ABSTRACT
Lower extremity swelling may be broadly characterized as due to edema, lymphedema, or lipedema. Differentiation between these three conditions is important for providing appropriate treatment. This review analyzes and compares different clinical diagnostic modalities for these conditions, with the aim of assisting in the process of choosing the most appropriate diagnostic modality by highlighting the advantages and limitations of each. Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines for a systematic search of peer-reviewed literature, the following diagnostic methods for lower extremity swelling were investigated: (1) ultrasound (US), (2) lymphoscintigraphy (LSG), (3) computed tomography (CT), (4) bioimpedance spectroscopy (BIS), (5) tissue dielectric constant (TDC), and (6) magnetic resonance imaging (MRI), including magnetic resonance lymphangiography (MRL). The databases used in the search were PubMed, ProQuest, CINAHL Complete, Web of Science, Embase, and Biomedical Reference Collection. After retrieving 115 studies based on predetermined inclusion criteria, a total of 31 studies were critically evaluated. The main results indicate the following: duplex US is the modality of choice to initially identify lower extremity edema such as deep venous thrombosis (DVT) and venous reflux due to its high sensitivity and specificity. CT venography of the lower extremity appears to bethe preferred option for gynecologic cancer patients with lower extremity swelling post-treatment, as it measures subcutaneous tissue volumes to look for DVTs, lymphoceles, and cancer recurrence. TDC is a recommended modality for a variety of conditions, including edema and lymphedema, in part, due to its noninvasive localized assessment capabilities and ease of use. LSG emerges as an effective imaging modality for lymphedema characterization with minimal invasiveness and high sensitivity and specificity. BIS is widely used to identify and monitor lower extremity lymphedema but has been reported to have low sensitivity and lacks the ability to account for changes in tissue composition such as fibrosis. US and MRL are favored for lipedema diagnosis, with MRL providing comprehensive anatomical and functional insights, albeit with cost and accessibility limitations compared to US. While CT, MRI, US, and TDC are all useful for differentiating lymphedema from lipedema, MRI is the preferred modality due to its anatomical and functional diagnostic capabilities. However, US is a pragmatic alternative for use with obese patients or when MRI is not an option.
