Incidental Adrenal Finding on a Low-Dose CT
A 61-year-old woman with a history of breast cancer is undergoing a PET/CT for restaging. The CT is a low-dose, non-contrast study for attenuation correction. On review, the technologist notices a 2.5 cm low-attenuation (fat-density) left adrenal nodule. The PET shows no FDG uptake above background in the adrenal gland. The patient's prior contrast-enhanced CT from 2 years ago described a left adrenal nodule measuring 2.2 cm with fat density. The ordering oncologist is not on site, and the report will be read by a teleradiologist.
1. How should the technologist handle the adrenal finding on a non-contrast, low-dose CT?
Read the worked answer
Recognize it, do not overcall it, and ensure it reaches the reader.
- A 2.5 cm fat-density adrenal nodule is characteristic of a myelolipoma or other fat-containing lesion; fat density on non-contrast CT is a benign feature. The absence of FDG uptake further supports a benign etiology.
- The low-dose CT is not a diagnostic CT, so the technologist should not attempt to characterize the nodule beyond noting it. The finding and its measurements should be communicated to the interpreting physician (and the ordering oncologist if policy requires) so it is included in the report and compared with the prior.
- Document the finding, the prior comparison (2.2 cm vs 2.5 cm), and the lack of FDG uptake.
2. What is the significance of comparing with the prior contrast-enhanced CT?
Read the worked answer
The comparison changes the interpretation.
- The prior study already described a fat-density adrenal nodule at 2.2 cm. Stability over 2 years and persistent fat density strongly favor a benign lesion (e.g., myelolipoma) rather than metastasis.
- A 0.3 cm interval change is within measurement variability on different scanners and techniques; it should not by itself prompt intervention.
- The technologist should ensure the prior study is available to the reader and flag the comparison, since the teleradiologist may not have it loaded.
3. What if the CT had shown a 2.5 cm soft-tissue (non-fat) adrenal nodule with no FDG uptake?
Read the worked answer
The approach would differ substantially.
- A non-fat adrenal nodule in a patient with known malignancy raises concern for metastasis, and further characterization (dedicated contrast-enhanced CT with washout, MRI, or biopsy) may be warranted per the care team.
- Absence of FDG uptake is reassuring but not definitive; small or necrotic metastases can be FDG-negative. The technologist's role is to ensure the finding and its characteristics (size, attenuation) are clearly communicated, not to decide management.
- The contrast between the fat-density and soft-tissue scenarios illustrates why the technologist must document attenuation characteristics rather than just size.