Is the Liver Part of the Lymphatic System?
Yes, the liver is intimately connected to the lymphatic system and is actually the largest lymph-producing organ in the body, generating 25-50% of all lymph that flows through the thoracic duct. 1, 2, 3
The Liver's Role in Lymph Production
The liver produces more lymph than any other organ in the body:
Between 25% and 50% of all lymph received by the thoracic duct originates from the liver, making it the single largest contributor to total body lymph production 2, 3
Hepatic lymph primarily originates from the hepatic sinusoids, where fluid is filtered out of the sinusoidal blood into the space of Disse 3
Fluid from the space of Disse flows through channels with collagen fibers that traverse the limiting plate, connecting to the interstitial space in portal tracts or around sublobular veins 3
Anatomical Organization of Hepatic Lymphatics
The hepatic lymphatic system is organized into distinct anatomical compartments:
Deep Lymphatic System
- Portal lymphatic vessels that follow the portal tracts and drain approximately 80% or more of hepatic lymph 3
- Sublobular lymphatic vessels that follow the hepatic veins 2, 3
Superficial Lymphatic System
Capsular lymphatic vessels located in the liver capsule on both the convex and inferior surfaces 2, 3
There are no direct communications between the liver parenchyma and the first lymphatic capillaries, which end blindly in the surrounding connective tissue 4
Clinical Significance in Liver Disease
The hepatic lymphatic system plays crucial roles in various pathological conditions:
Lymphangiogenesis (growth of new lymphatic vessels) occurs in cirrhosis, viral hepatitis, and hepatocellular carcinoma 1
Intrahepatic MR lymphangiography can now image liver lymphatics and has revealed abnormal lymphatic patterns that correlate with symptoms such as chylothorax 5
Hepatic venous congestion leads to sinusoidal dilatation, hyperfiltration, and increased lymph production, with compensatory hepatic lymphangiogenesis occurring in response 6
The area of portal lymphatic vessels increases in liver fibrosis, cirrhosis, and idiopathic portal hypertension 3
Lymphatic vessels are abundant in the immediate vicinity of hepatocellular carcinoma and liver metastases, with lymphangiogenesis associated with enhanced metastasis 3
Common Pitfall to Avoid
While the liver is not traditionally classified as a "lymphoid organ" like lymph nodes or the spleen (which are part of the immune system's lymphatic tissue), it is definitively part of the lymphatic vascular system as the body's largest lymph producer. This distinction is important: the liver contains an extensive lymphatic vascular network but is not itself composed of lymphoid tissue 1, 2.