1. In this proof-of-concept study, central thoracic magnetic resonance lymphangiography (MRL) was successfully used to characterize the presence or absence of disease within the central lymphatic vessels in a small series of patients.
Evidence Rating Level: 4 (Below Average)
Study Rundown: Lymphatic pathology, whether congenital or acquired, can lead to lymphedema, chylothorax, or other chylous fluid collections that may be difficult to diagnose and treat without adequate evaluation of the associated lymphatic anatomy. Assessment of this anatomy by direct contrast injection has typically been limited to the extremities, as in procedures such as sentinel node mapping or intradermal lymphoscintigraphy. These methods do not adequately opacify larger, central lymphatics such as the thoracic duct or cisterna chyli; however, and alternative imaging modalities such as routine T2-weighted magnetic resonance (MR) imaging fail to capture information regarding dynamic flow. In the current study, a temporally-sequenced MR-based imaging technique was used to evaluate the central lymphatic vascular tree in a small series of patients with symptoms concerning for lymphatic disease. The technique successfully visualized the relevant lymphatic structures in all evaluated subjects and allowed for appropriate management steps to be undertaken in each case. The study was limited by its small sample size and lack of a reference standard. Procedurally, the technique was limited by its labor-intensive and invasive requirements, such as the need for endotracheal intubation to achieve adequate breath holding during image acquisition. Future studies directly comparing T2-weighted lymphatic MR imaging to contrast-enhanced MRL are needed to better assess the added value of this new technique.
In-Depth [retrospective case series]: Six consecutive patients with a clinical indication for central conducting lymphatic imaging were retrospectively selected for evaluation after undergoing dynamic T1-weighted MRL with gadolinium-based contrast. Gadopentetate dimeglumine was infused into the medulla of inguinal lymph nodes at a concentration of 0.2mmol/kg by direct cannulation. All patients required intubation, sedation, and mechanical ventilation to facilitate breath holding for adequate image acquisition. Images were acquired every 30-60 seconds as the contrast traveled through the retroperitoneal lymphatics into the cisterna chyli and thoracic duct. This process was technically successful in all patients, and all associated MR images were of diagnostic quality. Overall, MRL positively identified lymphatic disease in 4 of 6 patients and excluded lymphatic disease in the remaining 2 patients. Clinically, MRL changed management for 2 patients in whom previously-unknown lymphatic dysplasia was diagnosed, while conservative management was subsequently pursued for 3 patients in whom normal anatomy, chylolymphatic reflux, or expected post-surgical changes were identified. The final patient was revealed to be suffering from non-lymphatic pathology. No adverse events were identified in this study.
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