Pre- and intraoperative localization of insulinomas: report of 22 observations

Ectopic insulinoma in a dog with insulin-induced hypoglycemia: a case report

A 7-year-old spayed female Shih Tzu dog was presented for evaluation of recurrent hypoglycemia. Serum insulin levels during hypoglycemia were 35.3 μIU/mL. Ultrasonography and computed tomography showed a mesenteric nodule between the kidney and the portal vein, but no pancreatic mass was observed. During surgery, the nodule had neither anatomical adhesions nor vascular connections to the pancreas. Pancreatic inspection and palpation revealed no abnormalities. Hypoglycemia improved after resection of the nodule. Histopathological examination confirmed the nodule to be an islet cell carcinoma. Although extremely rare, ectopic insulinoma should be considered as a possible cause of insulin-induced hypoglycemia in dogs.

Essentials of Insulinoma Localization with Selective Arterial Calcium Stimulation and Hepatic Venous Sampling

Insulinomas are the most common functional pancreatic neuroendocrine tumor. Most insulinomas can be localized non-invasively with cross-sectional and nuclear imaging. Selective arterial calcium stimulation and hepatic venous sampling is an effective and safe minimally-invasive procedure for insulinoma localization that may be utilized when non-invasive techniques are inconclusive. The procedure’s technical success and proper interpretation of its results is dependent on the interventional radiologist’s knowledge of normal and variant pancreatic arterial perfusion. Accurate pre-operative localization aids in successful surgical resection. Technical and anatomic considerations of insulinoma localization with selective arterial calcium stimulation and hepatic venous sampling are reviewed.

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.

Intraoperative ultrasound with palpation is still superior to intra-arterial calcium stimulation test in localising insulinoma

AIM

This study assessed the sensitivities of preoperative localisation modalities such as computed tomography (CT), magnetic resonance imaging (MRI), arteriography and arterial stimulation venous sampling (ASVS) using serum insulin and C-peptide gradients to intraoperative techniques in localising insulin-secreting tumours in our institution.

METHODS

Fourteen patients with proven insulinoma, aged 20-66 years, who presented from 1997 to 2004, were studied retrospectively. All patients underwent ASVS where C-peptide and/or insulin gradients were calculated. The results were compared with the preoperative findings of CT, MRI, arteriography, as well as intraoperative ultrasound and palpation.

RESULTS

Intraoperative ultrasound with palpation correctly localised 10 of the 11 tumours with a sensitivity of 91%. Sensitivities of other localisation techniques were lower: 31% by CT, 50% by MRI, and 46% by arteriography. ASVS with insulin gradients alone allowed accurate localisation in 40% of patients while localisation using only C-peptide gradients of more than 2 was 43%. The insulinomas, measuring 10-30 mm, were successfully removed in 13 patients--6 from the body, 4 from the tail, 2 from the head and 1 from the junction of the body and tail. All except 1 were cured by selective surgery and remained free of hypoglycaemia over the next 2-60 months of follow-up. One patient had left lobectomy due to liver metastases from a malignant insulinoma and remained asymptomatic with medical therapy.

CONCLUSIONS

Intraoperative ultrasound with palpation is a highly sensitive method for the localisation of insulinoma compared with other preoperative localisation techniques.

Insulinoma in Iran: a 20-year review

BACKGROUND

The time between onset of symptoms of insulinoma to diagnosis ranges from 10 days to more than 20 years. To help physicians make an earlier diagnosis, we defined the clinical, imaging and paraclinical characteristics of insulinoma in cases from seven referral hospitals in Iran over two decades.

METHODS

The medical records of 68 cases with biochemical or histological evidences of insulinoma were reviewed.

RESULTS

More males were affected (53%). The mean age at diagnosis was 39 +/- 15.3 years. The mean duration of symptoms was 39.9 +/- 59.3 months. Eighty-four percent of patients had been initially misdiagnosed as cereberovascular accident (CVA), epilepsy, conversion disorder, and others). Neuroadrenergic symptoms were observed in 89.6% and and neuroglycopenic symptoms in 97% of patients. Mean diameter of tumours was 2.9 cm (range, 1 cm to 8.5 cm). Of 52 pathologically confirmed cases of insulinoma, 43 tumours (87.8%) were single and 49 (94.2%) were benign. Fifty-five patients had undergone surgery, with a successful outcome in 44 (80%).

CONCLUSION

The high incidence of neuroglycopenic symptoms suggest the clinical impression of insulinoma when patients present with a suggestive clinical syndrome. The clinical impression is essential to decrease the frequent delay in the diagnosis of insulinoma.

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.

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

BACKGROUND

Preoperative radiologic localization of insulinomas often fails because of the small size of these tumors. Endoscopic ultrasound (EUS) can localize insulinomas in up to 80% of the cases. The aim of this study was to compare EUS and computed tomography (CT) diagnostic accuracy for insulinomas.

METHODS

We reviewed medical records from 12 patients (10 women) with a biochemical diagnosis of hypoglycemia and hyperinsulinism from 1 university hospital and 1 community hospital. A diagnosis of insulinoma was ultimately made in all cases and before surgery the patients underwent abdominal US, spiral CT and EUS in an attempt to precisely localize the tumor. Surgery was considered the standard for tumor localization.

RESULTS

Ten tumors were benign (83.3%) and 2 were malignant (16.7%). The overall sensitivity of EUS in identifying insulinomas was 83.3% compared with 16.7% for CT. Tumors not detected by EUS had a mean size of 0.75 cm. EUS-guided fine-needle aspiration was possible in only 3 patients, with a positive cytologic diagnosis in 2 (66.6%). Tumors located in the head and body of the pancreas were identified by EUS in all patients, but those located in the tail were diagnosed in only 50% of the cases.

CONCLUSIONS

EUS is superior to spiral CT and should replace it for the detection of pancreatic insulinomas. EUS identification depends on the site and size of the tumor.

Evaluation of preoperative and intraoperative arterial stimulation and venous sampling for diagnosis and surgical resection of insulinoma

BACKGROUND

The precise intraoperative localization of insulinoma is essential for successful surgical treatment. In addition to various imaging modalities developed recently, arterial stimulation and venous sampling (ASVS) has also been used for tumor localization.

METHODS

Preoperative and intraoperative ASVS procedures were performed in 6 patients with insulinoma. Intraoperative ASVS was performed before and after tumor resection. Immunoreactive insulin (IRI) concentrations and the IRI ratio (IRI concentration at each time interval after calcium injection/baseline IRI concentration) were determined by the conventional or a quick IRI method.

RESULTS

The site of the tumor was identified preoperatively in all patients. The peak of the IRI ratio varied widely, but setting the cutoff value at 3.0 clearly differentiated peak IRA ratios in feeding arteries from those of nonfeeding arteries. Intraoperative ASVS showed a similar elevation of IRI levels, but the elevation disappeared after tumor resection in all but 1 patient. In 2 patients, resection of the tumor was confirmed during surgery by measuring IRI levels by the quick IRI method.

CONCLUSIONS

A combination of ASVS and conventional imaging modalities is useful for precise localization of insulinoma. Resection of the tumor can be confirmed intraoperatively by comparing IRI levels associated with preoperative and postresective ASVS.

Insulinoma: a review of current management

Insulinomas are a relatively rare tumour which occur predominantly in the pancreas. The majority of the tumours are benign, but have profound effects upon the patient. The diagnosis of insulinoma is often elusive, and the management may involve demanding surgery with a significant morbidity. In this review article, all clinical aspects of insulinomas are examined. Particular emphasis is placed on the myriad modes of presentation, and the methods used to localise the tumour pre-operatively. Medical, as well as surgical treatments are discussed and their role in the management of both malignant and benign tumours. Despite potential difficulties encountered in managing patients with this tumour, a large majority may be either cured or achieve useful palliation.

Imaging islet cell tumours

The localization of islet cell tumours presents a challenge to the radiologist and requires meticulous attention to detail in both technique and interpretation. As several imaging techniques are capable of demonstrating the tumour and none is absolutely accurate, a rational approach to the localization of these tumours requires a careful consideration of cost, sensitivity and the availability of special expertise. In almost all cases, initial imaging is performed with a combination of transabdominal ultrasound and CT. This will demonstrate the tumour and any hepatic metastases in about 40% of gastrinomas, 80% of insulinomas and almost all other functioning and non-functioning tumours. Where these tests are negative or equivocal, arteriography (which may be combined with ASVS) is the next line of investigation. If the tumour remains undetected, it is likely to be a small insulinoma or gastrinoma. Further investigation is dependent on local practice and the tumour type. Endoscopic ultrasound is rapidly emerging as a technique of high sensitivity in detecting small pancreatic tumours and may also demonstrate extrapancreatic gastrinomas. Transhepatic venous sampling and somatostatin receptor imaging have the advantage that they are not directly dependent on tumour size and they are particularly applicable to difficult cases where other imaging modalities are negative. TPVS is invasive and, while sensitive for insulinomas, is frequently unhelpful in gastrinomas. Somatostatin receptor scintigraphy, on the other hand, is more sensitive for gastrinomas. In future, MRI may prove to be at least as accurate as CT but as yet its exact role is uncertain. At the time of surgery, intraoperative ultrasound is a useful adjunct to palpation, and may avoid a standard distal pancreatectomy in patients with insulinoma.

Is preoperative radiographic localization of islet cell tumors in patients with insulinoma necessary?

Preoperative localization tests [sonography, computed tomography, angiography, percutaneous transhepatic portal venous sampling for insulin radioimmunoassay (PTP)] have a sensitivity of 60% to 90% in cases of organic hyperinsulinism. In all publications, however, the sensitivity of intraoperative localization, 75% to 100%, is distinctly higher. With the exception of PTP, all tumors that can be identified by preoperative localization can also be detected using palpation or intraoperative sonography. Preoperative localization diagnosis is therefore not absolutely necessary prior to primary operation in the case of organic hyperinsulinism. It is requested by many surgeons because: (1) only a few clinics have extensive experience with patients with an organic hyperinsulinism; (2) only a few clinics have extensive experience with intraoperative sonography; (3) the accuracy of palpation is improved following appropriate preoperative localization; and (4) in rare cases, the results of a PTP influence the operative procedure.

Intraoperative ultrasonography in pancreatic cancer

Intraoperative ultrasonography (I.US) has been introduced in order to overcome the limits of the preoperative imaging modalities (notably, ultrasonography and computed tomography), both in pancreatic cancer diagnosis and staging. The authors' experience encompasses 32 cases, selected according to the following criteria: lesions that could not be detected both preoperatively and at surgical exploration; lesions detected but not properly characterized, requiring differential diagnosis between cancer and pancreatitis; tumoral lesions with a perspective of radical surgery, in which the preoperative judgment of resectability had to be verified. In the only case of the first group, I.US allowed the identification of a small cancer in a jaundiced patient. In the 11 cases of the second group, I.US-guided fine-needle aspiration biopsy showed three cancers; however, among the other 8 lesions classified as pancreatitis there was one false negative diagnosis (a tumoral mass with liver metastases was demonstrated by computed tomography 6 mo later). Regarding the intraoperative staging of the proven cancers (20 cases of the third group; 4 cases of the first and second groups), I.US changed the planned surgical approach in 9 cases (showing vascular involvement or detecting liver metastases and enlarged lymph nodes not seen preoperatively); in 12 cases it confirmed the possibility of radical surgery. Finally, in the remaining 3 cases, I.US provided dubious information: only vascular dissection during surgery could achieve a correct evaluation, ruling out vascular involvement and thus allowing tumor resection.

Endoscopic ultrasound for localisation of islet cell tumours

In a prospective study endoscopic ultrasound localisation of pancreatic endocrine tumours was attempted in 21 patients with clinically suspected islet cell tumours. Most patients were referred after the failure of conventional imaging methods. Endoscopic ultrasound correctly identified the site of 12 of 15 insulinomas, one glucagonoma, and a diffuse pancreatic abnormality in a patient with multiple endocrine adenopathy. There were two true negative examinations and one technical failure. The sensitivity of endoscopic ultrasound was much greater than that of computed tomography or conventional transabdominal ultrasonography.

Pancreatic disorders in infancy and childhood: experience with 92 cases

Ninety-two children with pancreatic disorders were treated over a 10-year period. Thirty-three had blunt trauma, while 69 had medical, metabolic, or neoplastic diseases. Children with trauma had either duct disruption (3), gland fracture (4), or pseudocysts formation (26). Operation was required in 30. Pseudocysts were treated with observation alone in three cases, ultrasound-guided percutaneous aspiration in three, surgical external drainage in two, distal pancreatectomy in four, cyst gastrostomy in ten, and cyst-Roux-en-Y jejunostomy in six. Other disorders included pancreatitis (44), neoplasms (10), nesidioblastosis (4), and pancreaticosplenic abscess (2). Treatment for neoplasms included surgical excision in nine and biopsy in one (adenocarcinoma). Patients with nesidioblastosis underwent 95% (near total) pancreatic resection (two after previous unsuccessful 80% resection). Pancreatitis was familial in two cases, necrotizing in two, idiopathic in 11, and secondary to medications in six cases (steroids, 2; L-asparaginase, 4), gallstones in 17, and choledochal cysts in 6. Pancreatitis resolved after observation and conservative therapy in ten idiopathic cases, 4/6 medication-related cases, and following correction of biliary tract disease (15/17) or choledochal cysts (6). Pancreatic resection or drainage was required in the remaining cases. Pancreatic disorders can be accurately detected with computed tomography (CT) scan in most cases (excluding insulinoma). Ultrasound (US) is useful in cases of biliary tract disease and pseudocyst formation. Traumatic pseudocysts can resolve spontaneously or with US-guided percutaneous drainage (in the presence of normal ducts). Children with neoplasms, abnormal pancreatic ducts, or recurrent pancreatitis require resection or appropriate drainage procedures. Overall survival was 95%.