imaging techniques. Localized, small, malignant non-functioning pNETs should be operated on aggressively, while in possibly benign tumors smaller than 2 cm the surgical risk-benefit ratio should be carefully weighted. Surgical liver resection is generally proposed in curative intent to all patients with operable metastases from G1 or G2 pNET. The benefits of surgical resection of liver metastases have been demonstrated in terms of overall survival and quality of life. Complete resection is associated with better long-term survival.

Endoscopic Ultrasonography - A Sensitive Tool in the Preoperative Localization of Insulinoma

A number of imaging modalities have been used in the preoperative localization of insulinomas. Computed tomography (CT) is the most commonly employed modality. Endoscopic ultrasound (EUS) allows the transducer to be placed in close proximity to the pancreas, thereby yielding higher quality images, which facilitates accurate localization, minimally invasive surgery, and a lower occurrence of residual tumors, all of which contribute to a better clinical outcome. We analyzed the hospital records of all adult patients (age >18 years) diagnosed with insulinoma between October 2004 and September 2010. The diagnosis was based on the clinical practice guidelines of the American Endocrine Society. We compared the sensitivities of EUS and multidetector computed tomography (MDCT) in lesion. Eighteen patients were seen over a period of 6 years, and all underwent EUS. MDCT scans were carried out in 17 patients. EUS had greater sensitivity (89%) in localizing insulinomas compared to CT (69%). In this series, the lesions that were missed on CT but picked up on EUS were smaller (<12 mm, P<.001). Lesions that were near mesenteric vessels and those located in the head of the pancreas were more likely to be missed on CT. EUS has a greater sensitivity in identifying and localizing insulinomas. As availability increases, EUS should be part of a preoperative insulinoma workup.

Educational Exhibit Abstract No. 386 - Calcium arterial stimulation venous sampling for preoperative localization of occult insulinomas

Learning Objectives (1) To review the clinical features, diagnosis, and treatment of insulinomas, (2) to discuss the indications and advantages of intra-arterial calcium-stimulated venous sampling (ASVS) vs. portal venous sampling and imaging for preoperative diagnosis of occult insulinomas, (3) to discuss the physiologic rationale of ASVS, technique, and result interpretation. Background Insulinomas cause symptomatic hypoglycemia and are the most common islet cell tumors. Surgical resection is curative. Preoperative localization of an insulinoma is a prerequisite of successful surgical resection. Cross-sectional imaging modalities unreliably detect insulinomas less than 2 cm in size. ASVS is a highly sensitive test for localizing such occult insulinomas. Administration of calcium gluconate into the arterial supply of normal beta cells causes insulin release. The insulin surge from beta cells of an insulinoma is much greater allowing for tumor localization based on site of arterial injection. In the setting of multifocal pancreatic lesions, ASVS can also be used to identify the region that is hormonally most active prior to the resection. Clinical Findings/Procedure Details ASVS is performed in a fasting state. Arteries supplying the pancreas are selected and calcium gluconate is injected. Blood samples are obtained from hepatic veins simultaneously with each injection and evaluated for insulin levels. Location of the insulinoma is determined based on increase in the hepatic venous insulin levels corresponding to the pancreatic arterial territory stimulated. We will discuss the diagnostic algorithm, illustrate the ASVS technique in detail, and interpret the test results. We will also explain the physiologic rationale of the test, angiographic findings of insulinoma and potential use of cone beam CT scan in optimizing localization and identification. Conclusion and/or Teaching Points ASVS is the most accurate method to localize occult insulinomas preoperatively. Familiarity with this technique has the potential to improve clinical outcomes after surgical resection.

Diagnosis and management of insulinoma

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.

Assessment of Contrast-Enhanced Ultrasonography in Diagnosis and Preoperative Localization of Insulinoma

Ultrasound Quarterly: June 2012 - Volume 28 - Issue 2 - p 127 doi: 10.1097/01.RUQ.0000415524.13763.12

Preoperative Tumor Studies Using MRI or CT in Patients with Clinically Suspected Insulinoma

Purpose: Insulinomas are rare tumors that originate from the islet cells of the pancreas. The aims of this study were to localize insulinomas preoperatively using CTand/or MRI in correlation with postoperative pathological results. Patients and Methods: Between December 2001 and June 2010, 27 consecutive patients with clinically suspected insulinoma were surgically treated in our university hospital. Preoperative CT (14 of 27 patients) and MRI studies (14 of 27 patients, one patient had both MRI and CT), operation reports, intraoperative ultrasonography reports, and pathological diagnoses were analyzed retrospectively. For each lesion, images were analyzed based on the presence of enhancement or the characteristics of signal intensities. Pathologic correlation was available for all the lesions. Results: The female: male ratio was 2.9, with a mean age of 47.5 years (range 12–82). Preoperative tumor localization was achieved by means of MRI and CT. A focal pancreatic lesion, which was hypointense on T1-weighted sequences, was detected on all the MR images (14 of 27 patients; 100%). These lesions were isointense (4 cases) to slightly hyperintense (10 of 14 cases) on T2-weighted sequences. In T1-weighted fat-suppressed contrast-enhanced sequences, there were two types of enhancement: homogeneously hyperintense lesions (in 10 of 14 cases) or peripherally hyper-, centrally isointense (in 4 of 14 cases). On all the CT images (14 of 27 patients), there was no detectable lesion on precontrast series; on arterial series in 13 of 14 patients (arterial series has not been done in one patient), lesions enhanced hypervascular in contrast to the rest of the pancreas with a mean enhancement of 147 HU (range 113–248) and 95 HU (range 65–141), respectively. On venous series in 13 of 14 patients (venous series has not been done in one patient), there was an enhanced lesion in contrast to the rest of the pancreas with a mean enhancement of 110 HU (range 91–151) and 86 HU (range 65–137), respectively. Intraoperative ultrasonography was performed in 11 of 27 patients to localize the tumor, which correlated with the results of the mentioned preoperative studies. Tumor size ranged from 9 × 11 to 31 × 37 mm. Enucleation was carried out in 14 patients, Whipple in 5, segmental resection in 3 and left distal pancreatectomy in 5 patients. The mortality rate was 0. Pathological findings were insulinoma or neuroendocrine tumors in 26 of 27 cases. One patient had a pathological finding of chronic pancreatic disease with intraepithelial neoplasia (grade 1A). Conclusion: We conclude that the preoperative localization of insulinoma in clinically suspected patients can be made on the basis of MRI and/or CT studies. A hallmark lesion is hypointense in T1-weighted sequences, homogeneously or peripherally hyperintense in T1-weighted fat-suppressed contrast-enhanced sequence using MRI (100% of cases) or/and a hypervascular enhanced lesion on arterial (100% of CT studies) and on venous series using CT (66.7% of CT studies).

Assessment of contrast-enhanced ultrasonography in diagnosis and preoperative localization of insulinoma

This study was to evaluate the value of contrast-enhanced ultrasonography (CEUS) in the diagnosis and preoperative localization of insulinoma and explore the enhancement patterns of the tumors. Unenhanced and contrast-enhanced ultrasonographic examinations of 31 patients who underwent resection of insulinomas were retrospectively reviewed. The diagnosis sensitivity and localization specificity of CEUS for insulinomas were determined. Results of unenhanced ultrasonography and CEUS were compared by Chi-square test. Unenhanced ultrasonography could display 9 of 37 (24.3%) surgically verified insulinomas in 31 patients, while the diagnosis sensitivity and localization specificity of preoperative CEUS was 33 (89.2%) and 32 (86.5%) of the 37 tumors, respectively. In contrast to the unenhanced ultrasonography, the improvement of CEUS in the diagnosis and preoperative localization of insulinomas was significant (p<0.0001). The enhancement pattern of insulinoma on CEUS was fast wash-in and slow wash-out. All the tumors were homogeneous hypervascularity in the earlier arterial phase, while the tumors still displayed hyperenhancing pattern in the late phase. Our study demonstrates the great potential of CEUS in the diagnosis and preoperative localization of insulinomas. Since CEUS is a convenient, inexpensive, effective and non-invasive modality, the study supports the use of CEUS as a primary tool in the evaluation of patients with insulinomas.

Preoperative detection of insulinomas: two case reports

BackgroundInsulinoma is the most common endocrine tumor of the pancreas. Accurate preoperative detection and localization of insulinomas is essential for the appropriate selection of candidates for surgery. We present two cases with benign pancreatic insulinoma.Case presentationPreoperative evaluation for patients with suspected insulinomas has been controversial. Endoscopic ultrasonography (EUS) has a sensitivity of 95% in well skilled operators and well tolerated preoperative imaging method.ConclusionWe have detected the insulinomas with EUS before surgery in our patients but other imaging modalities did not help us for localization of them. Patients have been asymptomatic postoperatively with no hypoglycemia on repeat fasting. We reviewed here the different modalities for preoperative localization of insulinoma.

Preoperative localization of pancreatic insulinoma by super selective arterial stimulation with venous sampling

Although most insulinomas are small, they have been successfully detected by computed tomography and magnetic resonance imaging recently. However, preoperative localization of the insulinomas by arterial stimulation with venous sampling is crucial when they show atypical findings on these imaging modalities. We report a case of a large benign insulinoma located at the pancreatic tail; this tumor was diagnosed correctly by super selective arterial stimulation with venous sampling.

Role of EUS in Pre-operative Localization of Insulinomas

Introduction: Insulinoma is an uncommon pancreatic neuro-endocrine tumour characterized by hyperinsulinemic hypoglycemia. It is important to surgically remove this tumor as it can cause potentially lethal hypoglycemia. The conventional imaging techniques have limitations in accurate pre-operative localization of small duodeno-pancreatic neuroendocrine tumors. The high spatial resolution of endoscopic ultrasound (EUS) permits better detection of such small tumors. We describe a report of 12 patients supporting the above observation. Results: 12 patients with insulinoma who had surgery at our institution were reviewed. (7 enucleation, 3 distal pancreatectomy, 2 unresectable). One of the patient with unresectable tumor was locally invasive and other had vascular invasion not detected on EUS prior to surgery. 9 of the tumors were located in the tail, 2 in head of pancreas and 2 in the body of pancreas (one patient had two tumors). The mean size of tumors was 2.72×2.18cm. Three patients had surgical resection done before EUS was available at our center. Pre-operative CT scan failed to localize the tumor in these patients. EUS done in the other nine patients accurately localized the tumor prior to surgical resection. Immunological staining on fine needle aspiration obtained at the time of EUS was consistent with insulinoma and revealed malignancy in one patient. One patient had two tumors which were detected on EUS prior to surgery. Conclusion: Our experience with 12 patients is in accordance with previous reports claiming EUS to be the method of choice for preoperative imaging and localization of pancreatic islet cell tumors. Preoperative evaluation is necessary for planning pancreatic surgery to assess for resectability

Preoperative localization of insulinoma by intra-arterial spiral CT

Objective To evaluate the value of intra-arterial dynamic spiral CT on preoperative localization of insulinoma.

Role of EUS in the preoperative localization of insulinomas compared with spiral CT

Role of EUS in the preoperative localization of insulinomas compared with spiral CT

Preoperative localization of insulinomas is not necessary

Background: Insulinomas are infrequent but are important to recognize and surgically remove. Several diagnostic tests have been used to increase the chances of operative success. The value of preoperative testing for insulinomas is the subject of this review.Study Design: All patients treated at the Cleveland Clinic for insulinoma between 1985 and 1995 were retrospectively reviewed. All patients had biochemical evidence of primary hyperinsulinemia.Results: There were 21 patients, 10 men and 11 women, with a median age of 58 years. Eighteen patients (85%) had a single insulinoma, two patients (10%) had multiple insulinomas, and one patient (5%) had nesidioblastosis. In addition, two patients (10%) had malignant insulinoma. A total of 13 patients (62%) had successful preoperative localization of their tumors, and all of these were found during exploration either by the surgeon (12 patients) or by intraoperative ultrasonography (1 patient). The remaining eight patients (38%) did not have their lesion localized by preoperative tests. In seven patients these tumors were found at operation, three by the surgeon and four by intraoperative ultrasonography. One patient failed preoperative and intraoperative localization and was later diagnosed with nesidioblastosis. Enucleation was performed in 13 patients and distal pancreatectomy in 7; the patient with nesidioblastosis had a negative laparotomy and a subsequent distal pancreatectomy. The mortality and morbidity rates were 0% and 14%, respectively. Only two patients, including the patient with nesidioblastosis, remained symptomatic after operation.Conclusions: The diagnosis of an insulinoma does not require extensive localization studies before operation. The combination of surgical exploration and intraoperative ultrasonography identified more than 90% of insulinomas. When technically feasible, enucleation is curative and can be accomplished with low morbidity.

Endoscopic ultrasonography and somatostatin receptor scintigraphy in the preoperative localization of insulinomas and gastrinomas : Zimmer T, Stölzel U, Bäder M, et al. (B. Wiedenmann: Abteilung Gastroenterologie, Klinikum Benjamin Franklin, Freie Universität Berlin, Hindenburgdam 30, D-12200 Berlin, Germany). Gut 1996;39:562–568

Endoscopic ultrasonography and somatostatin receptor scintigraphy in the preoperative localization of insulinomas and gastrinomas : Zimmer T, Stölzel U, Bäder M, et al. (B. Wiedenmann: Abteilung Gastroenterologie, Klinikum Benjamin Franklin, Freie Universität Berlin, Hindenburgdam 30, D-12200 Berlin, Germany). Gut 1996;39:562–568

Value of tumor localization in patients with insulinoma

Based on our patient material, preoperative localization of insulinoma was correct with sonography in 13 (61.9%) of 21 patients, with computed tomography in 3 (21.4%) of 14 patients, with computed tomography with bolus injection of contrast medium in 11 (73.3%) of 15 patients, with angiography in 20 (66.6%) of 30 patients, and with percutaneous transhepatic portal vein catheterization with selective measurement of insulin in 10 (76.9%) of 13 patients. Intraoperatively, 40 (95.2%) of 42 insulinomas were palpable and 12 of 16 insulinomas were identified during intraoperative sonography. Although 95.2% of the insulinomas can be palpated, we would support additional diagnostic localization since it may improve the reliability of palpation.