Lymphatic Anatomy Research Articles

ABNORMAL LYMPHATIC PHENOTYPE IN A CRISPR MOUSE MODEL OF THE HUMAN LYMPHEDEMA-CAUSING CONNEXIN47 R260C POINT MUTATION

Connexin proteins form gap junctions controlling exchange of ions and small molecules between cells and play an important role in movement of lymph within lymphatic vessels. Connexin47 (CX47) is highly expressed in lymphatic endothelial cells and CX47 missense mutations, i.e., R260C, cosegregate with primary lymphedema in humans. However, studies utilizing CX47 knockout mice have failed to demonstrate any lymphatic anomalies. To unravel the lymphatic consequences of expressing a mutant CX47 protein, we used CRISPR technology to create a mouse carrying a Cx47 missense mutation (Cx47R259C) equivalent to the human CX47R260C missense mutation associated with human primary lymphedema. Intradermal Evans Blue dye injection identified a 2-fold increase in regional lymph nodes in homozygous Cx47R259C mice compared to wildtype, particularly in the jugular region (4.8 ± 0.4 and 2.0 ± 0.0, respectively, p<0.01). Associated lymphatic channels were increased in Cx47R259C mice and mesenteric lymph reflux occurred in homozygous Cx47R259C mice but not in wildtype. Contractility of superficial cervical lymphatics, assessed by pressure myography, was reduced in homozygous Cx47R259C mice compared to wildtype. In conclusion, our data are the first to demonstrate a role for the Cx47 protein in lymphatic anatomy and function. This phenotype is similar to that found with other valve deficient mouse mutants, e.g., in Foxc2. Of significance, this study is the first to use CRISPR technology to develop a pre-clinical model of primary lymphedema and demonstrates the importance of distinguishing between lack of and presence of mutant protein when developing clinically relevant animal models for translation of pre-clinical findings.

Back and forth: History of and new insights on the vertebrate lymphatic valve.

Lymphatic valves develop from pre‐existing endothelial cells through a step‐wise process involving complex changes in cell shape and orientation, along with extracellular matrix interactions, to form two intraluminal leaflets. Once formed, valves prevent back‐flow within the lymphatic system to ensure drainage of interstitial fluid back into the circulatory system, thereby serving a critical role in maintaining fluid homeostasis. Despite the extensive anatomical characterization of lymphatic systems across numerous genus and species dating back several hundred years, valves were largely thought to be phylogenetically restricted to mammals. Accordingly, most insights into molecular and genetic mechanisms involved in lymphatic valve development have derived from mouse knockouts, as well as rare diseases in humans. However, we have recently used a combination of imaging and genetic analysis in the zebrafish to demonstrate that valves are a conserved feature of the teleost lymphatic system. Here, we provide a historical overview of comparative lymphatic valve anatomy together with recent efforts to define molecular pathways that contribute to lymphatic valve morphogenesis. Finally, we integrate our findings in zebrafish with previous work and highlight the benefits that this model provides for investigating lymphatic valve development.

Intranodal CT Lymphangiography with Water-soluble Iodinated Contrast Medium for Imaging of the Central Lymphatic System.

Background Dynamic contrast-enhanced MR lymphangiography (DCMRL) is the reference standard used to diagnose various thoracic lymphatic disorders, such as traumatic chylothorax and plastic bronchitis. However, accessibility and logistical challenges have prevented the wide dissemination of this technology. Purpose To evaluate the feasibility of intranodal CT lymphangiography (ICTL) in the diagnosis and planning of subsequent intervention in patients with thoracic lymphatic disorders. Materials and Methods In this retrospective review, five women suspected of having lymphatic abnormalities (ranging from traumatic chylothorax to plastic bronchitis) and with contraindications to MRI underwent ICTL from September 2019 to May 2020. Needles (25 gauge) were placed in the bilateral inguinal lymph nodes with US guidance, and water-soluble iodinated contrast material was injected. CT fluoroscopy was used to monitor the opacification of the cisterna chyli to determine the timing of CT. After ICTL, the thoracic duct was catheterized, and lymphangiography was performed through the thoracic duct catheter. The ICTL and subsequent lymphangiographic findings were then visually compared by using three-dimensional reconstructions. Results Intranodal injection of water-soluble contrast medium was successful in all patients evaluated (five women; mean age, 68 years ± 11 [standard deviation]; range, 53-83 years). The central lymphatics were opacified in four of the five women, demonstrating abnormal pulmonary lymphatic flow from the thoracic duct into the lung parenchyma. In one of the five women, thoracic duct injection showed successful ligation of the thoracic duct. The time elapsed from injection of contrast medium to visualization of the thoracic duct ranged from 2 to 27 minutes. ICTL and lymphangiographic findings matched well. Conclusion Intranodal CT lymphangiography sufficiently depicted central lymphatic anatomy in patients with lymphatic abnormalities, thereby demonstrating its use as a feasible alternative to more technically challenging methods, such as dynamic contrast-enhanced MR lymphangiography. © RSNA, 2021.

Lower limb lymphedema staging based on magnetic resonance lymphangiography

ObjectiveDermal backflow (DBF) and reduced lymphatic visualization are common findings of lymphedema on various imaging modalities. However, there is a lack of knowledge about how these findings vary with the anatomic location and severity of lymphedema, and previous reports using indocyanine green lymphography or lymphoscintigraphy show variable results. Magnetic resonance lymphangiography (MRL) is expected to clarify this clinical question due to its superior ability for lymphatic visualization. This retrospective study aimed to investigate the following: (1) Are there any characteristic patterns for DBF and lymphatics' visualization, depending on the anatomic location within lower limbs and severity of lymphedema? (2) Is it possible to classify the severity of lymphedema based on MRL findings? MethodsTwo radiologists performed consensus readings of MRL of 56 patients (112 limbs) with lower-limb lymphedema. The frequency of visualized DBF and lymphatics was analyzed in six regions in each lower limb. The results were compared with the International Society of Lymphology clinical stages and etiology of lymphedema. Characteristic findings were categorized and compared with the clinical stage and duration of lymphedema. ResultsDBF and lymphatics were observed more frequently in the distal regions than the proximal regions of lower limbs. DBF appeared more frequently as the clinical stage increased, reaching statistical significance (P < 10−3) between stages 0 or I and II. DBF above the knee joint was rarely observed (0.48%) in early stages (0 and I) but appeared more frequently (13.5%, P < 10−5) in stage II. Lymphatics appeared less frequently as the stage progressed, with significant differences (P < .05) between stages I and II and between II and III. The frequency of lymphatics above the knee joint decreased significantly (P < .05) between stages I and II and between II and III as the stage progressed, reaching 0% in stage III. An MRL staging was proposed and showed significant positive correlations with the clinical stage (r = 0.79, P < .01) and the duration of lymphedema (r = 0.57, P < .01). ConclusionsMRL-specific patterns of DBF and lymphatics that depended on the site within the lower limb and clinical stage were shown. The DBF pattern differed from those observed in previous studies with other imaging techniques. The proposed MRL staging based on these characteristic findings allows new stratification of patients with lymphedema. Combined with its excellent ability to visualize lymphatic anatomy, MRL could enable a more detailed understanding of individual patient's pathology, useful for determining the most appropriate treatment.

Eyelid Lymphatics: An Anatomical Study by Microdissection.

To obtain further understanding of the eyelid lymphatic anatomy. Thirty-two halves of eyelids from 16 fresh fetus cadavers were studied by microdissection using a mixture of 3% Prussian blue and chloroform to visualize the lymphatic vessels. Three layers of lymphatic plexuses were demonstrated in the eyelids: a superficial or preorbicularis muscle plexus; a pretarsal or postorbicular muscle plexus; and a deep or posttarsal plexus. Furthermore, communicating branches among these plexuses were also spotted. The study results demonstrated the topographic distribution of the eyelid lymphatic vessels and confirmed the existence of communicating branches. This discovery will be conducive to understanding the route and mechanism by which inflammation of the eyelid spreads and cancer disseminates. It also provides anatomical insights to apply during eyelid surgery with regard to the prevention of possible eyelid lymphatic injury.

Liver lymphatic anatomy and role in systemic lymphatic disease

ObjectivesTo characterize hepatic to systemic lymphatic connections in patients with systemic lymphatic disease using intra-hepatic lymphangiography and to compare outcomes after lymphatic intervention.MethodsIn this retrospective study, patients with intra-hepatic lymphangiography from May 2014 – April 2019 at our institution were included. Imaging review was performed and hepatic lymphatic connections and flow patterns were characterized. Clinical data were reviewed and comparisons between patients undergoing lymphatic intervention with or without abnormal hepatic lymphatics were performed.ResultsDuring the study period, 105 patients underwent intra-hepatic lymphangiography. Primary clinical presentation included ascites (19/105), chylothorax (27/105), plastic bronchitis (PB) (17/105), and protein losing enteropathy (PLE) (42/105). Five categories of hepatic lymphatic connections and flow patterns were identified (%): normal (25%, 26/105), hepatoperitoneal (12%, 13/105), hepatopulmonary (10.5%, 11/105), hepatomesenteric (7.5%, 8/105), and hepatoduodenal (41%, 43/105) with four patients having more than one abnormal pattern. A comparison between clinical presentation and imaging category revealed an increased likelihood of having ascites with hepatoperitoneal (p < .0001), chylothorax/PB with hepatopulmonary (p = .01), and PLE with hepatoduodenal (p < .001) connections. Seventy-six patients had a lymphatic intervention, 24% with normal, and 76% with abnormal liver lymphatics. There was no difference in length of hospital stay or mortality between the two groups, but there was a prolonged time to symptom resolution (p = .006) and persistent symptoms after 6 months (5% vs 44%, p = .002) in the group with abnormal liver lymphatics.ConclusionWe identified five liver lymphatic imaging categories with a substantial correlation to presenting lymphatic disease. Abnormal imaging patterns correlated with increased morbidity. Evaluation of liver lymphatics should be considered in patients with a systemic lymphatic disease if central lymphatic imaging is normal.Key Points• We identified five liver lymphatic imaging patterns: normal, hepatoperitoneal, hepatomesenteric, hepatopulmonary, and hepatoduodenal.• Imaging patterns were correlated with disease presentation (normal – chylothorax/PB, hepatoperitoneal – ascites/chylothorax, hepatopulmonary – chylothorax/PB, hepatoduodenal – PLE).• Abnormal imaging patterns correlated with increased morbidity.

Role of the Cadaver Lab in Lymphatic Microsurgery Education: Validation of a New Training Model

Background Microsurgical transplantation of vascularized lymph nodes (VLNT) or lymphatic vessels (VLVT) alongside derivative lymphaticovenous procedures are promising approaches for treatment of lymphedema. However, clinically relevant training models for mastering these techniques are still lacking. Here we describe a new training model in human cadaver and validate its use as training tool for microsurgical lymphatic reconstruction. Methods 10 surgeons with previous exposure to microsurgery were trained in a controlled environment. Lymphatic vessel mapping and dissection in 4 relevant body regions, harvesting of five different VLNTs and one VLVT were performed in 5 fresh-frozen cadavers. The number of lymphatic vessels and lymph nodes for each VLNT were recorded. Finally, the efficacy of this model as training tool was validated using the Dundee Ready Education Environment Measure (DREEM). Results The average cumulative DREEM score over each category was 30,75 (max = 40) while individual scoring for each relevant category revealed highly positive ratings from the perspective of teaching (39,3), training 40,5 (max = 48) and self perception of the training 30,5 (max = 32) from all participants. The groin revealed the highest number of lymphatic vessels (3.2 ± 0.29) as all other regions on the upper extremity, while the gastroepiploic VLNT had the highest number of lymph nodes (4.2 ± 0.37). Conclusions This human cadaver model represents a new, reproducible “all-in-one” tool for effective training in lymphatic microsurgery. Its unique diligence in accurately reproducing human lymphatic anatomy, should make this model worth considering for each microsurgeon willing to approach lymphatic reconstruction.

Lymphatic Senescence: Current Updates and Perspectives.

Simple SummaryThe lymphatic system is involved in tissue homeostasis, immune processes as well as transport of lipids, proteins and pathogens. Aging affects all physiological systems. However, it is not well studied how aging affects the lymphatic vasculature. Therefore, this review aims at investigating how senescence could lead to changes in the structure and function of the lymphatic vessels. We report that lymphatic senescence is associated with alterations in lymphatic muscles and nerve fibers, lymphatic endothelial cells membrane dysfunction, as well as changes in lymphatic pump, acute inflammation responses and immune function.Lymphatic flow is necessary for maintenance of vital physiological functions in humans and animals. To carry out optimal lymphatic flow, adequate contractile activity of the lymphatic collectors is necessary. Like in all body systems, aging has also an effect on the lymphatic system. However, limited knowledge is available on how aging directly affects the lymphatic system anatomy, physiology and function. We investigated how senescence leads to alterations in morphology and function of the lymphatic vessels. We used the strategy of a review to summarize the scientific literature of studies that have been published in the area of lymphatic senescence. Searches were carried out on PubMed and Web of Science using predefined search queries. We obtained an initial set of 1060 publications. They were filtered to 114 publications based on strict inclusion and exclusion criteria. Finally, the most appropriate 57 studies that specifically addressed lymphatic senescence have been selected for the preparation of this review. Analysis of the literature showed that lymphatic senescence is associated with alterations in lymphatic muscles and nerve fibers, lymphatic glycocalyx function of lymphatic endothelial cells, effects of chronic ultraviolet light exposure and oxidative stress as well as changes in lymphatic pump, acute inflammation responses and immune function. The current review underscores the relevance of the understudied area of lymphatic senescence. Continued research on the impact of aging on the structure and function of the lymphatic vasculature is needed to provide further insights to develop innovative clinical diagnostic—and treatment—modalities as well as to reduce the morbidity associated with diseases related to the lymphatic system.

Anatomical basis of lymph node detection in gynecologic cancers: a review from a surgical perspective.

Pelvic and para-aortic lymphadenectomy are associated with increased risk of complications and are responsible for a significant proportion of morbidity and impaired quality of life following surgical management of pelvic malignancies. Sentinel lymph node (SLN) was developed as a trade-off between systematic and no lymphadenectomy to limit morbidity while conserving good oncological staging and outcomes. In this comprehensive review, we aimed to synthetize the anatomical basis of the SLN procedure in patients with pelvic malignancies from a surgical perspective. The reliability of the SLN procedure is based on the knowledge of the dissemination pathways for each type of tumors. The most recent understanding of the uterine lymphatic anatomy defined three consistent channels: an upper paracervical pathway (UPP) with draining medial external and/or obturator lymph nodes; a lower paracervical pathway (LPP) with draining internal iliac and/or presacral lymph nodes and the infundibulo-pelvic pathway (IPP) with a course along the fallopian tube and upper broad ligament via the infundibulo-pelvic ligament to its origin. In patients with endometrial cancer, most SLNs are located on the UPP pathway: obturator and external iliac whereas 80% of the SLNs in patients with cervical cancer are located in the external iliac, interiliac and obturator area. Surgical training is a key step toward improving detection rates and exhaustiveness of SLN research while reducing overall morbidity. This is all the more important that the indications for performing complete lymphadenectomy are becoming increasingly rare.

The Deep Lymphatic Anatomy of the Foot

The Deep Lymphatic Anatomy of the Foot

Use of magnetic resonance imaging lymphangiography for preoperative planning in lymphedema surgery: A systematic review.

In recent years, magnetic resonance imaging lymphangiography (MRL) has emerged as a way to predict if patients are candidates for lymphedema surgery, particularly lymphovenous anastomosis (LVA). Our goal was to conduct a systematic review of the literature on the use of MRL for preoperative planning in lymphedema surgery. We hypothesized that MRL could add valuable information to the standard preoperative evaluation of lymphedema patients. On February 17, 2020, we conducted a systematic review of the PubMed/MEDLINE, Cochrane Clinical Answers, and Embase databases, without time frame or language limitations, to identify articles on the use of MRL for preoperative planning of lymphedema surgery. We excluded studies that investigated other applications of magnetic resonance imaging, such as lymphedema diagnosis and treatment evaluation. The primary outcome was the examination capacity to identify lymphatic anatomy and the secondary outcome was the presence of adverse effects. Of 372 potential articles identified with the search, nine studies fulfilled the eligibility criteria. A total of 334 lymphedema patients were enrolled in these studies. Two studies compared MRL findings with those of other standard examinations (indocyanine green lymphography [ICG-L] or lymphoscintigraphy). No adverse effects due to MRL were reported. A study shown that MRL had higher sensitivity to detect lymphatic vessel abnormalities compared with lymphoscintigraphy and a statistically higher chance of successful LVA was observed when the results of MRL agreed with those of ICG-L (p < .001). MRL could be useful for preoperative planning in lymphedema surgery. The scientific evidence has been limited, so further studies with greater numbers of patients and cost analysis are necessary to justify the addition of MRL to current preoperative protocols.

Liver lymphatic drainage patterns follow segmental anatomy in a murine model

The liver’s cellular functions are sustained by a hierarchical, segmentally-organized vascular system. Additionally, liver lymphatic vessels are thought to drain to perihepatic lymph nodes. Surprisingly, while recent findings highlight the importance of organ-specific lymphatics, the functional anatomy of liver lymphatics has not been mapped out. In literature, no segmental or preferential lymphatic drainage patterns are known to exist. We employ a novel murine model of liver lymphangiography and in vivo microscopy to delineate the lymphatic drainage patterns of individual liver lobes. Our data from blue dye liver lymphangiography show preferential lymphatic drainage patterns: Right lobe mainly to hepatoduodenal ligament lymph node 1 (LN1); left lobe to hepatoduodenal ligament LN1 + LN2 concurrently; median lobe showed a more variable LN1/LN2 drainage pattern with increased (sometimes exclusive) mediastinal thoracic lymph node involvement, indicating that part of the liver can drain directly to the mediastinum. Upon ferritin lymphangiography, we observed no functional communication between the lobar lymphatics. Altogether, these results show the existence of preferential lymphatic drainage patterns in the murine liver. Moreover, this drainage can occur directly to mediastinal lymph nodes and there is no interlobar lymphatic flow. Collectively, these data provide the first direct evidence that liver lymphatic drainage patterns follow segmental anatomy.

A preliminary observational study on the vascular, nerve, and lymphatic anatomy and histology of the labia minora from cadaveric and surgical samples.

To better understand details of the fine anatomy of the labia minora, present images of the vascular anatomy and characterize the nerve and lymphatic distribution of the labia minora. Two fixed and five fresh cadaveric specimens were perfused and dissected, and the vascular network was photographed. Labia minora samples, prepared from cadavers, and tissue resulting from labia reduction surgery underwent hematoxylin and eosin staining and S100 and D2-40 immunohistochemical staining. Arteries emanated from the base to the edge of the labia minora, where there was a larger feeding artery, and the arteries were anastomosed. The veins formed anastomotic branches in the same direction as the edge of the labia minora. Arteries and veins that accessed the labia minora were successfully perfused at the same time with no obvious association. Sensory nerve endings were abundant, mostly larger with myelinated nerve trunks and Schwann cells in the central area with suggested neurovascular associations and smaller with no obvious aggregation at the edge. The medial area had 23.63 ± 11.82 nerves/view, the lateral area 21.30 ± 11.49 nerves/view (P > 0.05). The thickest nerve bundle was 3.16 ± 1.41mm from the medial epidermis and 3.13 ± 1.47mm from the lateral epidermis. Lymphatic vessels showed no obvious regional distribution. Labia minora were 21.77 ± 5.69mm wide with 252.87 ± 63.01 lymphatic vessels at 3.67 ± 1.61/mm2 density. The shortest inner diameter of dilated lymphatic vessels was 161.09 ± 49.99 μm. A larger feeding artery exists in the labia minora, which should be noticed in the pre-surgery design of labiaplasty. No difference was observed in the nerve distribution between the medial and lateral sides. Lymphedema might not be the cause of labial hypertrophy.

Degradation of lymphatic anatomy and function in early venous insufficiency

ObjectiveWe used near-infrared fluorescence lymphatic imaging in a pilot study to assess the lymphatics in preulcerative (C2-C4) venous insufficiency and determine whether involvement and/or degradation of lymphatic anatomy or function could play a role in the progression of chronic venous insufficiency. We also explored the role of lymphatics in early peripheral arterial disease. MethodsAfter informed consent and intradermal injections of indocyanine green for rapid lymphatic uptake, near-infrared fluorescence lymphatic imaging was used to assess the lymphatic anatomic structure and quantify the lymphatic propulsion rates in subjects with early venous insufficiency. The anatomic observations included interstitial backflow, characterized by the abnormal spreading of indocyanine green from the injection site primarily into the surrounding interstitial tissues; dermal backflow, characterized by the retrograde movement of dye-laden lymph from collecting lymphatics into the lymphatic capillaries; and lymphatic vessel segmentation and dilation. ResultsTen subjects with venous insufficiency were enrolled, resulting in two legs with C2 disease, nine legs with C3 disease, eight legs with C4 disease, and one leg with C5 disease. Interstitial and/or dermal backflow were observed in 25%, 33%, and 41% of the injection sites in each limb with C2, C3, and C4 disease, respectively. Distinct vessel segmentation and dilation were observed in limbs with a C3 and higher classification, and dermal backflow proximal to the injection sites was observed in two legs with C4 disease and in the inguinal region of the C5 study subject. The overall average lymph propulsion rates were 1.3 ± 0.4, 1.2 ± 0.7, and 0.8 ± 0.5 contractile events/min for limbs with C2, C3, and C4 disease, respectively. One subject with peripheral arterial disease, who had previously undergone bypass surgery, presented with extensive dermal backflow and lymphatic reflux. ConclusionsNear-infrared fluorescence lymphatic imaging demonstrated that, compared with normal health subjects, the lymphatic anatomy and contractile function generally degrade with the severity of venous insufficiency. Lymphatic abnormalities mimic those in early cancer-acquired lymphedema subjects, as previously observed by us and others. Additional studies are needed to decipher the relationship, including any causality, between lymphatic dysfunction and peripheral vascular disease and venous insufficiency.

Anatomical characterization of the inguinal lymph nodes using microcomputed tomography to inform radical inguinal lymph node dissections in penile cancer.

Radical inguinal lymph node dissections (rILND) for penile cancer risk significant postoperative lymphocele and lymphedema. However, reducing the risk of lymphatic complications is limited by our understanding of lymphatic anatomy. Therefore, this study aims to elucidate the lymphatic anatomy within the current surgical borders of a rILND. To visualize the position of the lymph nodes, tissue packets excised from the inguinal region of five fresh, male cadavers were imaged using microcomputed tomography (µCT). To standardize the position, rotation and size between specimens, each lymph node packet was aligned using a Generalized Procrustes analysis. There was a median of 13.5 lymph nodes (range = 8-18) per packet, with the majority (99%) clustered within a 6 cm radius of the saphenofemoral junction; a region 39%-41% smaller than current surgical borders. No difference existed between the number of nodes between sides, or distribution around the saphenofemoral junction. This study provides the first 3D, in situ, standardized characterization of lymph node anatomy in the inguinal region using µCT. By using knowledge of the normal lymphatic anatomy, this study can help inform the reduction in borders of rILND to limit disruption and ensure a complete lymphadenectomy.

Prevention and Treatment of Posttraumatic Lymphedema by Soft Tissue Reconstruction With Lymphatic Vessels Free Flap: An Observational Study.

Extremities soft tissue damage may increase the risk of presenting posttraumatic lymphedema. This type of lymphedema is often ignored in trauma and reconstructive literature. We propose a microsurgical soft tissue reconstruction approach to prevent and/or treat posttraumatic lymphedema. This is a multicentric retrospective observational study. Primary and secondary end points were to prevent and/or treat posttraumatic lymphedema and to achieve a stable soft tissue coverage, respectively. Patients with posttraumatic lymphedema and functional lymphatic channels in the indocyanine green lymphography, and patients with acute soft tissue trauma with lymphatic damage without lymphedema, either to treat and prevent lymphedema, respectively, were included as candidates for soft tissue reconstruction using a superficial circumflex iliac artery perforator lymphatic vessels free flap (SCIP-LV). Patients with no pitting edema, fibrosis, or nonfunctional lymphatics channels were excluded. The inguinal lymphatic anatomy was studied with indocyanine green lymphography for designing and in-setting the flap. Eleven patients underwent to microsurgical reconstruction with SCIP-LV free flap; minimum follow-up was 12 months. There were no flap failures. In the posttraumatic lymphedema group, the mean reduction of excess volume was 63.01%. Quality of life improved 51.85%. No patients in the acute trauma group developed lymphedema after the preventive microsurgical approach. Soft tissue reconstruction with SCIP-LV free flap is an effective approach to prevent and treat posttraumatic lymphedema.

Lymphatic Anatomy and Physiology.

Lymphatics have long been overshadowed by the remainder of the circulatory system. Historically, lymphatics were difficult to study because of their small and indistinct vessels, colorless fluid contents, and limited effective interventions. However, the past several decades have brought increased funding, advanced imaging technologies, and novel interventional techniques to the field. Understanding the history of lymphatic anatomy and physiology is vital to further realize the role lymphatics play in most major disease pathologies and innovate interventional solutions for them.

Quantification of Thoracic Lymphatic Flow Patterns Using Dynamic Contrast-enhanced MR Lymphangiography.

Background Dynamic contrast material-enhanced MR lymphangiography has recently emerged as a technique to image the lymphatic anatomy and identify lymphatic flow abnormalities; however, a method to quantify lymphatic flow in health and disease is needed. Purpose To develop a method to quantify thoracic lymphatic flow patterns using dynamic contrast-enhanced MR lymphangiography. Materials and Methods The following patients with dynamic contrast-enhanced MR lymphangiography images collected in 2015 and 2016 were retrospectively identified: group A, neonates with chylothorax; group B, children with heart failure complicated by plastic bronchitis; and group C, adults with lymphatic plastic bronchitis and without heart failure. An automated image segmentation method was developed for segmenting the contrast-enhanced lymphatic flow in spatiotemporal domains from the dynamic contrast-enhanced MR lymphangiography images. The lymphatic flow rates were quantified for individual patients on the basis of their spatiotemporal dynamic contrast-enhanced MR lymphangiography segmentation results, and the flow rates were compared among the three patient groups by using Wilcoxon rank sum tests. Results Twenty-two patients were evaluated: seven neonates (mean age, 49 days ± 71 [standard deviation]; three boys, four girls), 10 children (mean age, 8 years ± 3; seven boys, three girls), and five adults (mean age, 46 years ± 10; three men, two women). The proposed method was used to obtain lymphatic flow segmentation results with Dice scores of 0.80, 0.82, and 0.83 for patients from groups A, B, and C, respectively. The mean flow rates for groups A, B, and C were 1.8 mL/min ± 1.4, 4.0 mL/min ± 1.8, and 12.5 mL/min ± 3.8, respectively. The flow rate differed significantly between groups A and B (P = .002), groups A and C (P = .01), and groups B and C (P = .01). Conclusion An automatic spatiotemporal segmentation method was used to determine thoracic lymphatic flow rates in individual patients based on their dynamic contrast-enhanced MR lymphangiographic images. © RSNA, 2020 Online supplemental material is available for this article.

Anatomical Characterization of the Inguinal Lymph Nodes Using Micro‐Computed Tomography to Inform Radical Inguinal Lymph Node Dissections for Metastatic Penile Cancer

Background, Rationale &amp; AimIn men with penile cancer, a radical inguinal lymph node dissection (rILND) is integral to prevent metastasis and improve disease specific survival. Unfortunately, lymphocele and lymphedema are severe post‐surgical complications that are common to this procedure. The development of a modified inguinal lymph node dissection, that greatly reduced the amount of lymphatic resection, was effective at reducing the incidence of lymphedema and lymphocele; however, it was not suited for patients with advanced‐stage disease as it risked an incomplete cancer resection. As such, there exists a clinical need for a novel surgical template ‐ informed by the lymphatic anatomy ‐ to reduce these post‐surgical complications while ensuring a thorough cancer resection. However, the lymphatic anatomy of the inguinal region is not well characterized in the literature, with no definitive location or number of lymph nodes reported. Therefore, this study aims to elucidate the lymphatic anatomy within the current surgical borders of a rILND using human cadavers.MethodologyTo visualize the position of the lymph nodes, tissue packets excised from the inguinal region were imaged using micro‐computed tomography (μCT; 154 μm Locus Ultra CT scanner). To characterize the distribution of lymph nodes within each tissue packet, lymph nodes were segmented by grayscale values in 3D using a modified seed‐growing algorithm (Region Growing v1.5; Kellner, 2011) in MATLAB. To compare anatomy between tissue packets, the segmented lymph nodes were aligned (registered) with one another by translating, scaling, rotating, and mirroring (if necessary) such that they were all superimposed in a common coordinate system. This was achieved using a specimen‐specific transformation matrix that was obtained from a generalized Procrustes analysis performed using the positions of four landmarks from each specimen; the anterior superior iliac spine, pubic tubercle, sapheno‐femoral junction, and sartorius as it crosses the femoral artery. These landmarks were chosen due to their consistency between individuals as well as their use as surgical landmarks.ResultsPreliminary findings from five samples (n=3 cadavers) show a median of 6 lymph nodes (range = 3–7); their anatomical distribution is illustrated in Figure 1. In addition to obtaining more specimens, ongoing work focuses on segmentation of structures in this region, such as saphenous vein and the sartorius muscle, to provide spatial context to the identified lymph node distribution.Significance &amp; ImplicationsThis study provides the first standardized comparison of lymph node anatomy in the inguinal region, and utilizes a novel imaging methodology validated by our lab to study the anatomy of lymphatic tissue in 3D and in situ. In doing so, the anatomy elucidated in this study will help inform refinement to the borders of the radical surgical template, to limit unnecessary resection in an attempt to reduce the incidence of post‐surgical lymphedema and/or lymphocele.The standardized lymph node data after having the generalized Procrustes analysis applied. The dotted lines represent the rILND surgical borders.Figure 1

An Innovative Approach For Demonstrating the Lymphatic System in the Gross Anatomy Laboratory

INTRODUCTIONFrom a gross anatomy perspective, the lymphatic system is difficult for students to observe and comprehend in the laboratory setting. Aside from the thoracic duct and spleen, many lymphatic structures are not often preserved well in embalmed cadavers or are damaged or destroyed during the dissection process. This presentation describes an intervention that was created to enhance gross anatomy learning of the lymphatic system.AIM To describe a case‐based anatomy laboratory approach that engages students and emphasizes the clinical relevance of gross anatomic knowledge of the lymphatic system.INSTRUCTIONAL METHODGross anatomy at Western Michigan University Homer Stryker MD SOM (WMed) is prosection‐based and taught within an integrated systems‐based curriculum. The laboratory session covering the lymphatic system occurs during the Immunology and Infectious Disease course. Organization of the session uses a combination of guided and cooperative learning techniques.Student anatomy groups (6 students/group) progress through 7 cadaver stations, each having an associated clinical case. The cases encompass a variety of cancers, infections, and traumatic injuries to lymphatic system structures. At each station, students must identify the normal structures involved in the clinical scenario. In addition, students pin on the cadavers the location of lymph node groups that would likely be enlarged and/or need to be biopsied based on patient presentation and diagnoses. Cases also include short‐answer clinical application questions. Students within their groups work independently to identify and pin structures and compose their short answers. During the session, faculty circulate throughout the lab to confirm student answers and provide additional information when necessary.RESULTSPrior to this innovation, student feedback was below average and many students had difficulty seeing the relevance of the laboratory session. Since flipping the approach, evaluations have improved. Student comments expressing frustration over not being able to observe structures decreased. The number of comments expressing confusion about the purpose of the laboratory session and questioning if it is an effective use of time has also been reduced.DISCUSSION AND CONCLUSIONThis approach highlights the importance of the lymphatic system which is often overlooked in the gross anatomy laboratory. It provides faculty with a useful tool to help students see the clinical relevance of lymphatic gross anatomy and how this knowledge is applicable to physical examination and patient evaluation.Support or Funding InformationThere is no external funding for this project.