American Board of Internal Medicine (ABIM) Certification Practice Exam

How can insulinoma be diagnosed?

1. Magnetic resonance imaging

2. Endoscopic ultrasound

3. Barium swallow test

4. CT scan of the abdomen

The correct answer is: Endoscopic ultrasound

Insulinoma, a rare neuroendocrine tumor of the pancreas that secretes insulin, is typically diagnosed through specific imaging techniques that can visualize pancreatic masses. Endoscopic ultrasound is particularly useful for identifying small insulinomas, which may not be easily detected through other imaging modalities. This technique involves a thin, flexible tube with an ultrasound probe that is inserted into the stomach or duodenum, providing high-resolution images of the pancreas and surrounding structures. Endoscopic ultrasound is advantageous due to its ability to visualize small tumors (usually smaller than 2 cm) and assess their location accurately, as well as evaluate any potential invasion into surrounding tissues. Additionally, it allows for fine-needle aspiration, enabling cytological evaluation to confirm the diagnosis. In contrast, while magnetic resonance imaging and CT scans of the abdomen can also be employed to detect pancreatic tumors, they may not be as sensitive as endoscopic ultrasound for small lesions like insulinomas. The barium swallow test, primarily used to evaluate esophageal and gastric motility or structural abnormalities, does not play a role in diagnosing insulinomas. Thus, the choice of endoscopic ultrasound is the most appropriate and effective for diagnosing insulinoma, highlighting its specificity and sensitivity for this particular type of tumor.