Malignant tumor cells are often caught and spread from peripheral satellite nodes. The lymphatic system returns proteins from the interstitial fluid of the liver and intestine to the blood vascular system , helps to maintain the renal concentrating ability, and transports in lipoproteins , fats, long-chain fatty acids and cholesterol absorbed in the intestine. The lymphatics are necessary for the maintenance of normal tissue fluid levels. Edema Obstruction of the lymphatics can cause regional accumulation of fluid known as edema. Edema is harmful because the delivery of nutrients and removal of wastes is impeded by increased tissue fluid pressures and diffusion distances.
Gravity contributes to edema in dependent parts as does the retention of salt in the body.
Certain parasites have a preference for the lymphatics and can cause edema via the obstruction of the lymph capillaries. Another cause of obstruction is metastatic infiltration and obstruction of the lymph nodes and vessels. High blood pressures or increases in capillary permeability also can precipitate edema. The causes of edema are classified as lymphangitis when the lymph vessels are inflamed due to bacterial infection most commonly by streptococci, lymphadenitis when lymph nodes are inflamed, and lymphadema when the edema results from obstruction.