Indocyanine Green (ICG) Lymphography

Abstract

Primary lymphedema is caused by various lymphatic malformations and has a wide variety of etiology. Lymphatic image is important to understand underlying pathophysiology of primary lymphedema. Indocyanine green (ICG) lymphography allows very clear superficial lymph flow visualization in real time, which can be performed less invasively without radiation exposure. With progression of lymphedema, ICG lymphography finding changes from linear pattern to splash, to stardust, and finally to diffuse pattern. Different ICG lymphography pattern represents different lymphatic vessel conditions; lymphatic vessel becomes more sclerotic with progression of ICG lymphography findings. Primary lymphedema can be classified into four patterns based on ICG lymphography findings; proximal dermal backflow (PDB), distal dermal backflow (DDB), less enhancement (LE), and no enhancement (NE) patterns. In PDB and DDB patterns, lymph flow obstruction is a main cause of lymphedema, and lymphatic bypass operation can be a useful therapeutic option for compression-refractory lymphedema. In LE pattern, non-obstructive mechanism such as lymph pump dysfunction is considered a cause of lymphedema, and strict compression therapy is recommended. In NE pattern, whole limb severe hypoplasia or aplasia is suspected, and vascularized lymph node transfer may be better indicated than lymphatic bypass operation. ICG lymphography is useful not only for lymphedema evaluation but also for navigation of lymphatic surgery.