Intravenous MR Lymphangiography Exploits 'Lymphatic Phase' to Image Hepatic and Mesenteric Lymphatics

IV contrast-enhanced MR lymphangiography (IV-MRL) captures a 'lymphatic phase' peaking 20–30 min post-injection; in a pilot of 16 patients, thoracic duct-to-IVC signal intensity ratio rose from 0.49±0.21 at 1 min to 1.47±0.32 at 20 min (p<.001).

• Swine (n=2) lymph sampling and pilot human study (n=16, mean age 56.6 y, 11 men); gadolinium concentration in lymph exceeded that in portal/systemic veins at 20–30 min, defining the 'lymphatic phase'.
• Thoracic duct-to-IVC signal ratio increased significantly from 1 min to 20 min (0.49±0.21 → 1.47±0.32, p<.001); hepatic and mesenteric lymphatics enhanced in swine during this phase.
• Limitations: small sample, single-center, no formal comparison with invasive dynamic contrast-enhanced MR lymphangiography (DCMRL) in patients.

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