Magnetic resonance imaging versus lymphoscintigraphy for the assessment of focal lymphatic transport disorders of the lower limb: first experiences

Current and Developing Lymphatic Imaging Approaches for Elucidation of Functional Mechanisms and Disease Progression

Study of the lymphatic system, compared to that of the other body systems, has been historically neglected. While scientists and clinicians have, in recent decades, gained a better appreciation of the functionality of the lymphatics as well as their role in associated diseases (and consequently investigated these topics further in their experimental work), there is still much left to be understood of the lymphatic system. In this review article, we discuss the role lymphatic imaging techniques have played in this recent series of advancements and how new imaging techniques can help bolster this wave of discovery. We specifically highlight the use of lymphatic imaging techniques in understanding the fundamental anatomy and physiology of the lymphatic system; investigating the development of lymphatic vasculature (using techniques such as intravital microscopy); diagnosing, staging, and treating lymphedema and cancer; and its role in other disease states.

Management of Lipedema Beyond Liposuction: A Case Study

Lipedema is a pathologic accumulation of adipose tissue in the subcutaneous layer of the extremities. This connective tissue disorder, which predominately affects females, is often misdiagnosed despite an incidence of ∼11%. Misdiagnosis often leads to delays in appropriate treatment, further increasing the morbidity of the condition. The authors report their facilities' experience in treating a patient with lipedema, requiring multiple surgical interventions involving liposuction and skin debulking to achieve desired aesthetic outcomes. The patient presented to the plastic surgery clinic with severe lipedema of the bilateral lower extremities. She previously underwent a panniculectomy and bilateral lower extremity liposuction without achieving the desired aesthetic results. Prior conservative management and liposuction alone were both unsuccessful treatment options and she required debulking procedures, along with further liposuction, as definitive management. The patient underwent 2 procedures at the clinic, both consisting of liposuction and panniculectomy of the lower extremities and buttocks. The procedures were conducted 1 year apart but were able to achieve the patient's desired aesthetics goals. Management of lipedema can be challenging, but not impossible. This case report shows that local excision is a viable option for treatment if minimally invasive options yield limited results.

Level of Evidence 5

Imaging of the Lymphatic Vessels for Surgical Planning: A Systematic Review

BACKGROUND

Secondary lymphedema is a common complication after surgical or radiotherapeutic cancer treatment. (Micro) surgical intervention such as lymphovenous bypass and vascularized lymph node transfer is a possible solution in patients who are refractory to conventional treatment. Adequate imaging is needed to identify functional lymphatic vessels and nearby veins for surgical planning.

METHODS

A systematic literature search of the Embase, MEDLINE ALL via Ovid, Web of Science Core Collection and Cochrane CENTRAL Register of Trials databases was conducted in February 2022. Studies reporting on lymphatic vessel detection in healthy subjects or secondary lymphedema of the limbs or head and neck were analyzed.

RESULTS

Overall, 129 lymphatic vessel imaging studies were included, and six imaging modalities were identified. The aim of the studies was diagnosis, severity staging, and/or surgical planning.

CONCLUSION

Due to its utility in surgical planning, near-infrared fluorescence lymphangiography (NIRF-L) has gained prominence in recent years relative to lymphoscintigraphy, the current gold standard for diagnosis and severity staging. Magnetic resonance lymphography (MRL) gives three-dimensional detailed information on the location of both lymphatic vessels and veins and the extent of fat hypertrophy; however, MRL is less practical for routine presurgical implementation due to its limited availability and high cost. High frequency ultrasound imaging can provide high resolution imaging of lymphatic vessels but is highly operator-dependent and accurate identification of lymphatic vessels is difficult. Finally, photoacoustic imaging (PAI) is a novel technique for visualization of functional lymphatic vessels and veins. More evidence is needed to evaluate the utility of PAI in surgical planning.

A Systematic Review Comparing Lymphoscintigraphy and Magnetic Resonance Imaging Techniques in the Assessment of Peripheral Lymphedema

BACKGROUND

Peripheral lymphedema represents a debilitating condition affecting the lymphatic system of the limbs resulting from impaired drainage and excessive lymphatic fluid accumulation in the interstitial spaces. Lymphoscintigraphy is the imaging modality of first choice to investigate patients with peripheral lymphedema. Nevertheless, in recent times, magnetic resonance imaging (MRI) techniques have also been applied to assess patients with lymphedema.

OBJECTIVE

The present systematic review aims to appraise the evidence by providing a head-to-head comparison between lymphoscintigraphy and MRI techniques in peripheral lymphedema.

METHODS

A systematic literature search was performed using the PubMed database and Cochrane Central Register of Controlled Trials (CENTRAL). The eligibility criteria for the articles to be included in the qualitative synthesis were: 1) a study cohort or a subset of patients with a clinical diagnosis of peripheral lymphedema (either upper or lower limb); 2) execution of both MR imaging and lymphoscintigraphy in the same subset of patients. The methodological quality of the studies was assessed by an investigator using the "Quality Assessment of Diagnostic Accuracy Studies" tool, v. 2 (QUADAS-2).

RESULTS

Overall, 11 studies were ultimately included in the quantitative analysis. No meta-analysis was performed due to the heterogeneous patient samples, the different study aims of the retrieved literature, and the limited number of available articles. In the diagnosis of upper limb extremity lymphedema, the sensitivity of MRI techniques appears superior to that of lymphoscintigraphy. Comparative studies in the lower limbs are still scarce but suggest that MRI may increase the diagnostic accuracy for lymphedema.

CONCLUSION

The available literature on patients with lymphedema evaluated with both lymphoscintigraphy and MRI does not allow definite conclusions on the superiority of one imaging technique over the other. Further studies, including well-selected patient samples, are still necessary to compare the accuracy of these imaging modalities. Since MRI techniques seem to provide complementary findings to lymphoscintigraphy, it would be conceivable to acquire both imaging exams in patients with peripheral lymphedema. Furthermore, studies evaluating the clinical impact of adding MRl to the diagnostic workup are warranted.

Lymphoedema praecox in a young woman: a rare disease

Primary lymphoedema is a rare disorder. Often presents at a young age with asymptomatic limb oedema with gradual progression. We present a 16-year-old woman who presented with a history of swelling of the left lower limb for 6 years. There was the presence of isolated left lower limb oedema, which was a non-pitting type. The patient underwent imaging studies and was diagnosed to have primary lymphoedema. The patient was managed conservatively as the patient did not have any other problems other than the left lower limb oedema.

Visualization of Both the Superficial and Deep Lymphatic System of the Upper Extremity Using Magnetic Resonance Lymphography

Background: The lymphatic system consists of the superficial and deep lymphatic system. Several diagnostic methods are used to assess the lymphatic system. Lymphoscintigraphy and indocyanine green lymphography are widely applied, both showing disadvantages, such as a poor resolution and lack of field of view. Magnetic resonance lymphography (MRL) shows satisfactory temporal and spatial resolution. The aim of this study was to assess both the superficial and deep lymphatic system in the upper extremity of healthy subjects, using an MRL protocol. Methods and Results: Ten healthy volunteers underwent an MRL examination, using a three Tesla MRI unit. Water-soluble gadolinium was used as a contrast agent. MRL images were evaluated by an experienced radiologist on image quality, enhancement of veins and lymphatic vessels, and characteristics of the latter. Overall image quality was good to excellent. In all subjects, veins and lymphatic vessels could be distinguished. Superficial and deep lymphatic vessels were seen in 9 out of 10 subjects. Lymphatic vessels with a diameter between 0.9 and 4.3 mm were measured. Both veins and lymphatic vessels showed their characteristic appearance. Enhancement of veins was seen directly after contrast agent injection, which decreased over time. Lymphatic vessel enhancement slowly increased over time. Mean total MRL examination (room) time was 110 minutes (81 minutes scan time). Conclusions: The MRL protocol accurately visualizes both deep and superficial lymphatic vessels showing their characteristic appearances with high spatial resolution, indicating the MRL can be of value in diagnosing and staging peripheral lymphedema.

Value of one additional injection at the root of the limb in the lymphoscintigraphic evaluation and management of primary and secondary lower-limb lymphedemas

Introduction

The classical lymphoscintigraphic investigations of lower-limb lymphatic edema [LLLE] sometimes reveal either no or few lymph nodes [LNs] at the root of the limb[s] and/or in the abdomen. The aim of the present paper is to report the results of performing one additional injection at the root of the edematous limb[s] to force the visualization of the LNs and/or to demonstrate the collateral lymphatic pathways in such patients.

Methods and findings

We retrospectively reviewed our database and found 99 patients [44 primary LLLE with 47 limbs injected and 55 with LLLE secondary to treatments for cancer with 64 limbs injected] where such an additional injection had been performed.

In the 43 LLLE patients where no LNs were seen at the end of the classical exam [15 primary LLLE and 28 secondary LLLE], the extra injection showed lymphatic drainage toward LN[s] in all except 3 and when at least one LN was seen, the injection showed lymphatic drainage in every case toward the same ipsilateral [inguinal and/or iliac] LNs [as shown by the classical injection] and/or toward additional LNs.

In 40.7% of patients, we observed one or more additional lymphatic pathways: prepubic superficial lymphatic vessels [LV] crossing the midline anteriorly toward contralateral inguinal LNs in 21 [18.9%], “posterior” LV [toward contralateral inguinal LNs and/or ipsi- or contralateral lumbo-aortic and/or para-renal LNs] in 14 [12.6%], but deep LV toward the ipsilateral common iliac LNs passing between the gluteal muscles in 32 [28.8%].

Conclusion

Our work pinpoints one limitation of classical bipedal radionuclide lymphangiography. In patients with primary and secondary LLLE where inguinal and/or iliac LNs cannot be seen on bipedal radionuclide lymphangiography, this additional injection reveals the true lympho-nodal status and shows unexpected collateral lymphatic pathways in 40% of cases. Such information is of the utmost importance in LLLE management and its acquisition is consequently recommended in these patients.

Systematic Review of Magnetic Resonance Lymphangiography From a Technical Perspective

BACKGROUND

Clinical examination and lymphoscintigraphy are the current standard for investigating lymphatic function. Magnetic resonance imaging (MRI) facilitates three-dimensional (3D), nonionizing imaging of the lymphatic vasculature, including functional assessments of lymphatic flow, and may improve diagnosis and treatment planning in disease states such as lymphedema.

PURPOSE

To summarize the role of MRI as a noninvasive technique to assess lymphatic drainage and highlight areas in need of further study.

STUDY TYPE

Systematic review.

POPULATION

In October 2019, a systematic literature search (PubMed) was performed to identify articles on magnetic resonance lymphangiography (MRL).

FIELD STRENGTH/SEQUENCE

No field strength or sequence restrictions.

ASSESSMENT

Article quality assessment was conducted using a bespoke protocol, designed with heavy reliance on the National Institutes of Health quality assessment tool for case series studies and Downs and Blacks quality checklist for health care intervention studies.

STATISTICAL TESTS

The results of the original research articles are summarized.

RESULTS

From 612 identified articles, 43 articles were included and their protocols and results summarized. Field strength was 1.5 or 3.0 T in all studies, with 25/43 (58%) employing 3.0 T imaging. Most commonly, imaging of the peripheries, upper and lower limbs including the pelvis (32/43, 74%), and the trunk (10/43, 23%) is performed, including two studies covering both regions. Imaging protocols were heterogenous; however, T2 -weighted and contrast-enhanced T1 -weighted images are routinely acquired and demonstrate the lymphatic vasculature. Edema, vessel, quantity and morphology, and contrast uptake characteristics are commonly reported indicators of lymphatic dysfunction.

DATA CONCLUSION

MRL is uniquely placed to yield large field of view, qualitative and quantitative, 3D imaging of the lymphatic vasculature. Despite study heterogeneity, consensus is emerging regarding MRL protocol design. MRL has the potential to dramatically improve understanding of the lymphatics and detect disease, but further optimization, and research into the influence of study protocol differences, is required before this is fully realized.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY: Stage 2.

A systematic review of magnetic resonance lymphography for the evaluation of peripheral lymphedema

OBJECTIVE

Visualization of the lymphatic system is necessary for both early diagnosis and associated treatments. A promising imaging modality is magnetic resonance lymphography (MRL). The aim of this review was to summarize different MRL protocols, to assess the clinical value in patients with peripheral lymphedema, and to define minimal requirements necessary for visualization of lymphatics.

METHODS

A systematic literature search was conducted in PubMed, Embase, and the Cochrane Library in December 2018. Studies performing MRL in patients with peripheral lymphedema or healthy participants were included. Study design, population, etiology, duration of lymphedema, clinical staging, contrast agent, dose, injection site, and technical magnetic resonance imaging details were analyzed. No meta-analyses were performed because of different study aims and heterogeneity of the study populations.

RESULTS

Twenty-five studies involving 1609 patients with both primary lymphedema (n = 669) and secondary lymphedema (n = 657) were included. Upper and lower limbs were examined in 296 and 602 patients, respectively. Twenty-two studies used a gadolinium-based contrast agent that was injected intracutaneously or subcutaneously in the interdigital web spaces. Contrast-enhanced T1-weighted combined with T2-weighted protocols were most frequently used. T1-weighted images showed lymphatics in 63.3% to 100%, even in vessels with a diameter of ≥0.5 mm. Dermal backflow and a honeycomb pattern were clearly recognized.

CONCLUSIONS

MRL identifies superficial lymphatic vessels with a diameter of ≥0.5 mm with high sensitivity and specificity and accurately shows abnormal lymphatics and lymphatic drainage patterns. Therefore, MRL could be of clinical value in both early and advanced stages of peripheral lymphedema. Minimum requirements of an MRL protocol should consist of a gadolinium-based contrast-enhanced T1-weighted gradient-recalled echo sequence combined with T2-weighted magnetic resonance imaging, with acquisition at least 30 minutes after injection of contrast material.

MR Lymphangiography

림프부종의 수술적 치료는 최근 늘어나고 있으며 그에 따른 림프관 평가를 위해 자기공명영상 획득이 증가하고 있다. 전통적인 T2 강조영상에서부터 삼차원 영상에 이르기까지 많은 발전이 이루어지고 있는 분야이다. 삼차원 영상으로는 spoiled gradient echo 영상이 있고 그 변형기법들이 시행되고 있으며 영상에 필수적인 지방억제기법은 최근 mDixon 기법이 각광받고 있다.

Diagnosis and Staging of Lymphedema

Lymphedema often is confused with other causes of extremity edema and enlargement. Understanding the risk factors and physical examination signs of lymphedema can enable the health care practitioner to accurately diagnose patients ∼90% of the time. Confirmatory diagnosis of the disease is made using lymphoscintigraphy. It is important to correctly diagnose patients with lymphedema so that they can be managed appropriately.

Diagnostic Accuracy of Lymphoscintigraphy for Lymphedema and Analysis of False-Negative Tests

Lymphedema is the chronic enlargement of tissue due to inadequate lymphatic function. Diagnosis is made by history and physical examination and confirmed with lymphoscintigraphy. The purpose of this study was to assess the accuracy of lymphoscintigraphy for the diagnosis of lymphedema and to determine characteristics of patients with false-negative tests.

[Complex decongestive therapy]

The amount of physical pressure plays an important role in complex decongestive therapy (CDT). As a function of pressure, microcirculation takes place between blood vessels and tissue. As part of the total lymphatic system, lymphatic vessels transport the lymphatic load from the interstitial space to the blood stream. The lymphatic vessel system, characterized by specific anatomical conditions like initial lymphatic vessels, precollectors, collectors, and lymphatic strains, is the therapeutic target of complex decongestive therapy. Components of CDT include manual lymphatic drainage, compression therapy, decongestive kinesitherapy, and good skin care, which increase the transport capacity of the lymphatic vessel system. Currently, CDT is acknowledged as the main conservative treatment of lymphedema of primary and secondary genesis, lipolymphedema, and phlebolymphedema. In clinical practice, we are increasingly confronted with edema of multifactorial genesis requiring a critical discussion and stocktaking of comprehensive clinical findings in terms of the indication for CDT. Therapeutic success depends on a joint application of all CDT components and patient compliance. To an increasing extent, medical research tries to combine successfully CDT with adjunct treatment options.

The Lymphatic System in Disease Processes and Cancer Progression

Advances in our understanding of the structure and function of the lymphatic system have made it possible to identify its role in a variety of disease processes. Because it is involved not only in fluid homeostasis but also in immune cell trafficking, the lymphatic system can mediate and ultimately alter immune responses. Our rapidly increasing knowledge of the molecular control of the lymphatic system will inevitably lead to new and effective therapies for patients with lymphatic dysfunction. In this review, we discuss the molecular and physiological control of lymphatic vessel function and explore how the lymphatic system contributes to many disease processes, including cancer and lymphedema.