Value of abdominal sonography and MR imaging at 0.5 T in preoperative detection of pancreatic insulinoma: a comparison with dynamic CT and angiography

Diagnostic value of ASVS for insulinoma localization: A systematic review and meta-analysis

BACKGROUND

Previous studies on the diagnostic value of arterial calcium stimulation with hepatic venous sampling (ASVS) for the localization of insulinoma have reported inconsistent results. Here, we performed a meta-analysis of the relevant published studies.

METHODS

PubMed, Embase, Web of Science, the Cochrane Library, and Wanfang Data were searched for studies on the diagnostic value of ASVS in insulinoma localization published up to May 2019. We calculated the sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR), and receiver operating characteristic (ROC) curve of ASVS in the localization of insulinoma.

RESULTS

We included ten studies involving 337 patients in the study. The pooled sensitivity, specificity, PLR, and NLR were 0.93 (95% confidence interval [CI]: 0.83-0.97), 0.86 (95%CI: 0.75-0.93), 6.8(95%CI: 3.7-12.7), and 0.08 (95%CI: 0.03-0.19), respectively. The DOR was 84 (95%CI: 30-233), and the area under the ROC curve was 0.96 (95%CI: 0.94-0.97).The results of the heterogeneity of the studies (P = 0.00, I2 = 80.17) were calculated using forest plots of the DOR.

CONCLUSION

ASVS is of significant value in localization of insulinoma. If a qualitative diagnosis of insulinoma is definite and the imaging examination results are negative, ASVS should be performed to confirm the localization of insulinoma.

Cross sectional and nuclear medicine imaging of pancreatic insulinomas

Insulinomas are rare neuroendocrine tumors which occur predominantly in the pancreas. Although majority of the insulinomas are benign, over-secretion of insulin by the tumor leads to debilitating hypoglycemic symptoms. The diagnosis is based on clinical and biochemical findings. After the diagnosis is made, the principal challenge lies in locating the tumor because most tumors are solitary and small in size. Locating the tumor is of paramount importance as complete surgical excision is the only curative treatment, and incomplete resection leads to persistence of symptoms. Different preoperative and intraoperative imaging techniques have been used with varying success rates for the insulinoma imaging. Besides localizing the tumor, imaging also helps to guide biopsy, detect metastatic lesions, and perform image-guided therapeutic procedures. This review will discuss the role of different Cross sectional and nuclear medicine imaging modalities in insulinomas.

Multiple Endocrine Neoplasia Syndromes: A Comprehensive Imaging Review

MEN1, MEN2, and MEN4 comprise a series of familial disorders involving the simultaneous occurrence of tumors in more than one endocrine organ, collectively known as multiple endocrine neoplasia. Patients with this family of disorders develop tumors of the parathyroid gland, pancreas, pituitary gland, adrenal gland, and thyroid gland, along with miscellaneous neuroendocrine tumors of the respiratory and gastrointestinal tracts. Although some patients undergo early prophylactic surgical management, particularly in the setting of familial medullary thyroid carcinoma, many develop tumors later in life. These tumors are often discovered at imaging for screening purposes. Recognition of the imaging features of the known tumors is important for appropriate patient management.

Gastroenteropancreatic neuroendocrine tumours (GEP-NET) - Imaging and staging

Detection of gastroenteropancreatic neuroendocrine tumours (GEP-NETs) and monitoring of treatment response relies mainly on morphological imaging such as computed tomography (CT) and magnetic resonance imaging (MRI). Molecular imaging techniques also in combination with CT (hybrid imaging) greatly benefit patient management, including better localization of occult tumours and better staging. Somatostatin receptor scintigraphy (SRS) and somatostatin receptor (SSTR) positron emission tomography (PET) play a central role in the diagnostic work-up of patients with well-differentiated GEP-NETs. SSTR PET/CT is superior to SRS and should be used whenever available. (18)F-DOPA and (18)F-FDG PET/CT is inferior to SSTR PET/CT at least in patients with well-differentiated GEP-NETs. Both SSTR PET/CT and SRS have limitations, such as relatively low detection rate of benign insulinomas, poorly differentiated GEP-NETs and liver metastases. New innovations such as SSTR PET/MRI, radiolabelled SSTR antagonists and glucagon-like peptide-1 receptor (GLP-1R) agonists might further improve imaging of GEP-NETs.

Pancreatic neuroendocrine tumors

Pancreatic neuroendocrine tumors (pancreatic NETs) are rare, low- to intermediate-grade neoplasms thought to arise from the pancreatic islets. Recent advances in pathology and our understanding of the biological behavior of this group of tumors has resulted in changes in their nomenclature and how we treat them. This review puts into perspective our current understanding of pancreatic NETs in terms of their incidence, pathology, and management.

Tailored imaging of islet cell tumors of the pancreas amidst increasing options

Pancreatic islet cell tumors are neuroendocrine tumors, which can produce hormones and can arise as part of multiple endocrine neoplasia type 1 or von-Hippel-Lindau-disease, two genetically well-defined hereditary cancer syndromes. Currently, technical innovation improves conventional and specific molecular imaging techniques. To organize the heterogeneous results described for the imaging of these tumors, we distinguished three indications (1) imaging of a patient with hormone hypersecretion, (2) search for a pancreatic primary in case of proven neuroendocrine cancer of unknown primary, and (3) screening of asymptomatic mutation carriers. We searched for publications on imaging of islet cell tumors between 1995 and January 2010 and defined a Level of Evidence (LOE) for the applicability of each technique. For each technique, data were analyzed in a Forest plot and arranged per imaging indication and tumor subtype. LOEs are weak for all imaging techniques. Analyses indicate a prominent role for endoscopic ultrasound for all three indications.

Vascular involvement in periampullary tumors: MDCT, EUS, and CDU

In patients affected by periampullary tumors, surgical resection represents the only treatment with curative intent. Preoperative evaluation of vascular involvement is necessary to avoid surgical treatments unable of curative intent resection. The aim of our update article is to assess the performance of multidetector computed tomography (MDCT), endoscopic ultrasonography (EUS), and color Doppler ultrasonography (CDU) in the evaluation of vascular involvement of major peripancreatic vessels, in periampullary tumors, analyzing the current and past literature.

Ultrasonography of the pancreas. 1. Conventional imaging

Ultrasound imaging has made significant advances in recent years and plays an important role in the detection, characterization and staging of pancreatic diseases. Conventional ultrasonography (US) is a noninvasive imaging modality, which continues to be the first diagnostic step in the evaluation of the pancreas. Over its various decades of application, US have detected pancreatic pathology of great diversity. This article reviews the wide utility of US and the many examinations techniques, such as filling the stomach with water, changing the patient's position or suspending inspiration or expiration, allowing us to visualize all portions of the pancreas in a high percentage of patients.

Surgical approach to insulinomas: are pre-operative localisation tests necessary?

INTRODUCTION

Insulinoma is a rare, but curable, endocrine tumour. The ability to localise the tumour accurately before or during surgery is an important factor in the management of these elusive lesions, which has been extensively debated. We have reviewed our experience of these lesions to establish the role of localisation tests.

PATIENTS AND METHODS

The medical records of 20 consecutive patients who had surgery for sporadic insulinomas since 1985 at this institution were retrospectively reviewed. All the patients had a definite biochemical diagnosis of endogenous hyperinsulinism. Results of pre-operative and intra-operative localisation tests were compared with the final outcome.

RESULTS

Of the 20 patients with sporadic insulinomas reviewed, 17 patients (85%) had multiple pre-operative localising investigations. Overall accuracy of pre-operative localisation tests was 33%. Non-invasive pre-operative localisation tests (ultra-sonography, CT, MRI) had a combined localisation rate of 25% with MRI having the highest sensitivity of 71%. Invasive tests (angiography, transhepatic portal venous sampling [THPVS], endoscopic ultrasound) detected 48% of lesions with THPVS being most sensitive (67%). THPVS was particularly helpful in localising lesions before re-operation. Intra-operative inspection and palpation localised the lesions correctly in 91% and intra-operative ultrasound in 93% of cases. All 5 occult tumours (indeterminate anatomical site before operation) were palpable at surgery and four of these were also correctly identified by intra-operative ultrasound. Site and size of tumour correlated poorly with pre-operative localisation. Operative procedure did not influence outcome with three patients needing re-operation. One patient died (5% mortality) and 9 patients (45%) had complications. Normoglycaemia has been obtained in all but one patient.

CONCLUSIONS

Insulinomas can be readily localised by systematic operative exploration. Non-invasive pre-operative investigations (ultrasonography/MRI) may help identify the location of tumour to determine the appropriate surgical procedure. Invasive pre-operative localisation tests like angiography and THPVS may be a valuable adjunct for re-operations. This also helps reduce the costs.

Multimodality preoperative imaging of pancreatic insulinomas

Pancreatic insulinomas are rare tumours of the islet cells of the pancreas, which account for the majority of functional neuroendocrine tumours of the pancreas. There is often a typical history of recurrent hypoglycaemic collapse and dizzy spells. Insulinomas are usually solitary, and the vast majority are intra-pancreatic in location. They are characteristically small with approximately 66% being less than 2cm at presentation. Insulinomas continue to pose a diagnostic challenge to physicians, surgeons and radiologists alike. The role of imaging is to detect and provide precise anatomical localization and staging of tumours prior to surgery. Due to their small size at clinical presentation, they are notoriously difficult to localize radiologically, and specifically designed protocols are necessary to aid detection. In this review, we describe the current "state of the art" imaging protocols that may be used in the preoperative localization of insulinomas.

The importance of preoperative localisation procedures in organic hyperinsulinism--experience in 67 patients

BACKGROUND

Preoperative localisation of insulinomas has been regarded unnecessary, given the significantly higher detection rates of intraoperative ultrasonography and bidigital palpation. These are mandatory before endoscopic surgery.

METHODS

67 patients operated on for organic hyperinsulinism were retrospectively analysed regarding tumour localisation within the pancreas, tumour size, histological findings, sensitivities of preoperative imaging methods, and surgical techniques.

RESULTS

59 patients (88%) had solitary insulinomas, four patients (6%) multiple insulinomas and four adult patients (6%) nesidioblastosis. Well-differentiated neuroendocrine tumours with benign behaviour (including four patients with nesidioblastosis) were diagnosed in 53 patients (79%), tumours with uncertain behaviour in nine patients (13%) and well-differentiated neuroendocrine carcinomas in five (8%). Tumours were evenly distributed throughout the pancreas. Endoscopic ultrasound localised tumours in 15 out of 21 patients (71%), conventional computed tomography (CT) in 7 out of 21 (33%), single-slice helical CT in 7 out of 12 (58%), multidetector CT in 5 out of 5 (100%), magnetic resonance imaging in 11 out of 13 (85%) and angiography in 15 out of 23 (65%). Various combinations of available methods achieved a sensitivity of 88% (49 patients true positive, 4 true negative, 7 false negative). Of 59 patients, solitary insulinomas were enucleated in 47 (80%), 11 patients underwent conventional open resection and one patient endoscopic distal pancreatic resection. Patients with nesidioblastosis or multiple tumours underwent pancreatic resections alone or in combination with enucleations.

CONCLUSION

After biochemical diagnosis of organic hyperinsulinism, preoperative localisation is necessary for planning endoscopic pancreatic surgery, because of the possibility of multiple insulinomas, malignancy or nesidioblastosis in adults.

Mangan-enhanced MR imaging for the detection and localisation of small pancreatic insulinoma

Insulinoma is the most common pancreatic endocrine tumor. Localization of small tumors remains a diagnostic challenge. Recently, Mangafodipir-enhanced MR imaging using a whole-body coil has been shown to be effective in the detection and staging of pancreatic cancer [3]. Localization of even small tumors is improved and surgical techniques, such as robotic-assisted surgery, have been made possible.

Surgical treatment of benign and borderline neoplasms of the pancreatic body

BACKGROUND

Conventional operations for benign and borderline tumors of the pancreatic body are distal pancreatectomy and enucleation. An unusual operation allowing the preservation of the proximal and distal pancreas is median pancreatectomy.

METHOD

A retrospective analysis of prospectively collected data on 67 patients with nonmalignant neoplasms of the pancreatic body was performed. The operations were: 32 median pancreatectomies (22 with duct occlusion of the distal pancreas, 10 with pancreaticojejunostomy), 21 distal pancreatectomies, and 14 enucleations. The operative and long-term outcomes of the different operations were compared.

RESULTS

Enucleation had a shorter operative time and less blood loss than the other operations. No mortality was observed. The pancreatic fistula rate was 50% after median pancreatectomy (59% in case of distal duct occlusion, 30% in case of pancreaticojejunostomy), 14% after distal pancreatectomy and 14% after enucleation. Diabetes appeared in 3 patients after distal pancreatectomy and 3 patients after median pancreatectomy with duct occlusion.

CONCLUSIONS

When indicated, enucleation is the operation of choice for a nonmalignant neoplasm of the pancreatic body. With respect to distal resection, the higher fistula rate of median pancreatectomy with pancreaticojejunostomy could be the price for a better long-term endocrine function; median pancreatectomy with duct occlusion had worse operative results and no long-term advantages.

The role of ultrasound in biliary and pancreatic diseases

The possibilities and the limits of transabdominal ultrasonography (US) in the diagnosis of bilio-pancreatic diseases are reviewed here in the light of the last 10 years' research. US remains the method of choice for the diagnosis of gallstones and is generally accepted as an initial imaging technique in gallstone complications, such as acute cholecystitis. Moreover the method can be useful for the detection of the biliary complications after laparoscopic cholecystectomy and after liver transplantation. US is still considered the first diagnostic procedure when stones are suspected in the common bile duct. The use of color Doppler can provide a differential diagnosis of gallbladder cancer with respect to other benign inflammatory or polypoid lesions. Color Doppler US allows to detect vascular complications of acute pancreatitis such as pseudoaneurysms. US is still considered useful for the initial screening of the pancreatic cancer. However, for staging other imaging techniques must be employed. With US useful informations are obtained in the diagnosis of cystic tumors of the pancreas and of pancreatic metastases. US is generally of little use for the diagnosis of endocrine tumors.

Imaging and localization of pancreatic insulinomas

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 the preoperative localization. All recent advances in imaging have improved the likelihood for curative surgical resection. Our purpose is to demonstrate the characteristics of all modalities, which may be used in the preoperative localization algorithm.

Islet cell tumor of the pancreas: biphasic CT versus MR imaging in tumor detection

PURPOSE

To compare the effectiveness of biphasic computed tomography (CT) and magnetic resonance (MR) imaging in the detection of pancreatic islet cell tumors.

MATERIALS AND METHODS

Retrospective quantitative, qualitative, and receiver operating characteristic analyses of biphasic CT and MR imaging were performed in 19 patients with 26 histopathologically proved islet cell tumors. Delayed arterial dominant-phase (AP) and portal venous-phase (PVP) biphasic CT was performed after the administration of contrast material. MR imaging included T1-weighted spin-echo (SE) and T2-weighted SE or fast SE imaging, fat-saturated T1-weighted SE imaging, dynamic contrast material-enhanced T1-weighted gradient-echo imaging, and delayed enhanced T1-weighted SE imaging with or without fat saturation.

RESULTS

PVP CT and delayed enhanced T1-weighted MR imaging had the highest A(z) values (0.98 and 0.97, respectively; P <.05). Delayed enhanced T1-weighted MR imaging had the highest relative sensitivity (14-15 [74%-79%] of 19 lesions), followed by PVP CT (18-19 [69%-73%] of 26 lesions), AP CT (17-19 [65%-73%] of 26 lesions), fat-saturated T1-weighted MR imaging (eight to 10 [57%-71%] of 14 lesions), T2-weighted (16-17 [62%-65%] of 26 lesions), T1-weighted (15-18 [58%-69%] of 26 lesions) MR imaging, and dynamic MR imaging (nine [56%] of 16 lesions).

CONCLUSION

Biphasic (especially PVP) CT and MR imaging have similar effectiveness in the detection of islet cell tumors if fat-saturated T1-weighted and delayed enhanced T1-weighted MR imaging are included.

Detection of small, functional islet cell tumors in the pancreas: selection of MR imaging sequences for optimal sensitivity

PURPOSE

To determine the sensitivity and specificity of magnetic resonance (MR) imaging for depicting pancreatic small, functional islet cell tumors and the minimum number of sequences for expedient diagnosis.

MATERIALS AND METHODS

Twenty-eight patients clinically suspected to have functional islet cell tumors underwent T1- and T2-weighted spin-echo (SE) MR imaging with and without fat suppression, T2-weighted fast SE imaging, and spoiled gradient-echo (GRE) imaging before and after injection of gadopentetate dimeglumine. Sensitivity, specificity, and the best and minimum number of sequences for definitive diagnosis were determined.

RESULTS

MR images depicted proved islet cell tumors in 17 of 20 patients (sensitivity, 85%). Images were true-negative in eight patients with negative follow-up examination results for more than 1 year. Specificity was 100%; positive predictive value, 100%; and negative predictive value, 73%. Among 20 patients with tumor, T1-weighted SE images with fat suppression and nonenhanced spoiled GRE images each showed lesions in 15 (75%); T2-weighted conventional SE with fat suppression, in 13 (65%); gadolinium-enhanced spoiled GRE, in 12 (60%); and T2-weighted fast SE, in seven of 10 patients (70%).

CONCLUSION

MR imaging accurately depicts small islet cell tumors. T2-weighted fast SE and spoiled GRE sequences usually suffice. Gadolinium-enhanced sequences are needed only if MR imaging results are equivocal or negative.

Utility of abdominal sonography in patients with idiopathic deep vein thrombosis

PURPOSE

Studies have confirmed an association between idiopathic deep vein thrombosis (DVT) and malignant tumors. We assessed the usefulness of routine abdominal sonography in patients with idiopathic DVT to detect malignant tumors and other relevant findings.

METHODS

We retrospectively analyzed abdominal sonograms and records from 135 consecutive patients with confirmed idiopathic DVT and interviewed patients and their physicians during the follow-up period (mean, 30 months). Malignancy and other clinically relevant findings determined by sonography were tabulated, and the cost of each malignancy detected by abdominal sonography in this study was calculated.

RESULTS

Malignant tumors were found in 14 patients (10%), 7 by routine abdominal sonography, 3 by other means during hospitalization, and 4 during the follow-up period. Other clinically relevant findings detected by routine abdominal sonography were found in 33 patients (24%). The estimated cost of discovering malignancy by using screening abdominal sonography was approximately US$3,000/malignancy.

CONCLUSIONS

Abdominal sonography was useful in detecting a variety of clinically relevant findings in addition to half of the malignant tumors found in our study.

Dual phase spiral CT in the detection of small insulinomas of the pancreas

Dual phase contrast enhanced spiral computed tomography (DPSCT) has the potential to improve detection of small insulin secreting islet cell tumours of the pancreas. Seven patients with biochemically proven insulinoma, who had previously undergone a range of negative radiological procedures, were referred for DPSCT. Images of the pancreas were obtained using 3 mm collimation in the arterial and arteriovenous perfusion phase following the rapid injection of contrast medium. Six tumours were localized in seven patients. The six insulinomas identified on DPSCT ranged in size from 6 mm to 18 mm and were located in the uncinate process (2), head (1), neck (2) and body (1). All six tumours were detected in the arterial phase and four in the arteriovenous phase. The four insulinomas detected on both perfusion phases were more conspicuous in the arterial phase in three patients and more conspicuous in the arteriovenous phase in one patient. In conclusion, high resolution arterial phase acquisition of the pancreas is very valuable in the detection of small insulinomas.