Purpose or Case Report: Inguinal lymph node identification using ultrasound is critical in performing intranodal lymphangiography. We routinely utilize a 15 MHz “hockey stick” linear high resolution ultrasound probe (Philips Epic 7) for identification as well as to gain needle access into the inguinal lymph node. However in children with severe body wall edema and in low weight premature babied identification of lymph nodes can be difficult and sometimes impossible. Higher frequency ultrasound transducers offer the potential for improved identification of lymph nodes in such cases. The aim of this study was to compare imaging finding of high resolution US probe to the traditional 15 mHz probe in patients undergoing lymph node access for lymphangiography.
Methods & Materials: This is a retrospective comparison of ultrasound images obtained with both 15 MHz linear probe as well as high frequency 40 MHz transducer (Visualsonics Vevo) in patients undergoind inguinal lymph node access for lymphatic imaging and intervention procedures between October 2018 and October 2019. Images were compared for resolution, ease of identification of node, lymph node characteristics and intra nodal needle position.
Results: A total of 15 patients (30 lymph nodes) were included in the study from. Age range included 4 days to 5 years. In all 15 patient, 30 lymph nodes were identified using the 40 MHz probe, however only 24 lymph nodes (80%) were identified using the 15 MHz transducer. Out of the 24 lymph nodes identified using the 15 MHz transducer, 4 lymph nodes (13%) had poorly defined architecture that blended with surrounding fat due to previous injection. These 4 nodes (13%) had a clearly identifiable architecture using the 40 MHz transducer.
Conclusions: The 40 MHz transducer has a superior resolution and can be used to easily identify inguinal lymph nodes even in neonates. Intra nodal needle position at least in some cases is better confirmed using the 40 MHz transducer. Finer details of lymph node including intranodal vessels and efferent lymph vessel are clearly seen with 40 MHz transducer and further studies are required to know the importance of visualizing these structures related to lymphatic access.