Bilateral hilar prominence on x ray means that the radiologist interpreting your x ray thinks that the hila are enlarged. The hila of the lung are the central middle part of the lung. This is where the bronchi or airways, nerves, blood vessels and lymph nodes converge. Bilateral means both the right and left side. Sometimes one side gets enlarged but this article will cover when it happens on both sides.
The radiologist will use his experience to determine whether your hila are enlarged. There is no measurement to say they are enlarged. Most commonly, this finding is caused by big lymph nodes. Other causes can include enlargement of the pulmonary arteries which can be seen with pulmonary hypertension. When your heart is not working well or you have congestive heart failure, the veins can enlarge and cause this finding. Sometimes this finding can be due to your normal anatomy.
Lymph nodes are part of your immune system and enlarge in response to infections, inflammatory conditions and cancer. Therefore, infections with fungus or Tuberculosis are some conditions that will enlarge the lymph nodes on both sides. Cancer such as lymphoma is another cause. If you have cancer somewhere else in the body, this can be caused by metastasis or spread of the cancer. Sarcoidosis is an inflammatory disease that can involve the lymph nodes and cause them to enlarge on both sides.
Most of the time, the radiologist interpreting your x ray as bilateral hilar enlargement will recommend a ct scan. This will allow a closer look and perhaps discover the cause of the hilar enlargement. Other times, it may not be clear and further testing may be needed including blood work, a pet scan, biopsy, or follow up. Your doctor will know your history and will know what is most likely and what the work up should be.