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Lymphoscintigraphy Interpretation, Staging, and Lymphedema Grading


Key Points

  • Lymphoscintigraphy is an objective and reliable imaging modality for diagnosing lymphedema, categorizing its severity, and guiding appropriate treatment.

  • The diagnostic utility of lymphoscintigraphy depends upon meticulous technical performance and correct image interpretation.

  • The main drawback of lymphoscintigraphy is the lack of standardized protocols, making comparisons among the studies difficult.

  • Several lymphoscintigraphic staging or scoring systems have been proposed, with variable clinical applications. The recently validated Taiwan Lymphoscintigraphy Staging (TLS) system includes the most relevant lymphoscintigraphy findings grouped by severity, providing an easy tool for the diagnosis and severity categorization of lymphatic obstruction.

  • The Cheng Lymphedema Grading system, combined with additional TLS information, is a promising lymphedema grading system for patient selection regarding surgical treatments.

Disclosures : Ming-Huei Cheng received textbook royalties from Elsevier, Inc.

Introduction

Extremity lymphedema represents a chronic debilitating disease with a high tendency to progress, which may increase physical disability and recurrent cellulitis in the advanced stages without adequate treatment. The progression of lymphedema can lead to significant decreases in overall patient-reported quality of life outcomes, with significant physical and visual discomfort. With the increasing availability of lymphedema treatments and awareness of the problem, early recognition and diagnosis are now possible for reducing the morbidity and for the successful treatment of these patients. Extremity lymphedema is usually diagnosed through history and physical examination. However, diagnosis and severity determination can be a challenge for the physician in an attempt to find and start an effective treatment. A number of imaging modalities can be used to aid in the diagnosis of lymphedema. Lymphoscintigraphy was first introduced in 1950 and has become, for many years, the benchmark procedure for the diagnosis of lymphedema with the ability to visualize the functional status of the lymphatic system. The procedure is minimally invasive, easy to perform, and safe as radiotracers rarely cause an allergic reaction. It involves the injection of a protein or colloid with a radioactive technetium-99m ( 99m Tc)-labeled tracer into the web spaces of the fingers or toes. Then, the radiotracer is taken up by the lymphatic system through the lymphatics, the collectors, and transported to the proximal limb of the inguinal or axillary lymph nodes. This nuclear medicine procedure is able to visualize proximal lymph node uptake, visualize superficial and deep lymphatic vessels, and detect abnormal lymphatic findings. The main limitation of lymphoscintigraphy is the lack of a standardized protocol and the occasional poor image resolution. Hence, making comparisons between lymphoscintigraphic studies in the literature is confounded by the variety of protocols with heterogeneous results and conclusions.

The use of lymphoscintigraphy varies worldwide. Although in some centers, it is performed for almost all patients with suspected lymphedema as a routine part of the diagnosis, in others, it is rarely applied, mainly due to unfamiliarity with the interpretation of this imaging modality.

Several lymphoscintigraphic staging or scoring systems have been proposed in the literature, with variable applications in clinical practice. The recently validated Taiwan Lymphoscintigraphy Staging (TLS) system is correlated with objective clinical findings and has been developed to provide an easy tool for diagnosis, categorization of lymphatic obstruction severity, and selection of appropriate treatment in extremity lymphedema patients.

This chapter focuses on the clinical application and interpretation of lymphoscintigraphy for the diagnosis and severity determination of extremity lymphedema, patient selection for appropriate treatments, and the evaluation of treatment outcome.

Diagnosis and Severity of Lymphedema: Clinical and Lymphoscintigraphy Findings

Diagnosis of Lymphedema

Patients with limb swelling are often commonly described with the term lymphedema regardless of the underlying cause. However, lymphedema, which may be primary or secondary, is a unique disease with specific clinical and imaging findings. Nonetheless, 25% of patients referred to a lymphedema service with the diagnosis of “lymphedema” have another disease.

The differential diagnosis of lymphedema is broad, which includes obesity, lipedema, infection, primary/recurrent malignancy, vascular anomalies, and systemic diseases such as congestive heart failure, hepatic failure, renal failure, hypoproteinemia, electrolyte imbalances, and peripheral neuropathies. The astute clinician should be able to accurately diagnose extremity swelling among multiple etiologies. Providing a correct diagnosis of the limb swelling is key before starting a treatment plan and establishing an objective baseline.

A thorough history and physical examination are the essential first steps to establishing a correct diagnosis of lymphedema. In most cases, the causes of primary and secondary lymphedema can be easily identified in the patient’s history. The clinical presentation is characterized by limb heaviness, swelling, tissue thickening, paresthesia, and recurrent cellulitis accompanied occasionally by localized pain. Initially, pitting edema is present in the distal limb and changes to non-pitting edema with the progression of the disease due to the collection of subcutaneous adipose and fibrosis. The Stemmer sign is commonly used for the clinical diagnosis of lymphedema. Noticeably, these clinical findings could result from a variety of diseases, and the diagnosis of lymphedema is not always correct.

Simultaneous assessment of the venous and lymphatic system is essential for a precise diagnosis. Duplex ultrasonography should be performed first in all forms of lymphedema to differentiate between lymphatic and venous etiologic factors or for the diagnosis of concomitant vascular anomalies. In the senior author’s routine practice, computed tomography (CT) angiography is used to diagnose vascular lesions if there is a suspicious clinical examination finding (e.g., cutaneous evidence of hemangioma, vascular malformation, or a palpable thrill).

Since 2018, in our lymphedema center, single photon emission computed tomography (SPECT) and magnetic resonance imaging (MRI) have been added for the diagnosis of chylous ascites secondary to retroperitoneal lymphangiomatosis.

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