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Abstract

Abstract


Insulinomas are rare, usually benign, solitary tumours accounting for 60% of islet cell tumours. These tumours can be difficult to localize preoperatively due to their small size. We present a challenging case of a 40 year old male with frequent hypoglycaemic spells and endogenous hypoglycaemia who presented as a diagnostic dilemma. Patient had an occult insulinoma with inconclusive CT Abdomen, MRI Abdomen and Octreotide scan. The final localization of the tumour was made by  selective arterial calcium stimulation testing (SCAT), done for the first time in Pakistan at Aga Khan University Hospital. This was followed by successful distal pancreatectomy as localizd by SACT yielding a well differentiated neuroendocrine tumour. After surgery patient made a robust recovery with no further hypoglycaemic symptoms. Hence successful localization and management of occult insulinomas can be challenging but can be achieved with the advent of newer invasive modalities.

Keywords: Insulinomas, Hypoglycemia, Neuroendocrine tumour

DOI: https://doi.org/10.5455/JPMA.19325

 

Introduction

 

The first insulinoma was described by an orthopaedic surgeon, Wider and colleagues in 1927, who experienced frequent neuroglycopenic symptoms due to prolonged fasting in the operating room.1 Insulinomas are rare tumours with an incidence of 4 patients per 1 million /year and accounts for 60% of islet cell tumours.2 They are typically solitary tumours with 90% measuring less than 2 cm. They can also present as a benign multicentric disease in patients with MEN 1.3 Due to their nonspecific, occasionally bizarre symptoms these tumours can disguise themselves with various neuropsychiatric conditions.4 An occult insulinoma refers to a biochemically proven tumour with an undetermined anatomical site before surgery.5 Their small size and difficult preoperative localization along with nonspecific symptoms poses a diagnostic dilemma to both the endocrinologists and surgeons. We present a case of a 40 year old male with an occult insulinoma which after a rigorous but futile imaging work up was finally localized by Selective Calcium Arterial Stimulation Testing (SCAST), done first time in the history of Pakistan at Aga Khan University Hospital. The consent of the patient was taken prior to the manuscript writing.

 

Case

 

A 44 years old male known case of Hypothyroidism and Hypertension presented to our endocrine clinic for the first time in June 2017 with episodes of recurrent sweating, tremors, palpitations and generalized weakness. Patient had these symptoms since last 2 years, observed during fasting and relieved with food intake. During these episodes his glucose went down to 35 -40mg/dl. He combated with these spells of hypoglycaemia with instant intake of choclates or sugar but did not seek any professional help, due to excessive binge eating there was a noticeable weight gain over this two year period.  He had a past history of pulmonary tuberculosis, treated few years back. Family history was positive for diabetes, hypertension, coronary artery disease and breast carcinoma. His medication history included Olmesartan 40 mg OD and thyroxine 150 mcg OD. His multiple Serum insulin, C- peptide, blood glucose done during 2 years period were clearly suggestive of endogenous hypoglycaemia. Patient had a BMI of 31.5kg/m2. Rest of his physical examination was unremarkable. On the basis of history and biochemical evaluation diagnosis of Spontaneous hypoglycaemia secondary to endogenous hyperinsulinaemic hypoglycaemia was made and patient was advised CT scan abdomen (Pancreatic protocol) which showed no pancreatic mass following which he was asked to get MRI abdomen as next line investigation which also did not reveal any pancreatic , hepatic or other masses. He then underwent Somatostatin receptor scintigraphy with no uptake in pancreas or liver. Patient was then planned for Angiography of Coeliac and Superior mesenteric arteries to look for tumour blush followed by Selective Calcium Arterial Stimulation Testing (SCAST). This test involved the femoral vein and artery cannulation with passage of a sampling catheter to the right hepatic vein for sampling of insulin and sequentially under fluoroscopic guidance, a catheter placed into the splenic, superior mesenteric and gastroduodenal arteries to allow injection of calcium gluconate into these arteries. A positive response was defined as at least a doubling of the insulin level after injection calcium gluconate at more than one time point.

SCAST with venous sampling after calcium infusion showed many folds increase in insulin, C peptide levels in the splenic artery thus pointing towards the culprit lesion in the body or tail of his pancreas (Table).

Patient was then referred to an experienced surgeon with the plan of a pancreactic enucleation if the tumour could be localized on peroperative ultrasound otherwise distal pancreactomy being the second option. As the adenoma could not be localized on peroperative ultrasound therefore he underwent distal pancreatectomy. His histopathology report showed a well differentiated neuroendocrine tumour, grade 1 of distal pancreas with a size of 1.5X1.3 cm, Ki-67 index of