Retrograde lymphatic pressure experiments on the human thoracic duct in Thiel embalmed specimens: Using short alternating pressure sequences, combined with microscopic video recordings.

BACKGROUND

More accurate data of the anatomical location of the lymphatic system in relation to the surrounding anatomy is required to optimize radiotherapy treatment planning. To accurately visualize/map these anatomical relationships in 3D, contrast agent needs to be injected into the lymphatic vessels, so they are visible on medical imaging data (CT/micro-CT). Retrograde lymphatic injections (injections against the lymphatic flow/valve direction) have theoretical advantages for lymphatic mapping studies, but more data on lymphatic vessel wall and valve behavior is needed to optimize retrograde lymphatic injection methodologies.

METHODS

Quickly alternating (30 sec) infusion pressures were tested on thoracic duct specimens and experiments were recorded using a surgical microscope. Manual injection was added after each pressure sequence.

RESULTS

Infusion pressures up to and including 25 mmHg frequently showed retrograde filling. Above pressures of 25 mmHg, retrograde filling was rare and lymphatic valves frequently withstood infusion pressures of up to 75 mmHg. Microscopic video recordings proved very useful for data analysis.

CONCLUSIONS

Quickly alternating infusion pressures did not stimulate valve breakage, but seemed to protect lymphatic walls from ruptures at higher pressures. A distinction between inherently weak valves, and strong valves that can withstand infusion pressures of up to 75 mmHg was uncovered. Retrograde filling sometimes coincides with antegrade filling, depending on lymphatic network organization, but this can be beneficial for lymphatic mapping. Flow through lymph nodes should be studied in more detail in future retrograde injection studies, since different types of lymph nodes were encountered that showed distinct filling patterns.