Diagnostic and Therapeutic Role of Endoscopic Ultrasound (EUS) in a CT-Negative Occult Insulinoma

Chee Kit Tee; Yong Siang Ng; Noor Hafis Md Tob; Norhaliza Mohd Ali

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Diagnostic and Therapeutic Role of Endoscopic Ultrasound (EUS) in a CT-Negative Occult Insulinoma

Author: Chee Kit Tee ¹ ; Yong Siang Ng ¹ ; Noor Hafis Md Tob ¹ ; Norhaliza Mohd Ali ¹
Author Information

1. Hospital Sultanah Aminah Johor Bahru
Publication Type:Journal Article
MeSH: Insulinoma; Tomography, X-Ray Computed
From: Journal of the ASEAN Federation of Endocrine Societies 2026;41(S1):87-88
CountryPhilippines
Language:English
Abstract: Introduction:A negative computed tomography (CT) scan does not preclude an insulinoma, as small lesions frequently remain undetected on conventional imaging. This case highlights the indispensable role of endoscopic ultrasound (EUS)— not just for localizing occult tumors, but as a definitive, minimally invasive therapeutic alternative to high-risk surgical resection.
Case:A 39-year-old female with underlying hypertension presented with a 5-month history of predominantly fasting hypoglycemia (glucose <3.0 mmol/L) and neuroglycopenic symptoms, fulfilling Whipple’s triad. A supervised 72-hour fast confirmed endogenous hyperinsulinemic hypoglycemia at 31 hours, with a nadir glucose of 1.4 mmol/L, insulin 116 pmol/L, and C-peptide 821 pmol/L. Notably, contrastenhanced CT of the pancreas was reported as normal. To overcome this, EUS was performed, successfully identifying a hidden 19 × 18 mm lesion in the head of the pancreas, intimately abutting the main pancreatic duct. Despite medical therapy with diazoxide and strict dietary modifications, her hypoglycemia remained refractory. Given the tumor’s proximity to the main pancreatic duct, surgical enucleation carried a prohibitively high risk of complications. Consequently, she underwent EUS-guided radiofrequency ablation (RFA). Immediate post-procedure outcomes demonstrated near-complete resolution of the hypoglycemic episodes. Diazoxide was subsequently stopped. Outpatient continuous glucose monitoring confirmed sustained normoglycemia and marked symptom resolution, with no procedure-related complications.
Conclusion:The absence of a pancreatic lesion on CT demands persistent clinical suspicion in cases of biochemically proven hypoglycemia. EUS remains paramount for detecting occult lesions missed by standard imaging. Importantly, EUSRFA serves as a highly effective, tissue-sparing alternative to surgical resection for insulinomas, especially when conventional surgery poses prohibitive anatomical risks.
Full text:2026080414370799222EP_A123.pdf