The doughnut sign can be appreciated on the lateral chest radiograph of patients with mediastinal adenopathy, most commonly seen in pediatric patients with pulmonary tuberculosis infection1.
The sign is made up of precarinal, subcarinal and retrocarinal lymph nodes which surround the radiolucent trachea and upper lobe bronchi, giving the doughnut-like appearance.
- 1. Andronikou, S., van der Merwe, D., Goussard, P., Gie, R., & Tomazos, N. 2012 Sep 10. Usefulness of lateral radiographs for detecting tuberculous lymphadenopathy in children – confirmation using sagittal CT reconstruction with multiplanar cross-referencing. South African Journal of Radiology. [Online] 16:3