My child has a lump: Why did our pediatrician order an ultrasound?

Image: Ultrasound obtained behind the knee of a young child with a soft bump shows a round cyst (white arrow) with a “tail” (yellow arrow) extending deep toward the joint between the muscles. This is a typical appearance and location for a benign cyst (also known as a Baker cyst at this location).

A newly noted lump or bump in a child is a common concern brought by parents to pediatricians. Depending on your child’s symptoms and physical exam findings, your child’s pediatrician may order an ultrasound to gather more information about the underlying problem.

Image: Ultrasound obtained at the front of the knee in a young child with swelling shows a fluid collection in the knee joint that contain debris (white arrow). The femur is noted by the yellow arrow. This patient was ultimately diagnosed with an inflammatory condition of the joints.

Ultrasound is a fantastic way to take a deeper look at what could be causing the issue, particularly in a young child. The advantages of ultrasound in this scenario are numerous, including:

• Ultrasound uses sound waves to create images (rather than ionizing radiation), such that radiation exposure is not a concern.
• It can be performed whether the child is asleep or awake, so that no sedation/anesthesia is required to complete the exam. Our Radiology Department can easily provide toys or movies to help distract your child during the exam.
• No IV access is required for the exam.
• Ultrasound has wonderful resolution of the soft tissues underneath the skin.
• It excels at identifying and characterizing structures with high fluid content, including cysts, blood vessels, and tissues with a high fluid content (like cartilage, of which there is an abundance in young children).
• Looking at the unaffected side (such as the opposite arm or leg for a normal comparison) is also easily done with ultrasound.
• It may also to be important to see how the bump changes in real-time with certain movements or with applied pressure (such as with a fluid collection or hernia). This is more easily done with ultrasound than any other type of imaging exam.

Related Article: Ultrasounds and Bladders: What’s the Connection?

After the ultrasound technologist scans the patient and shows the images to the radiologist, the radiologist may come in to obtain more images and ask more questions about what you have noticed about the bump. Once the radiologist has finished scanning, he or she will likely be able to give you some ideas about the underlying cause for the lump. A specific diagnosis may be clear, or further testing (such as an MRI) may need to be done in the next few weeks to gather more information. Sometimes, a follow-up clinical exam or ultrasound may be indicated. Rarely, a child may need to be scheduled for a biopsy/removal of any associated mass. Regardless, the radiologist will often be able to tell you what he or she is going to report to your child’s pediatrician and may be able to give you a general idea about what to expect next from the ordering pediatrician. It is, of course, completely appropriate to ask questions of the radiologist before he or she leaves the room—we are happy to give you as much information as possible!

Contributed by Dr. Carl Merrow Jr. and edited by Glenn Miñano, BFA.