Reliability, concurrent validity and clinical feasibility of measurement methods determining local tissue water in patients with lower limb lymphedema and healthy controls.

PURPOSE: To investigate reliability, concurrent validity and clinical feasibility of local tissue water measurements in patients with lower limb lymphedema and healthy controls. METHODS: In this cross-sectional study the Moisture Meter D Compact device® (MMDC) measurement and "pitting test" were performed three times by two assessors to test intra- and inter-rater reliability in 47 patients and 30 healthy controls. To investigate the between-session reliability, 29 patients and 21 healthy controls were reassessed two weeks later. Time efficiency and practical limitations were evaluated. The concurrent validity was investigated between the two tests. Clinical trial registration number: NCT:05269264. RESULTS: Of the MMDC values, 58% showed strong to very strong intra-rater reliability, 32% showed strong to very strong inter-rater reliability and 36% had strong to very strong between-session reliability. Absolute values had generally a higher reliability than inter-limb or leg-to-arm ratio values. The pitting test had nil to perfect agreement between assessments (Cohen's kappa = -0.03-1.00) with fewer practical limitations and shorter performance time than the MMDC. Between both tests nil to a moderate relationship was found (Kendall's tau c = 0.00-0.60). CONCLUSION: The MMDC and pitting test are reliable and feasible measurements to assess local tissue water depending on the location, but should not be used interchangeably.

Patients with lower limb lymphedema are preferably assessed by the same assessor.The Moisture Meter D Compact device measurements and pitting test are reliable measurements methods depending on the location of the reference point.The Moisture Meter D Compact device measurement and pitting test have few practical limitations and can be performed in a limited time.The Moisture Meter D Compact device measurements and the pitting test should not be used interchangeably, but rather complementary.

Reliability, concurrent validity, and clinical feasibility of measurement methods determining volume in patients with lower limb lymphedema and healthy controls.

PURPOSE: To investigate reliability, concurrent validity, and clinical feasibility of measurements assessing volume in patients with lower limb lymphedema (LLL) and healthy controls. MATERIALS AND METHODS: To investigate intra- and interrater reliability, 47 patients with LLL and 30 healthy controls were assessed three times by two assessors. To investigate between session reliability, 50 participants were reassessed two weeks later. Each assessment included measurements of the midline region (hip circumference; suprapubic volume), leg volume (perimeter every 4 cm; Perometer®), and foot volume (water displacement; figure-of-eight method). Concurrent validity was assessed with correlation coefficients. Measurements were timed and practical limitations were reviewed. Clinical trial registration number: NCT: 05269264. RESULTS: Measurements of the total volume of different regions showed weak to very high intraclass correlation coefficients (ICCs) (0.131-998). Absolute and relative volume differences had lower ICC values (0.360-0.976). A strong correlation was found between the total volumes of the same region. The Perometer® and figure-of-eight method were the fastest method for leg and foot volume, respectively. CONCLUSIONS: The assessed total volumes might be more valuable in assessing the evolution of volume in bilateral LLL than the calculated absolute and relative differences between both limbs. The Perometer® and figure-of-eight method were the most time efficient for leg and foot volume, respectively.Implications for rehabilitationLymphedema is a chronic condition for which a reliable and clinically feasible assessment of volume is essential for the diagnosis, treatment decisions, and the evaluation of the treatment.This study shows that the total leg/foot volumes were more reliable than the calculated absolute and relative differences between both limbs and could therefore more valuable to evaluate bilateral lower limb lymphedema.For the assessment of leg volume, the Perometer® was the most reliable and fastest method.For the evaluation of the foot volume, the figure-of-eight method was overall the best method.

Profound and selective lymphopaenia in primary lymphatic anomaly patients demonstrates the significance of lymphatic-lymphocyte interactions.

Introduction: The lymphatic system has a pivotal role in immune homeostasis. To better understand this, we investigated the impact of Primary Lymphatic Anomalies (PLA) on lymphocyte numbers and phenotype. Methods: The study comprised (i) a retrospective cohort: 177 PLA subjects from the National Primary Lymphatic Anomaly Register with clinical and laboratory data, and (ii) a prospective cohort: 28 patients with PLA and 20 healthy controls. Patients were subdivided using established phenotypic diagnostic categories and grouped into simplex (localised tissue involvement only) and systemic (involvement of central lymphatics). Further grouping variables included genital involvement and the likelihood of co-existent intestinal lymphangiectasia. Haematology laboratory parameters were analysed in both cohorts. In the prospective cohort, prospective blood samples were analysed by flow cytometry for markers of proliferation, differentiation, activation, skin-homing, and for regulatory (CD4+Foxp3+) T cells (Treg). Results: In patients with PLA, lymphopaenia was frequent (22% of subjects), affected primarily the CD4+ T cell subset, and was more severe in subjects with systemic versus simplex patterns of disease (36% vs 9% for lymphopaenia; 70% vs 33% for CD4+ cells). B cells, NK cells and monocytes were better conserved (except in GATA2 deficiency characterised by monocytopaenia). Genital oedema and likelihood of concomitant intestinal lymphangiectasia independently predicted CD4+ T cell depletion. Analysing CD4+ and CD8+ T cells by differentiation markers revealed disproportionate depletion of naïve cells, with a skewing towards a more differentiated effector profile. Systemic PLA conditions were associated with: increased expression of Ki67, indicative of recent cell division, in naïve CD4+, but not CD8+ T cells; increased levels of activation in CD4+, but not CD8+ T cells; and an increased proportion of Treg. Skin-homing marker (CCR10, CLA and CCR4) expression was reduced in some patients with simplex phenotypes. Discussion: Patients with PLA who have dysfunctional lymphatics have a selective reduction in circulating lymphocytes which preferentially depletes naïve CD4+ T cells. The presence of systemic disease, genital oedema, and intestinal lymphangiectasia independently predict CD4 lymphopaenia. The association of this depletion with immune activation and increased circulating Tregs suggests lymphatic-lymphocyte interactions and local inflammatory changes are pivotal in driving immunopathology.

Erythematous capillary-lymphatic malformations mimicking blood vascular anomalies.

Superficial erythematous cutaneous vascular malformations are assumed to be blood vascular in origin, but cutaneous lymphatic malformations can contain blood and appear red. Management may be different and so an accurate diagnosis is important. Cutaneous malformations were investigated through 2D histology and 3D whole-mount histology. Two lesions were clinically considered as port-wine birthmarks and another 3 lesions as erythematous telangiectasias. The aims were (i) to demonstrate that cutaneous erythematous malformations including telangiectasia can represent a lymphatic phenotype, (ii) to determine if lesions represent expanded but otherwise normal or malformed lymphatics, and (iii) to determine if the presence of erythrocytes explained the red color. Microscopy revealed all lesions as lymphatic structures. Port-wine birthmarks proved to be cystic lesions, with nonuniform lymphatic marker expression and a disconnected lymphatic network suggesting a lymphatic malformation. Erythematous telangiectasias represented expanded but nonmalformed lymphatics. Blood within lymphatics appeared to explain the color. Blood-lymphatic shunts could be detected in the erythematous telangiectasia. In conclusion, erythematous cutaneous capillary lesions may be lymphatic in origin but clinically indistinguishable from blood vascular malformations. Biopsy is advised for correct phenotyping and management. Erythrocytes are the likely explanation for color accessing lymphatics through lympho-venous shunts.

Redefining WILD syndrome: a primary lymphatic dysplasia with congenital multisegmental lymphoedema, cutaneous lymphovascular malformation, CD4 lymphopaenia and warts.

BACKGROUND: Primary lymphoedema (PL) syndromes are increasingly recognised as presentations of complex genetic disease, with at least 20 identified causative genes. Recognition of clinical patterns is key to diagnosis, research and therapeutics. The defining criteria for one such clinical syndrome, 'WILD syndrome' (Warts, Immunodeficiency, Lymphoedema and anogenital Dysplasia), have previously depended on a single case report. METHODS AND RESULTS: We present 21 patients (including the first described case) with similar clinical and immunological phenotypes. All had PL affecting multiple segments, with systemic involvement (intestinal lymphangiectasia/pleural or pericardial effusions) in 70% (n=14/20). Most (n=20, 95%) had a distinctive cutaneous lymphovascular malformation on the upper anterior chest wall. Some (n=10, 48%) also had hyperpigmented lesions resembling epidermal naevi (but probably lymphatic in origin). Warts were common (n=17, 81%) and often refractory. In contrast to the previous case report, anogenital dysplasia was uncommon-only found in two further cases (total n=3, 14%). Low CD4 counts and CD4:CD8 ratios typified the syndrome (17 of 19, 89%), but monocyte counts were universally normal, unlike GATA2 deficiency. CONCLUSION: WILD syndrome is a previously unrecognised, underdiagnosed generalised PL syndrome. Based on this case series, we redefine WILD as 'Warts, Immunodeficiency, andLymphatic Dysplasia' and suggest specific diagnostic criteria. The essential criterion is congenital multisegmental PL in a 'mosaic' distribution. The major diagnostic features are recurrent warts, cutaneous lymphovascular malformations, systemic involvement (lymphatic dysplasia), genital swelling and CD4 lymphopaenia with normal monocyte counts. The absence of family history suggests a sporadic condition, and the random distribution of swelling implicates mosaic postzygotic mutation as the cause.

Image registration and subtraction in dynamic magnetic resonance lymphangiography (MRL) of the legs.

Dynamic contrast-enhanced magnetic resonance lymphangiography (DCE-MRL) is regularly reported as unable to depict lymphatic vessels in healthy limbs. In this study, we aim to improve lymph vessel conspicuity with appropriate registration and subtraction of a reference baseline image. Five unaffected individuals and a single unilateral primary lymphoedema patient were recruited to undergo fat suppressed 3D T 1 weighted spoiled gradient echo imaging of the lower limbs at 3.0 T. Images were quality assessed by two physicians and a medical physicist following registration via one of six registration pipelines, and subtraction of the first post-contrast dynamic image (PC1). Wilcoxon non-parametric testing was performed to compare image quality ranking vs the unregistered images and inter-rater reliability estimated using intraclass correlation coefficient. Signal enhancement curves were also computed in lymphatic vessels for two participants. Subtraction images were considered to improve lymphatic visibility, and three registration pipelines significantly (p < 0.05) outranked those without registration. Those registered to PC1 with an affine and elastic approach were rated best quality (p = 0.006). Moderate inter-rater reliability was observed (intraclass correlation coefficient = 0.71) and signal enhancement behaviour appears affected by registration when motion is evident across the DCE-MRL series. We therefore conclude that lymphatic vessel visibility in DCE-MRL images can be improved with registration and baseline subtraction.

Investigation of clinical characteristics and genome associations in the 'UK Lipoedema' cohort.

Lipoedema is a chronic adipose tissue disorder mainly affecting women, causing excess subcutaneous fat deposition on the lower limbs with pain and tenderness. There is often a family history of lipoedema, suggesting a genetic origin, but the contribution of genetics is currently unclear. A tightly phenotyped cohort of 200 lipoedema patients was recruited from two UK specialist clinics. Objective clinical characteristics and measures of quality of life data were obtained. In an attempt to understand the genetic architecture of the disease better, genome-wide single nucleotide polymorphism (SNP) genotype data were obtained, and a genome wide association study (GWAS) was performed on 130 of the recruits. The analysis revealed genetic loci suggestively associated with the lipoedema phenotype, with further support provided by an independent cohort taken from the 100,000 Genomes Project. The top SNP rs1409440 (ORmeta ≈ 2.01, Pmeta ≈ 4 x 10-6) is located upstream of LHFPL6, which is thought to be involved with lipoma formation. Exactly how this relates to lipoedema is not yet understood. This first GWAS of a UK lipoedema cohort has identified genetic regions of suggestive association with the disease. Further replication of these findings in different populations is warranted.

Case Report: Progressive central conducting lymphatic abnormalities in the RASopathies. Two case reports, including successful treatment by MEK inhibition.

The RASopathies are a group of genetic conditions resulting from mutations within the RAS/mitogen-activated protein kinase (RAS-MAPK) pathway. Lymphatic abnormalities are commonly associated with these conditions, however central conducting lymphatic abnormalities (CCLA) have only recently been described. CCLAs may be progressive and can result in devastating systemic sequelae, such as recurrent chylothoraces, chylopericardium and chylous ascites which can cause significant morbidity and even mortality. Improvements in imaging modalities of the central lymphatics have enhanced our understanding of these complex abnormalities. Management is challenging and have mainly consisted of diuretics and invasive mechanical drainages. We describe two adult males with Noonan syndrome with a severe and progressive CCLA. In one patient we report the therapeutic role of targeted molecular therapy with the MEK inhibitor 'Trametinib', which has resulted in dramatic, and sustained, clinical improvement. The successful use of MEK inhibition highlights the importance of understanding the molecular cause of lymphatic abnormalities and utilising targeted therapies to improve quality of life and potentially life expectancy.

Paediatric lymphoedema: An audit of patients seen by the paediatric and primary lymphoedema group of vascular European Reference Network (VASCERN).

Little is known about the overall prevalence of lymphoedema in children and the types of paediatric lymphoedema seen by specialist centres. Therefore, this study was aimed to provide a profile of children with primary or secondary lymphoedema seen by the expert centres of the paediatric and primary lymphoedema working group (PPL-WG) of VASCERN and to compare the profile between the different countries. A retrospective review of all children (aged up to 18 years) seen for the first time by the expert centres over one year (2019) was carried out. Lymphoedema-, patient- and genetics-related data was collected and described for the whole group and compared between the different European countries/UK. In 2019, a total of 181 new children were seen by eight expert centres. For primary lymphoedema, the phenotype was based on the St George's classification of lymphatic anomalies. The percentages diagnosed according to each category were: 7.2% for syndromic lymphoedema, 2.8% for systemic/visceral involvement, 30.4% for congenital, 35.9% for late-onset lymphoedema and 19.3% for vascular/lymphatic malformations. 4.4% had secondary lymphoedema. Nearly 10% of all children had had at least one episode of cellulitis. The median delay from onset of symptoms to being seen by an expert centre was 2.4 years. In 44.4% of the children with primary lymphoedema a genetic test was performed, of which 35.8% resulted in a molecular diagnosis. Across the different centres, there was a wide variety in distribution of the different categories of paediatric lymphoedema diagnosed and the frequency of genetic testing. In conclusion, this paper has demonstrated that there is a large delay between the onset of paediatric lymphoedema and the first visit in the expert centres and that an episode of cellulitis is a relatively common complication. Diagnostic variation across the centres may reflect different referral criteria. Access to genetic testing was limited in some centres. It is recommended that these issues are addressed in the future work of the PPL-WG to improve the referral to the expert centres and the consistency in service provision for paediatric lymphoedema in Europe.

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.

The St George's Classification Algorithm of Primary Lymphatic Anomalies.

Clinicians and scientists at St George's University Hospital have collaborated to develop a classification algorithm for primary lymphatic anomalies. Instruction is offered on how to apply the algorithm in clinical practice to refine the diagnosis of primary lymphedema and guide on genetic testing and management. It can also be used to interpret mutation testing results of uncertain significance. The algorithm has evolved as more genes have been discovered, and it remains a "work in progress" as further discoveries are made. This transformational approach has revolutionized the understanding and classification of primary lymphatic anomalies.

Update and audit of the St George's classification algorithm of primary lymphatic anomalies: a clinical and molecular approach to diagnosis.

Primary lymphatic anomalies may present in a myriad of ways and are highly heterogenous. Careful consideration of the presentation can lead to an accurate clinical and/or molecular diagnosis which will assist with management. The most common presentation is lymphoedema, swelling resulting from failure of the peripheral lymphatic system. However, there may be internal lymphatic dysfunction, for example, chylous reflux, or lymphatic malformations, including the thorax or abdomen. A number of causal germline or postzygotic gene mutations have been discovered. Some through careful phenotyping and categorisation of the patients based on the St George's classification pathway/algorithm. The St George's classification algorithm is aimed at providing an accurate diagnosis for patients with lymphoedema based on age of onset, areas affected by swelling and associated clinical features. This has enabled the identification of new causative genes. This update brings the classification of primary lymphatic disorders in line with the International Society for the Study of Vascular Anomalies 2018 classification for vascular anomalies. The St George's algorithm considers combined vascular malformations and primary lymphatic anomalies. It divides the types of primary lymphatic anomalies into lymphatic malformations and primary lymphoedema. It further divides the primary lymphoedema into syndromic, generalised lymphatic dysplasia with internal/systemic involvement, congenital-onset lymphoedema and late-onset lymphoedema. An audit and update of the algorithm has revealed where new genes have been discovered and that a molecular diagnosis was possible in 26% of all patients overall and 41% of those tested.

Lymphoscintigraphic Abnormalities Associated with Milroy Disease and Lymphedema-Distichiasis Syndrome.

Background: Primary lymphedema is genetically heterogeneous. Two of the most common forms of primary lymphedema are Milroy disease (MD) and lymphedema-distichiasis syndrome (LDS). This study aims to look further into the pathogenesis of the two conditions by analyzing the lymphoscintigram images from affected individuals to ascertain if it is a useful diagnostic tool. Methods and Results: The lymphoscintigrams of patients with MD and LDS were analyzed, comparing the images and transport parameters of the two genotypes against a control population. Lymphoscintigrams were available for 12 MD and 16 LDS patients (all genetically proven diagnoses). Eight of the 12 (67%) lymph scans performed on patients with MD demonstrated little or no uptake from the initial lymphatics and poor visualization of the inguinal lymph nodes. These changes were consistent with a "functional aplasia," that is, the lymphatic vessels were present but appeared to be ineffective in absorbing the interstitial fluid into the lymphatic system. In patients with LDS the lymphoscintigraphic appearances were different. In 12 of the 16 scans (75%), the lymph scans were highly suggestive of lymphatic collector reflux. Quantification revealed a significantly reduced uptake of tracer within the inguinal lymph nodes and a higher residual activity in the feet at 2 hours in MD compared with LDS and compared with controls. Conclusion: Lymphoscintigraphic imaging and quantification can be characteristic in specific genetic forms of primary lymphedema and may be useful as an additional tool for in-depth phenotyping, leading to a more accurate diagnosis and providing insight into the underlying mechanism of disease.

LIMPRINT in Australia.

Background and Study Objective: Australia was one of nine participating countries in the epidemiology Phase II Lymphoedema Impact and Prevalence - International (LIMPRINT) project to determine the number of people with chronic edema (CO) in local health services. Methods and Results: Data collection occurred through questionnaire-based interviews and clinical assessment with provided LIMPRINT tools. Four different types of services across three states in Australia participated. A total of 222 adults participated with an age range from 22 to 102 years, and 60% were female. Site 1 included three residential care facilities (54% of participants had swelling), site 2 was community-delivered aged care services (24% of participants had swelling), site 3 was a hospital setting (facility-based prevalence study; 28% of participants had swelling), and site 4 was a wound treatment center (specific patient population; 100% of participants had swelling). Of those with CO or secondary lymphedema, 93% were not related to cancer, the lower limbs were affected in 51% of cases, and 18% of participants with swelling reported one or more episodes of cellulitis in the previous year. Wounds were identified in 47% (n = 105) of all participants with more than half of those with wounds coming from the dedicated wound clinic. Leg/foot ulcer was the most common type of wound (65%, n = 68). Conclusions: Distances between services, lack of specialized services, and various state funding models contribute to inequities in CO treatment. Understanding the high number of noncancer-related CO presentations will assist health services to provide timely effective care and improve referral pathways.

A high-resolution tape sensor improves the accuracy of applied pressure profiles during lower-leg bandaging - results from a study using a fibre-optic sensing tape.

Compression bandaging is a mainstay practice in the treatment of conditions such as chronic wounds and lymphoedema. However, the ability of practitioners to measure bandage application to a desired pressure profile is difficult because of sensor limitations. We have used a novel fibre-optic-based, high-resolution sub-bandage pressure monitor to measure adherence to a target pressure gradient during compression bandaging. Participants of various experience (n = 46) were asked to bandage a lower-leg manikin to a gradient of 40 (ankle) to 20 mmHg (proximal calf) in both a blinded trial and subsequently with sensor feedback. Mean pressures across all sensors for both the blind and sensor-guided trials approximated a target mean of 30 mmHg. However, the mean gradient achieved in the blinded trial showed an inverse pressure gradient to the target with a high-pressure region at the mid-calf (44 ± 19 mmHg). Correlation to the target gradient improved from R2 = 0·62 during the blind trial to 0·93 using sensor feedback, with a gradient that closely approximated the target. This demonstrates the use of high-resolution sub-bandage pressure sensing in improving the ability of practitioners to achieve a target pressure gradient in compression bandaging for clinical use and training.

The Lymphatic Response to Injury with Soft-Tissue Reconstruction in High-Energy Open Tibial Fractures of the Lower Extremity.

BACKGROUND: Severe compound tibial fractures are associated with extensive soft-tissue damage, resulting in disruption of lymphatic pathways that leave the patient at risk of developing chronic lymphedema. There are limited data on lymphatic response following lower limb trauma. Indocyanine green fluorescence lymphography is a novel, real-time imaging technique for superficial lymphatic mapping. The authors used this technique to image the superficial lymphatic vessels of the lower limbs in patients with severe compound tibial fracture. METHODS: Baseline demographics and clinical and operative details were recorded in a prospective cohort of 17 patients who had undergone bone and soft-tissue reconstruction after severe compound tibial fracture between 2009 and 2014. Normal lymphatic images were obtained from the patients' noninjured limbs as a control. In this way, the authors investigated any changes to the normal anatomy of the lymphatic system in the affected limbs. RESULTS: Of the 17 patients, eight had free muscle flaps with split-thickness skin grafting, one had a free fasciocutaneous flap, one had a full-thickness skin graft, six had local fasciocutaneous flaps, and one had a pedicled gastrocnemius flap. None of the free flaps demonstrated any functional lymphatic vessels; the fasciocutaneous flaps and the skin graft demonstrated impaired lymphatic vessel function and dermal backflow pattern similar to that in lymphedema. Local flaps demonstrated lymphatic blockage at the scar edge. CONCLUSION: Severe compound fractures and the associated soft-tissue injury can result in significant lymphatic disruption and an increased risk for the development of chronic lymphedema.

Inter-Changeability of Impedance Devices for Lymphedema Assessment.

Impedance technology is a popular technique for the early detection of lymphedema. The preferred approach is to use bioimpedance spectroscopy (BIS), with measurements being made with the subject lying supine, although attempts have been made to use single or multiple frequency impedance measurements obtained while the subject is standing. The aim of the present study was to determine the equivalence of these different approaches. Impedance measurements of the individual limbs of 37 healthy individuals were determined using both a stand-on, multi-frequency impedance device and a supine impedance spectroscopy instrument. Significant differences were found between the instruments in both absolute impedance values and, importantly, inter-limb impedance ratios. Since impedance ratios in healthy individuals provide the reference standard for detection of lymphedema, these data indicate that the methods are not interchangeable. Consideration of the errors associated with each method indicates that the BIS remains the preferred method for lymphedema detection.

Development and validation of a custom made indocyanine green fluorescence lymphatic vessel imager.

Lymphoedema is a chronic progressive condition often producing significant morbidity. An in-depth understanding of an individual's lymphatic architecture is valuable both in the understanding of underlying pathology and for targeting and tailoring treatment. Severe lower limb injuries resulting in extensive loss of soft tissue require transposition of a flap consisting of muscle and/or soft tissue to close the defect. These patients are at risk of lymphoedema and little is known about lymphatic regeneration within the flap. Indocyanine green (ICG), a water-soluble dye, has proven useful for the imaging of lymphatic vessels. When injected into superficial tissues it binds to plasma proteins in lymph. By exposing the dye to specific wavelengths of light, ICG fluoresces with near-infrared light. Skin is relatively transparent to ICG fluorescence, enabling the visualization and characterization of superficial lymphatic vessels. An ICG fluorescence lymphatic vessel imager was manufactured to excite ICG and visualize real-time fluorescence as it travels through the lymphatic vessels. Animal studies showed successful ICG excitation and detection using this imager. Clinically, the imager has assisted researchers to visualize otherwise hidden superficial lymphatic pathways in patients postflap surgery. Preliminary results suggest superficial lymphatic vessels do not redevelop in muscle flaps.