Ultrasound-guided needle positioning confirmation with injection of saline solution for nodal dynamic contrast-enhanced MR-lymphangiography in pediatric patients.

Purpose: To assess the success rate of confirmation of ultrasound-guided intranodal needle positioning by saline injection for dynamic contrast-enhanced magnetic resonance lymphangiography (DCMRL) in pediatric patients.

Material and methods: Data from children undergoing nodal DCMRL after ultrasound-guided needle positioning into inguinal lymph nodes and validation of the needle position by injection of plain saline solution between 05/2020 and 12/2022 were reviewed. On injection of saline solution, adequate needle position was confirmed by lymph node distension without leakage. Detection rates and lymph node diameters were recorded. Technical success of needle placement was defined as enhancement of ipsilateral iliac draining lymph vessels on DCMRL, while clinical success was based on enhancement of central lymphatics and/or lymphatic pathologies being observed.

Results: One hundred sixteen DCMRL were performed in 90 children (58 male, mean age 6.1 years, range 3 weeks-18 years). In 232/232 groins lymph nodes were identified on ultrasound with a mean diameter of 2.5 mm (smallest diameter 1 mm in n = 24 patients). Due to skin inflammation, no puncture was performed in 2/232 groins. Saline injection showed lymph node distension in 230/230 punctured nodes. On MR contrast injection enhancement of draining lymph vessels was seen in 228/230 nodes. In 1/230 nodes, in-bore needle retraction led to lymphatic enhancement, so a total of 229/230 needle placements were technically successful. One of the 230 DCMRLs was successful with only a unilateral contrast application. Overall, 116/116 DCMRLs were clinically successful.

Conclusion: Confirmation of ultrasound-guided needle positioning for nodal DCMRL using saline injection is a reliable technique with a very high success rate in pediatric patients with small lymph nodes.

Key points: Question Evaluation of ultrasound-guided injection needle positioning for dynamic contrast-enhanced MR-lymphangiography in children requires validation. Findings Confirmation of needle positioning by ultrasound-guided saline injection is a reliable technique with a very high success rate for MR-lymphangiography in pediatric patients. Clinical relevance Intranodal needle position for dynamic contrast-enhanced lymphangiography can be confirmed with a very high success rate using saline injection alone in a pediatric cohort.