Health Dictionary
Reliable, easy-to-read patient information on common medical conditions — written in plain language, free of jargon, and grounded in current evidence. Browse the most frequent diagnoses, understand what they mean for everyday life, and learn which steps and questions help you have a focused conversation with your doctor.
Adenoma CT
Introduction
Overview
Overview
Unenchanced CT
- Adrenal adenomas appear as small (<3 cm), well-defined homogeneous masses that are typically hypoattenuating relative to the liver.
- At an attenuation value of less than 0 HU at unenhanced CT, the diagnosis of an adenoma can be made with 100% confidence; however, this threshold has only 47% sensitivity.
- At cutoff of 18 HU, a diagnosis of adenoma was made with 100% specificity and 85% sensitivity, compared to the specificity:sensitivity ratio of 68%:100% with a more conservative cutoff of 10 HU.
- A rational approach advocated by some authorities is to choose the CT number threshold on the basis of the patient’s risk for metastatic disease. For example, a threshold of 10 HU could be applied to older patients or to those with known primary malignancies. A threshold of 18 HU could be applied to younger patients without underlying cancer.
Enhanced CT
- Lipid-poor adenomas are more difficult to diagnose because the CT numbers increase and approach those of soft tissue.
- Contrast-enhanced imaging with 10-minute-delayed CT scans may be helpful in these cases.
- By using a threshold of 30 HU, the sensitivity and specificity for delayed contrast-enhanced CT in the characterization of benign disease are 80% and 100%, respectively.
- A relative percentage washout of more than 50% in the delayed study represents a sensitivity and specificity of 98% and 100%, respectively, for the detection of adenoma.
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]