b'lymphatic system, the thoracic duct, and theThis classification is based on the clinical features,connection with the venous system 5 . This is particularlythe localization of the edema, and the associated useful in those living with a complex lymphaticphenotype. According to it, primary lymphedemaanomaly, who often have both increased lymphaticis divided into five groups: flow and aberrant anatomy 39 . DCMRL can also1) Syndromes demonstrate focal areas of lymphatic leakage inthe chest or abdominal cavities, responsible for2) L ymphedema with systemic or visceral chylous ascites, chylous pleural effusions, and involvementchylous pericardial effusions 40 . This information can3)Lymphedema with a congenital onsetthen be used for pre-procedure guidance for planned(1.0 year) embolization or lymphovenous bypasses 41 . DCMRL4) Lymphedema with a late onset (1.0 year)also confers the advantage of visualizing lymphatic5) Vascular and lymphatic malformationsmasses, chylous effusions, lymphatic malformations, and associated visceral or bony lesions without aOverall, this classification has the objective of second examination. Of note, some centers haveproviding an accurate diagnosis, as well as facilitating begun to utilize CT lymphangiography in lieu of research into the genetic causes of the different MR, which allows excellent anatomic imaging but phenotypes. does not provide the same dynamic imaging ofDetailed Information on the Diagnosis of:lymphatic flow 42 .Conventional Lymphangiography: Intra-nodalPrimary Lymphedemalymphangiogram with water-soluble contrast andDiagnosis of primary lymphedema can be challenging, oil-based contrast is typically performed before andand some individuals remain undiagnosed for years.during interventions. Water-soluble contrast is difficultIt is important to receive a correct diagnosis asto visualize under fluoroscopy and is typically reservedsoon as possible after the appearance of the for infants. Oil-based contrast can be visualized undersymptoms, in order to consider concomitant medical live fluoroscopy and can identify the anatomy andconditions, facilitate treatment, and reduce thefunction of the lymphatic system, similar to MRrisk of progression 20 . An accurate diagnosis and lymphangiography. Oil-based contrast also has aunderstanding of the cause of lymphedema are higher viscosity and, therefore, remains within theimportant for the implementation of optimal patient lymphatic system for a longer period. The cisterna care and management 48 . chyli remains radio-opaque and can be targeted andWe recommend the following criteria for referral tocan be calculated with a microcatheter for intervention.an expert center (see Figure 5): Patients with edema The same contrast agents have more recently beenfor more than three months in combination with oneinjected into the hepatic and mesenteric lymphatics.of the following: Congenital debut, family historyThe hepatic lymphatics are in the peri-portal space of swelling, genital swelling, systemic involvementand can be visualized with injection of water-soluble(e.g., intestinal lymphangiectasia, pleural effusions, contrast or a small amount of lipiodol. This can beetc.), syndromic forms, recurrent cellulitis.another route to visualize the thoracic duct or identifyIn the expert center, a more detailed patient history a lymphatic leak 43 . Mesenteric lymphangiography isshould focus on age of onset, family history, and performed by inserting a needle into the mesentericsymptoms (e.g., pain, functional/psychologicallymph nodes in the mesentery surrounding the impact, heaviness). It is, moreover, essential tobowel. Lipiodol is then injected and can be used have information about previous surgical historyto demonstrate mesenteric lymphatic outflow,(e.g., lymphadenectomy, injury, or trauma) andobstruction, or leakage 44 . medical history (e.g., cellulitis/erysipelas, cancer, DIAGNOSIS OF PRIMARY LYMPHEDEMA radiation therapy). Author: Vaughan Keeley, MD Physical examination must include weight, size, and The term primary lymphedema covers a group BMI, while in children, a height-weight curve andof rare genetic conditions that lead to abnormalhead circumference should be done. Moreover, the functioning and/or development of the lymphaticexamination should investigate the degree and stage system 20 . It represents a heterogeneous group of oedema in different body parts (e.g., legs, arms, genitalia, face) and inspect whether the edema is that includes sporadic, hereditary, and syndromic symmetrically distributed 49 .forms. The first classification algorithm for primary lymphatic diseases was the St. Georges ClassificationLymphedema patients may develop skin problems Algorithm of Primary Lymphatic Anomalies, developedsuch as warts, vesicles, papillomatosis, nail in 2010 45and further updated in 2013 and 2020 46,47 .abnormalities (up-slanting toenails), and bacterial| Standardized Approach for the Diagnosis and Management of Lymphedema (LE) and Lymphatic Diseases (LD)|14'