Abstract

Appropriate diagnosis, staging and a further selection of the best treatment are fundamental for the management of patients with extremity lymphedema. Several clinical and imaging tools have been described for these purposes. Lymphoscintigraphy is still considered the gold standard imaging modality for diagnosing lymphedema. However, protocol variability and poor image resolution can make the interpretation challenging. Here, we reviewed technical aspects of lymphoscintigraphy, interpretation of the lymphoscintigraphy findings, staging, and its clinical application.

Main findings

• The main criticism against lymphoscintigraphy is the lack of a standardized protocol regarding the radiotracer administrated, the type of injection, the dynamic or static acquisitions, the acquisition times and the evaluation in rest or after exercise, resulting in heterogeneous results from different centres.
• Lymphoscintigraphy provides both qualitative and quantitative analyses. Qualitative lymphoscintigraphy primarily aims to demonstrate the morphology of the lymphatic system visualizing the lymph nodes and lymphatic ducts.
• Common findings of the lymphatic system demonstrated by qualitative lymphoscintigraphy include the symmetry and intensity of uptake, number and timing of appearance of proximal lymph nodes, the number and course of lymphatic ducts, collateral lymphatics, the presence and location of dermal backflow, the presence of abnormal deep collateral flow such as antecubital or popliteal lymph nodes. Dermal backflow is considered an abnormal displacement of lymph from lymphatic ducts to the surface of the limb. This finding may be due to an unfavourable gradient pressure, together with local incompetence of lymphatic valves, resulting in the abnormal passage of lymph toward the dermis.
• If untreated, with long symptom duration, dermal backflow can extend to the entire limb, resulting in a progressive limb swelling.
• Quantitative lymphoscintigraphy aims to measure lymphatic flow and may be a more sensitive method for diagnosing the lymphatic obstruction. However, quantitative lymphoscintigraphy analyses often showed inconsistent results and, they are time-consuming.
• There is no evidence in previous studies if lymphoscintigraphy is able to differentiate between primary and secondary lymphedema.
• The poor imaging quality depends on the selection of an appropriate radiotracer or due to technical issues.
• The authors recently developed a new lymphoscintigraphy staging named TLS to help the clinician in the diagnosis and assessment of lymphedema in everyday practice.30 On the basis of the presence of three major lymphoscintigraphy findings (1) visualization of proximal/intermediate lymph nodes, (2) linear lymphatic ducts, and (3) dermal backflow, lymphoscintigraphy were classified into three patterns further divided into seven stages.
• Lymphoscintigraphy is a reliable diagnostic tool for investigating the lymphatic system. Standardized lymphoscintigraphy protocol including radiotracer, dose, injection and image‐captured time are the key factors to achieve good lymphoscintigraphy images for the diagnosis of lymphedema. TLS is a useful tool for assessing the severity of lymphedema and could provide additional information to guide the surgical treatment and evaluate the treatment outcome.