Impaired lymphatic function recovered after great saphenous vein stripping in patients with varicose vein: venodynamic and lymphodynamic results

Imaging peripheral lymphatic dysfunction in chronic conditions

The lymphatics play important roles in chronic diseases/conditions that comprise the bulk of healthcare worldwide. Yet the ability to routinely image and diagnose lymphatic dysfunction, using commonly available clinical imaging modalities, has been lacking and as a result, the development of effective treatment strategies suffers. Nearly two decades ago, investigational near-infrared fluorescence lymphatic imaging and ICG lymphography were developed as routine diagnostic for clinically evaluating, quantifying, and treating lymphatic dysfunction in cancer-related and primary lymphedema, chronic venous disease, and more recently, autoimmune and neurodegenerative disorders. In this review, we provide an overview of what these non-invasive technologies have taught us about lymphatic (dys) function and anatomy in human studies and in corollary animal studies of human disease. We summarize by commenting on new impactful clinical frontiers in lymphatic science that remain to be facilitated by imaging.

Review on the Lymphatic Vessels in the Dental Pulp

Simple Summary

It is debatable whether lymphatic vessels exist in the dental pulp. Most researchers confirm their presence; however, the lymphatic system in the dental pulp is much less developed compared to other tissues of the body. Lymphangiogenesis occurs in the dental pulp with inflammatory changes as a response to inflammatory stimuli acting on the tooth. If lymphangiogenesis is defined as the development of lymphatic vessels from already existing ones, such a mechanism is possible only when lymphatic vessels are present in healthy teeth. Research papers have not conclusively proved whether lymphatic vessels can form in the dental pulp. The use of an immunohistochemical examination can very likely prove the presence of a lymphatic system in dental tissues. However, the evaluation of the lymphatic system of the teeth is problematic because it is quite difficult to clearly distinguish lymphatic vessels from small blood vessels.

Abstract

Despite many studies, opinions on the lymphatic system of the teeth are still incompatible. Studies using light and electron microscopy and directly using methods such as a radioisotope (radionuclide) scan and interstitial fluid pressure measurement reported incomplete results. Immunohistochemistry (IHC) plays the main role in investigating presence of the lymphatic system in dental tissues. This method uses labeled antibodies against antigens typical of lymphatic vessels. The use of appropriate staining enables the detection of antigen-antibody reaction products using a light (optical), electron or fluorescence microscope. However, these studies do not show the system of vessels, their histologic structure under physiological conditions and inflammation as well as the lymphangiogenesis process in the dental pulp. Unfortunately, there is a lack of studies associating the presence of lymphatic vessels in the dental pulp with local lymphatic nodes or large vessels outside the tooth. In the scientific and research environment, the evaluation of the lymphatic system of the teeth is problematic because it is quite difficult to clearly distinguish lymphatic vessels from small blood vessels. Despite many indications of the presence of lymphatic vessels in the pulp chamber, this problem remains open and needs further research.

Combined Lymphovenous Anastomosis and Great Saphenous Vein Stripping for Comorbid Lymphedema and Varicose Veins

Introduction: Treatment for patients with comorbid lymphedema and varicose veins is controversial. Surgical options for these patients are limited. The study was aimed to investigate the validity of combined lymphovenous anastomosis (LVA) and great saphenous vein stripping (GSVS) for comorbid lymphedema and varicose veins. Patients and Methods: Thirteen patients were involved in the study, and the detail was 21 edematous lower limbs (with coexisting varicose veins and lymphedema; the varicose vein and lymphedema [VL] group) who underwent combined GSVS and LVA therapy. Fifteen patients (with 30 edematous lower limbs and lymphedema only; the lymphedema [L] group) who underwent LVA only were included as a control group. GSVS was performed before LVA in the VL group. Results: No significant differences were seen between the groups at baseline. There were no cases indocyanine green (ICG) lymphography pattern deteriorated after GSVS. No significant difference was seen in lymphatic detection rate; 129.71% ± 58.27% (67%-333%) in the VL group and 122.27% ± 39.47% (50%-250%) in the L group (p = 0.59 > 0.05), respective lymphatic diameters 0.66 ± 0.13 (0.45-0.9) mm and 0.75 ± 0.17 (0.45-1.0) mm (p = 0.07 > 0.05), and respective lymphedema improvement rate 12.17% ± 7.35% (0%-27.4%) and 12.65% ± 7.43% (3.7%-22.3%) (p = 0.86 > 0.05). Discussion: In this study, stripping surgery does not cause lymphatic impairment, at least to the extent that would impede the success of an LVA procedure. Comorbid varicose veins and lymphedema can be treated surgically by a combination of LVA and GSVS.

A Novel Approach to Quantifying Lymphatic Contractility during Indocyanine Green Lymphangiography

Lymphedema arises from impaired lymphatic function. Quantification of lymphatic contractility has previously been shown using a custom-built near-infrared imaging system. However, to broaden the clinical use of functional lymphatic measurements, these measurements need to be performed using a standard-of-care, clinically available camera. The authors propose an objective, algorithmic, and clinically accessible approach to quantify lymphatic contractility using a 3-minute indocyanine green lymphangiograph recorded with a commercially available near-infrared camera. A retrospective review of the authors' indocyanine green lymphangiography video repository maintained in a Research Electronic Data Capture database was performed. All patients with a newly diagnosed unilateral breast cancer undergoing preoperative indocyanine green lymphangiography were included in the analysis. Patient medical records were then analyzed for patient demographics, and videos were analyzed for contractility. Seventeen consecutive patients with unilateral breast cancers underwent video processing to quantify lymphatic contractility of the ipsilateral extremity in contractions per minute. All patients were women, with an average age of 60.5 years (range, 38 to 84 years). The average lymphatic contractility rate was 1.13 contractions per minute (range, 0.67 to 2.5 contractions per minute). Using a clinically accessible standard-of-care device for indocyanine green lymphangiography, the authors were able to determine lymphatic contractility rates of a normal extremity. The authors' finding falls within the range of previously published data quantifying lymphatic contractility using a research device, suggesting that the authors' technique provides a clinically accessible, time-effective means of assessing lymphatic contractility. Potential future applications include both lymphedema surveillance and evaluation of nonsurgical and surgical interventions. CLINICAL QUESTION/LEVEL OF EVIDENCE:: Diagnostic, IV.

Reduced Lymphatic Function Predisposes to Calcium Channel Blocker Edema: A Randomized Placebo-Controlled Clinical Trial

Background: The current belief is that the calcium channel blocker (CCB)-induced edema is due to a preferential arterial over venous dilatation leading to increased fluid filtration. We challenged this conviction by measuring the lymphatic removal of interstitial fluid during chronic systemic treatment with the CCB, amlodipine. Lymphatic vessels could potentially be an off-target effect of the drugs and play a role in CCB edema. Methods and Results: Sixteen healthy postmenopausal women completed a 12-week double-blinded randomized placebo-controlled crossover trial. Lymphatic function was assessed by near-infrared fluorescence imaging. The lymphatic function during amlodipine treatment compared with placebo did not show any difference in pumping pressure (53.9 ± 13.9 mmHg vs. 54.7 ± 9.4 mmHg, p = 0.829), contraction frequency (0.4 ± 0.2/min vs. 0.4 ± 0.3/min, p = 0.932), refill time (440 ± 438 seconds vs. 442 ± 419 seconds, p = 0.990), or propagation velocity of lymph packets (18 ± 10 mm/s vs. 15 ± 7 mm/s, p = 0.124). However, the subjects who developed edema during CCB treatment had a 20% lower baseline lymphatic pumping pressure (48.9 ± 4.4 mmHg, n = 7) than the subjects not affected by treatment (59.1 ± 1.2 mmHg, n = 9, p = 0.025). Contraction frequency, refill time, and lymph packet velocity showed no differences in baseline values between the two groups. Conclusion: Our results suggest that CCB does not directly impair lymphatic function. However, our results show that a reduced lymphatic function predisposes to CCB edema, which may explain why some patients develop edema during treatment.

Lymphatic flow restoration after stripping surgery for varicose veins: A case report

It has been suggested that the dynamics of the venous and lymphatic systems interact as a mutually dependent dual outflow system and that derangement of lymph flow could be reversed by surgical treatment of venous incompetence. In this report, we describe a patient in whom lymphatic function was restored after stripping of the great saphenous vein for varicosity. The patient was a 79-year-old woman who had varicose veins along the medial side of an edematous left leg. Lymphatic function was investigated using indocyanine green imaging to evaluate for the presence of lymphedema. Based on the findings, we made a diagnosis of bilateral varicosity of the great saphenous vein with left-sided lymphedema. The great saphenous vein was stripped between the groin and ankle on both sides. At 3 months after the stripping procedure, lymphatic flow was observed immediately after injection of indocyanine green in both legs along the medial side from the foot to the groin. We therefore determined that lymphatic flow had been restored after the stripping surgery. The functions of the venous and lymphatic systems are thought to be closely related, and that, if the function of one declines, the other will also be affected. Treatment of venous system, including stripping, may help to break the vicious cycle of lymphatic stasis and venous insufficiency.

Fluoreszenz-Lymphographie

Der fluoreszierenden Farbstoff Indocyaningrün ermöglicht es uns, in Verbindung mit einer Infrarotkamera den Lymphabfluss zu beurteilen, den Sentinel-Lymphknoten zu entdecken, in neuen Operationstechniken die Funktionsfähigkeit der Lymphgefäße zu beurteilen, sowie die Wirksamkeit alter und neuer Behandlungsmethoden zu erkennen.

Insufficient Lymph Drainage Causes Abnormal Lipid Accumulation and Vein Wall Degeneration

Objective: Previously, we analyzed human varicose veins (VV) using imaging mass spectrometry (IMS) and detected the abnormal accumulation of lipid molecules in the walls of VV, possibly due to insufficient lipid drainage by the lymphatic vessels. In this study, we created an animal model of lymphatic insufficiency to investigate the effects of insufficient lymph drainage on vein walls. Methods: In rats, the lymphatic collecting vessels surrounding the femoral vein were ligated on one side (the model tissue), which caused the local retention of lymphatic fluid in the perivascular tissue. The equivalent contralateral tissue was used as a control. A histological study of the femoral vein and the surrounding perivascular tissue was conducted. IMS was used to analyze the distribution of lipid molecules in the perivascular tissue. Results: Fourteen days after the procedure, the lymphatic vessels in the model tissue were significantly dilated. Furthermore, IMS revealed that the composition of the lipid molecules in the perivascular regions of the model tissue had altered. Compared with the control tissue, the model tissue exhibited marked perivascular accumulation of lysophosphatidylcholine (1-acyl 16:0), phosphatidylcholine (16:0/20:4), and triglycerides (52:2). Interestingly, the walls of the femoral veins running through the model tissue were 3.4-fold thicker than those of the femoral veins running through the control tissue. The number of tumor necrosis factor α-positive adipocytes was increased in the perivascular regions of the model tissue. Conclusion: The findings of this study indicated that the accumulation of lymphatic fluid due to insufficient lymph drainage changes the structure of vein walls, and such changes might be associated with chronic venous insufficiency. (This is a translation of Jpn J Phlebol 2015; 26: 227-235.).

Lymphatic dysfunction after ligation surgery for varicose vein

Objective:

Although the lymphatic complications such as lymphocele sometimes occur after surgery for varicose veins, the lymphatic function of such patients has not been evaluated. In this case report, we present a case of lymphocele after ligation surgery for varicose vein. We also detected subclinical dysfunction in lower limb using indocyanine green (ICG) lymphography.

Case report:

A 76 year- old female underwent ligation surgery for right lower leg varicose vein, and she noticed the squashy lesion in the medial side of the right knee. Three years later, she consulted our clinic and we performed ICG lymphography. We observed dermal backflow around the mass, which indicated lymphatic dysfunction. After injecting additional ICG around the knee, we punctured and drained the clear, yellow fluid from the mass and it was contrasted with ICG during the examination and the involvement of the lymphatic system was proven.

A review of performance of near-infrared fluorescence imaging devices used in clinical studies

Near-infrared fluorescence (NIRF) molecular imaging holds great promise as a new "point-of-care" medical imaging modality that can potentially provide the sensitivity of nuclear medicine techniques, but without the radioactivity that can otherwise place limitations of usage. Recently, NIRF imaging devices of a variety of designs have emerged in the market and in investigational clinical studies using indocyanine green (ICG) as a non-targeting NIRF contrast agent to demark the blood and lymphatic vasculatures both non-invasively and intraoperatively. Approved in the USA since 1956 for intravenous administration, ICG has been more recently used off label in intradermal or subcutaneous administrations for fluorescence imaging of the lymphatic vasculature and lymph nodes. Herein, we summarize the devices of a variety of designs, summarize their performance in lymphatic imaging in a tabular format and comment on necessary efforts to develop standards for device performance to compare and use these emerging devices in future, NIRF molecular imaging studies.

Neurotoxic effects of indocyanine green -cerebellar granule cell culture viability study

The aim of this study was to examine neurotoxicity indocyanine green (ICG). We assessed viability of primary cerebellar granule cell culture (CGC) exposed to ICG to test two mechanisms that could be the first triggers causing neuronal toxicity: imbalance in calcium homeostasis and the degree of oligomerization of ICG molecules. We have observed this imbalance in CGC after exposure to 75-125μΜ ICG and dose and application sequence dependent protective effect of Gadovist on surviving neurons in vitro when used with ICG. Spectroscopic studies suggest the major cause of toxicity of the ICG is connected with oligomers formation. ICG at concentration of 25 μM (which is about 4 times higher than the highest concentration of ICG in the brain applied in in-vivo human studies) is not neurotoxic in the cell culture.

[Treatment of varicose veins and limb lymphedema]

Two questions arise when considering the treatment of varicose veins and the development of lymphedema: can the treatment cause lymphedema? Can it worsen it? Primary lymphedema is rarely associated with varicose veins except in the lymphedema-distichiasis syndrome. Data available in the literature is essentially based on surgical treatment. Stripping on a normal limb may induce chronic lymphedema in almost 0.1% of cases. The risk of lymphedema after stripping in patients with previous pelvic surgery including lymph node excision and/or radiotherapy remains unknown. In patients with lower limb lymphedema wearing strong elastic compression stockings, stripping provides little clinical improvement and can worsen volume. The main objective is also to avoid venous complications. Lymphatic lesions related to stripping can be evaluated by lymphography or lymphoscintigraphy. New techniques for treating varicose veins (sclerotherapy, endovenous laser treatment, radiofrequency ablation) seem to induce fewer lymphatic complications. Further studies are required to confirm these results. Indications for treatment should be unquestionable and patients must be alerted to the potential risk of lymphedema or its worsening.

An experimental lymphoscintigraphy study in an acute unilateral deep venous thrombosis model

BACKGROUND

The aim of this study is to investigate the effect of both inguinal exploration and deep venous thrombosis on lymphatic flow in an experimental model of unilateral acute obstruction of the femoral vein.

METHODS AND RESULTS

Eighteen male New Zealand White rabbits were the subjects of this study. The rabbits were divided into three groups; Group 1 (n=6, control), Group 2 (n=6, sham), and Group 3 (n=6, operation). After the lymphoscintigraphy was performed on the Group 1 animals, the rabbits in Group 2 and Group 3 underwent intervention. In Group 3, the femoral vein was clipped and excised. In Group 2, an inguinal incision was performed and the clip materials were placed beneath the femoral vein. After the surgical intervention, lower extremity lymphoscintigraphy by subcutaneous administration of Tc-99m nanocolloid was performed in dynamic and static manner in Groups 2 and 3 on the second, fifteenth and thirtieth days after the operation. Unilateral impairment of the lymphatic flow in the operated extremity was observed in Group 3 in the early and late postoperative period but unilateral lymphatic impairment was observed in Group 2 in only the late postoperative period.

CONCLUSION

The lymphatic impairment in an operated extremity might be the consequence of surgical intervention rather than acute venous obstruction in cases where both situations are observed.

Identification of interstitial Cajal-like cells in the human thoracic duct

Interstitial Cajal-like cells (ICLCs) are speculated to be pacemakers in smooth muscle tissues. While the human thoracic duct (TD) is spontaneously active, the origin of this activity is unknown. We hypothesized that ICLCs could be present in the TD and using histological techniques, immunohistochemistry and immunofluorescence we have investigated the presence of ICLCs, protein markers for ICLCs and the cellular morphology of the human TD. Transmission electron microscopy was employed to investigate ultrastructure. Methylene blue staining, calcium-dependent fluorophores and confocal microscopy were used to identify ICLCs in live tissue. Methylene blue stained cells with morphology suggestive of ICLCs in the TD. Immunoreactivity localized the ICLC protein markers c-kit, CD34 and vimentin to many cells and processes associated with smooth muscle cells (SMCs): coexpression of c-kit with vimentin or CD34 was observed in some cells. Electron microscopy analysis confirmed ICLCs as a major cell type of the human TD. Lymphatic ICLCs possess caveolae, dense bands, a patchy basal lamina, intermediate filaments and specific junctions to SMCs. ICLCs were ultrastructurally differentiable from other interstitial cells observed: fibroblasts, mast cells, macrophages and pericytes. Lymphatic ICLCs were localized to the subendothelial region of the wall as well as in intimate association with smooth muscle bundles throughout the media. ICLCs were morphologically distinct with multiple processes and also spindle shapes. Confocal imaging with calcium-dependent fluorophores corroborated cell morphology and localization observed in fixed tissues. Lymphatic ICLCs thus constitute a significant cell type of the human TD and physically interact with lymphatic SMCs.

Imaging tumor-induced sentinel lymph node lymphangiogenesis with LyP-1 peptide

Lymphangiogenesis in tumor-draining lymph nodes (LNs) starts before the onset of metastasis and is associated with metastasis to distant LNs and organs. In this study, we aimed to visualize tumor-induced lymphangiogenesis with a tumor lymphatics-specific peptide LyP-1. The LyP-1 peptide was labeled with a near-infrared fluorophore (Cy5.5) for optical imaging. At days 3, 7, 14 and 21 after subcutaneous 4T1 tumor inoculation, Cy5.5-LyP-1 was administered through the middle phalanges of the upper extremities of the tumor-bearing mice. At 45 min and 24 h postinjection, brachial LN fluorescence imaging was performed. Ex vivo fluorescence images were acquired for quantitative analysis of the fluorescence intensity. Tumor-induced lymphangiogenesis was confirmed by LYVE-1 immunostaining and increased size of tumor side brachial LNs. Cy5.5-LyP-1 staining in LNs co-localized with LYVE-1, suggesting lymphatics-specific binding of LyP-1 peptide. The brachial LNs were clearly visualized by optical imaging at both time points. The tumor side LNs showed significantly higher fluorescence intensities than the contralateral brachial LNs at days 7, 14, and 21, but not day 3 after tumor inoculation. At day 21 after tumor inoculation, the average signal of tumor-draining LNs was 78.0±2.44, 24.3±5.43, 25.6±0.25 (×10(3) photon/cm2/s) using Cy5.5-LyP-1, Cy5.5-LyP-1 with blocking, and Cy5.5 only, respectively. Tumor-draining brachial LNs showed extensive growth of lymphatic sinuses throughout the cortex and medulla. Use of LyP-1 based imaging probes with optical imaging offers a useful tool for the study of tumor-induced lymphangiogenesis. LyP-1 may serve as a marker of lymphangiogenesis useful in detecting "high risk" LNs before tumor metastasis and after micro-metastasis, as well as for screening potential anti-lymphatic therapies.

Translation of near-infrared fluorescence imaging technologies: emerging clinical applications

Technical developments in near-infrared fluorescence (NIRF) imaging and tomography have enabled recent translation into investigational human studies. Noninvasive imaging of the lymphatic vasculature for diagnosis and assessment of function has been uniquely accomplished with NIR using indocyanine green (ICG), a nonspecific dye that has comparatively poor fluorescent properties compared to emerging dyes. Adjunct use of NIRF-ICG for (a) intraoperative sentinel lymph node mapping for cancer staging, (b) video-angiography during surgery, and (c) discrimination of malignant from benign breast lesions detected by mammography and ultrasongraphy also evidences the clinical utility of NIRF. Future NIRF imaging agents that consist of bright fluorescent dyes conjugated to disease-targeting moieties promise molecular imaging and image-guided surgery. In this review, emerging NIRF imaging is described within the context of nuclear imaging technologies that remain the "gold standard" of molecular imaging.

Engineering the Lymphatic System

The recent advances in our understanding of lymphatic physiology and the role of the lymphatics in actively regulating fluid balance, lipid transport, and immune cell trafficking has been furthered in part through innovations in imaging, tissue engineering, quantitative biology, biomechanics, and computational modeling. Interdisciplinary and bioengineering approaches will continue to be crucial to the progression of the field, given that lymphatic biology and function are intimately woven with the local microenvironment and mechanical loads experienced by the vessel. This is particularly the case in lymphatic diseases such as lymphedema where the microenvironment can be drastically altered by tissue fibrosis and adipocyte accumulation. In this review we will highlight contributions engineering and mechanics have made to lymphatic physiology and will discuss areas that will be important for future research.

Human Lymphatic Architecture and Dynamic Transport Imaged Using Near-infrared Fluorescence

BACKGROUND

Although the importance of lymphatic function is well recognized, the lack of real-time imaging modalities limits our understanding of its role in many diseases. In a phase 0 exploratory study, we used dynamic, near-infrared (NIR) fluorescence imaging to assess the extremes of lymphatic architecture and transport in healthy human subjects and in subjects clinically diagnosed with unilateral lymphedema (LE), a disease that can be prevalent in cancer survivors.

METHODS AND RESULTS

Active lymphatic propulsion was imaged after intradermal injections of 25 µg of indocyanine green (total maximum dose ≤400 µg) bilaterally in the arms or legs of control and subjects. Images show well-defined lymphatic structures with propulsive dye transport in limbs of healthy subjects. In LE subjects, we observed extravascular dye accumulation, networks of fluorescent lymphatic capillaries, and/or tortuous lymphatic vessels in all symptomatic and some asymptomatic limbs. Statistical models indicate that disease status and/or limb significantly affect parameters of apparent lymph propagation velocity and contractile frequency.

CONCLUSIONS

These clinical research studies demonstrate the potential of NIR fluorescence imaging as a diagnostic measure of functional lymphatics and as a new tool in translational research studies to decipher the role of the lymphatic system in cancer and other diseases.

A novel method of measuring human lymphatic pumping using indocyanine green fluorescence lymphography

OBJECTIVES

Lymph transportation through the body is partly controlled by the intrinsic pumping of lymphatic vessels. Although an understanding of this process is important for medical application, little is currently known because it is difficult to measure. Here, we introduce an easy, safe, and cost-effective technique for measuring lymphatic pumping in leg superficial lymphatic vessels. Readings obtained with this technique were compared with values obtained with dynamic lymphoscintigraphy. Differences in lymphatic pumping between healthy volunteers and patients with lymphedema were also investigated.

METHODS

Indocyanine green (ICG) fluorescence lymphography was performed by subcutaneously injecting 0.3 mL of ICG (0.5%) into the dorsum of the foot. Real-time fluorescence images of lymph propulsion were obtained with an infrared-light camera system with the individual supine or sitting. A custom-made transparent sphygmomanometer cuff was wrapped around the lower leg and connected to a standard mercury sphygmomanometer. The cuff was inflated to 60 mm Hg and then gradually deflated at 5-minute intervals to lower the pressure by 10-mm Hg steps until the fluorescence contrast agent exceeded the upper border of the cuff, indicating that the lymphatic contraction had overcome the cuff pressure. Lymph pumping pressure (P(pump)) was defined as the value of the cuff pressure when the contrast agent exceeded the upper border of the cuff. We measured P(pump) among healthy volunteers who maintained a supine position and compared these values with measurements obtained from lymphoscintigraphy. P(pump) values while sitting were also compared between 30 legs from healthy volunteers and 30 legs from lymphedematous patients.

RESULTS

Among healthy, supine participants, P(pump) was 25.2 ± 16.7 mm Hg (mean ± standard deviation [SD]) when measured by ICG fluorescence lymphography. These values were significantly correlated with values taken using dynamic lymphoscintigraphy (r(2) = 0.54, p < .01), while 2 SDs of the mean were approximately 20 mm Hg, suggesting a substantial disagreement between the two methods (Bland-Altman plots). In the comparison of seated measurements, readings for healthy participants (P(pump) = 29.3 ± 16.0) were higher than those for lymphedematous participants (13.2 ± 14.9).

CONCLUSION

ICG fluorescence is an accurate-as well as a safe, easy, and economical-method of measuring lymphatic pumping. Therefore, it may develop as a vital tool for diagnosing lymphatic malfunctions even when they are only in their formative stages. Studies that use this technique may increase our knowledge of the lymphatic system as a whole, allowing us to develop better treatments for lymphatic disorders.

Near-Infrared Fluorescence Imaging in Humans with Indocyanine Green: A Review and Update

Near-infrared (NIR) fluorescence imaging clinical studies have been reported in the literature with six different devices that employ various doses of indocyanine green (ICG) as a non-specific contrast agent. To date, clinical applications range from (i) angiography, intraoperative assessment of vessel patency, and tumor/metastasis delineation following intravenous administration of ICG, and (ii) imaging lymphatic architecture and function following subcutaneous and intradermal ICG administration. In the latter case, NIR fluorescence imaging may enable new discoveries associated with lymphatic function due to (i) a unique niche that is not met by any other conventional imaging technology and (ii) its exquisite sensitivity enabling high spatial and temporal resolution. Herein, we (i) review the basics of clinical NIR fluorescence imaging, (ii) survey the literature on clinical application of investigational devices using ICG fluorescent contrast, (iii) provide an update of non-invasive dynamic lymphatic imaging conducted with our FDPM device, and finally, (iv) comment on the future NIR fluorescence imaging for non-invasive and intraoperative use given recent demonstrations showing capabilities for imaging following microdose administration of contrast agent.