Lymphovenous shunts: from development to clinical applications

Abstract

The lymphatic system is a vast network of vessels that functions to return excess fluid from the interstitial space to the blood stream. 1 Excess interstitial fluid is drained by lymphatic capillaries, which are composed of a single layer of lymphatic endothelial cells that overlap with each other. The overlapping cells are thought to act as primary valves allowing flow of interstitial fluid into lymphatic vessels but limiting outflow. [2][3][4] Lymph then flows from these capillaries into collecting lymphatics 5 which have a layer of lymphatic muscle cells (LMCs) that work to transport lymph through rhythmic contraction. 6,7 This intrinsic force from LMCs occurs in conjunction with extrinsic compressive force from surrounding tissue to propel lymph through the lymphatic system. 6,8 A secondary system of intraluminal valves within the lymphatic collecting ducts themselves prevents backflow of lymphatic fluid toward the capillaries. 6,8,9 Lymph then travels through lymph nodes into post-nodal lymphatic ducts which converge into either the thoracic duct or the right lymphatic duct; these are classically described as emptying into the junction of the subclavian veins and internal jugular veins on the left and right side, respectively. 9,10 These connections are the body's two major anatomic lymphovenous shunts, a term which refers to the anastomoses, be it natural or surgical, between the lymphatic system and the venous system. 11 | ANATOMIC ALLY NORMAL LYMPHOVENOUS S HUNTS | Thoracic duct and right lymphatic ductThe natural anastomosis between the thoracic duct and the subclavian vein represents a well-known anatomic lymphovenous shunt. 12 The thoracic duct (TD) most commonly originates from the cisterna

The Microvascular-Lymphatic Interface and Tissue Homeostasis: Critical Questions That Challenge Current Understanding

“…The collecting lymphatics connect to lymph nodes and coalesce into larger lymph trunks. A significant portion of both water and innate immune cells found in prenodal lymph is returned to the circulatory system at lymph nodes where there is significant aquaporin-1 expression on both lymphatic and blood endothelial cells [31][32][33][34][35][36]. The remaining post-nodal lymph is returned to the circulation by the larger trunks, namely, the thoracic duct and the right lymph duct.…”

“…Because of this slow manifestation, many associated pathologic factors, such as long-term inflammation and tissue remodeling, including fibrosis, can develop prior to intervention [42]. Treatment is typically limited to compression therapy, although there have been some recent clinical trials with anti-inflammatory therapies and surgical interventions [34, 43]. Thus, lymphedema is a complex disease which in addition to the impairment of the lymphatic vessels themselves includes impaired oxygen delivery due to greater diffusion distances, inflammation, changes in tissue architecture, and an altered physiological state of the interstitial fluid pressure gradients including elevated resistance to fluid flow [42, 44].…”

“…Redundancy in lymphatic networks prior to reaching outflow points is apparently protective against formation of breast cancer-related secondary lymphedema for people who have significant lymph drainage of the lateral arm through the Mascagni-Sappey pathway that bypasses the axillary lymph nodes [133]. The ongoing development of lymph node transplants as emerging therapy for lymphedema [34], and new tools for visualizing lymphatic flow in the surgical setting [134] offer promise for alleviating the bottleneck effect of damaged lymph trunks or lymph nodes that can significantly impair entire networks.…”

Lymphovenous shunts in the treatment of lymphedema

“…They can be classified as physiological, pathological, or iatrogenic/surgical based on their etiology. 2 Physiological LVSs exist in individuals with normal lymphatics. The anastomoses between the thoracic duct and the subclavian vein represent well-known LVSs.…”

“…They can be classified as physiological, pathological, or iatrogenic/surgical based on their etiology. 2…”