Lymphatic capillary pressure in patients with primary lymphedema

Lymph Flow Before and After Lymphaticovenous Anastomosis Measured Using Transonic Transit-Time Ultrasound Microvascular Flowprobe

Background: Assessment of lymph flow has proven challenging. Transit-time ultrasound technique (TTUT) is the first technique that provides real-time quantitative lymphatic flow values. In cardiothoracic surgery and neurosurgery, this technique has tremendous clinical value in assessing surgery quality and predicting outcomes. The objective of this study was to measure lymph flow before and after lymphaticovenous anastomosis (LVA), using TTUT. Methods and Results: Consecutive patients with peripheral lymphedema undergoing LVA were included. Preoperative workup was performed using indocyanine green (ICG) lymphangiography. Perioperatively, the Transonic^® Microvascular Flowprobe was used to measure lymph flow before and after anastomosis. Twenty-five patients with International Society of Lymphology stage IIA (68%) and stage IIB (32%) peripheral lymphedema were included. Lymph flow velocities ranged from 0.02 to 0.80 mL/min (mean 0.25 ± 0.19) before anastomosis and from 0.02 to 0.86 mL/min (mean 0.27 ± 0.22) after anastomosis (p = 0.340). Mean flow values were significantly higher in the upper extremities compared with the lower extremities. Furthermore, there was a decrease in flow in patients with ICG stage IV in comparison with ICG stage III. Clinical outcomes could not be directly correlated with flow values in these individual cases. Conclusion: TTUT micro-flowprobe is a suitable instrument to measure real-time quantitative lymphatic flow in both lymphatics and LVA. It can confirm patency of lymphatic collectors and LVA peroperatively. Significantly higher lymph flow velocities were found in upper extremities in comparison with lower extremities, both before and after LVA. Further studies should be performed to evaluate lymph flow values and clinical correlation.

Development and Validation of a Risk Model for Breast Cancer-Related Lymphedema

IMPORTANCE

Approximately 1 in 5 patients with breast cancer who undergo axillary lymph node dissection will develop lymphedema. To appropriately triage and monitor these patients for timely diagnosis and treatment, robust risk models are required.

OBJECTIVE

To evaluate the prognostic value of mammographic breast density in estimating lymphedema severity.

DESIGN, SETTING, AND PARTICIPANTS

This prognostic study collected data from July 16, 2018, to March 3, 2020, from the electronic health records of patients of the Cancer Rehabilitation and Survivorship Program at the Princess Margaret Cancer Centre in Toronto, Ontario, Canada. Participants included women who had completed curative treatment for a first diagnosis of breast cancer and who were referred to the program. Also included were a sample of patients in the general breast oncology population who were receiving follow-up care at the center during the same period but who were not referred to the program. All patients attended follow-up appointments at the Princess Margaret Cancer Centre from January 1, 2016, to May 1, 2018. The cohort was randomly split 2:1 to group patients into a training cohort and a validation cohort.

EXPOSURES

Participant demographic and clinical characteristics included age, sex, body mass index (BMI), medical history, cancer characteristics, and cancer treatment.

MAIN OUTCOMES AND MEASURES

Spearman correlation coefficient between measured and predicted volume of lymphedema was calculated. Area under the curve (AUC) values were generated for predicting the occurrence of at least mild lymphedema (volume, >200 mL) and severe lymphedema (volume, >500 mL) at the time of initial lymphedema diagnosis.

RESULTS

A total of 373 female patients (median [interquartile range] age, 52.3 [45.9-60.1] years) were eligible for this analysis. Multivariate linear regression identified 3 patient factors (age, BMI, and mammographic breast density), 1 cancer factor (number of pathological lymph nodes), and 1 treatment factor (axillary lymph node dissection) as independent prognostic variables. In validation testing, Spearman correlation revealed a statistically significant moderate correlation (coefficient, 0.42; 95% CI, 0.26-0.56; P < .001) between measured volume and predicted volume of lymphedema. The AUC values were 0.72 (95% CI, 0.60-0.83) for predicting the occurrence of mild lymphedema and 0.83 (95% CI, 0.74-0.93) for severe lymphedema.

CONCLUSIONS AND RELEVANCE

This prognostic study found that patients with low breast density appeared to be at a higher risk of developing severe lymphedema. The finding suggests that by combining breast density with established risk factors a multivariate linear regression model could be used to predict the development of lymphedema and provide volumetric estimates of lymphedema severity in patients with breast cancer.

Development and Themes of Diagnostic and Treatment Procedures for Secondary Leg Lymphedema in Patients with Gynecologic Cancers

Patients with leg lymphedema sometimes suffer under constraint feeling leg heaviness and pain, requiring lifelong treatment and psychosocial support after surgeries or radiation therapies for gynecologic cancers. We herein review the current issues (a review of the relevant literature) associated with recently developed diagnostic procedures and treatments for secondary leg lymphedema, and discuss how to better manage leg lymphedema. Among the currently available diagnostic tools, indocyanine green lymphography (ICG-LG) can detect dermal lymph backflow in asymptomatic legs at stage 0. Therefore, ICG-LG is considered the most sensitive and useful tool. At symptomatic stage ≥1, ultrasonography, magnetic resonance imaging-lymphography/computed tomography-lymphography (MRI-LG/CT-LG) and lymphosintiography are also useful. For the treatment of lymphedema, complex decongestive physiotherapy (CDP) including manual lymphatic drainage (MLD), compression therapy, exercise and skin care, is generally performed. In recent years, CDP has often required effective multi-layer lymph edema bandaging (MLLB) or advanced pneumatic compression devices (APCDs). If CDP is not effective, microsurgical procedures can be performed. At stage 1–2, when lymphaticovenous anastomosis (LVA) is performed, lymphaticovenous side-to-side anastomosis (LVSEA) is principally recommended. At stage 2–3, vascularized lymph node transfer (VLNT) is useful. These ingenious procedures can help maintain the patient’s quality of life (QOL) but unfortunately cannot cure lymphedema. The most important concern is the prevention of secondary lymphedema, which is achieved through approaches such as skin care, weight control, gentle limb exercises, avoiding sun and heat, and elevation of the affected leg.

Evaluation of an Electro-Pneumatic Device for Artificial Capillary Pulse Generation used in a Prospective Study in Animals for Surgical Neck Wound Healing

The paper examines the development and testing of an electro-pneumatic device for wound healing therapy after surgery in the neck area. The device generates air pressure values in a miniaturized cuff using electronic circuitry to drive an electro-valve and air compressor. The device works in two distinct modes: continuous pressure mode and pulsating pressure mode. The pressure value setting can vary from 3 to 11 mmHg, and the pulsating pressure mode’s operating frequency range is approximately 0.1 to 0.3 Hz. Laboratory measurements were conducted to evaluate the device’s correct functioning in both continuous and pulsating pressure modes. A four-day prospective study with animals (n = 10) was also conducted to evaluate neck wound healing therapy using the electro-pneumatic device. Out of the twelve histological parameters analysed to reveal the differences between the experimental and control wounds, only one demonstrated a significant difference. Out of the ten animals treated with the device, three showed a significant difference in terms of benefit after therapy. We can therefore conclude that the device potentially improves the wound healing process in the neck area if the pre-set air pressure value does not exceed 8 mmHg.

Mechanotransduction in Blood and Lymphatic Vascular Development and Disease

The blood and lymphatic vasculatures are hierarchical networks of vessels, which constantly transport fluids and, therefore, are exposed to a variety of mechanical forces. Considering the role of mechanotransduction is key for fully understanding how these vascular systems develop, function, and how vascular pathologies evolve. During embryonic development, for example, initiation of blood flow is essential for early vascular remodeling, and increased interstitial fluid pressure as well as initiation of lymph flow is needed for proper development and maturation of the lymphatic vasculature. In this review, we introduce specific mechanical forces that affect both the blood and lymphatic vasculatures, including longitudinal and circumferential stretch, as well as shear stress. In addition, we provide an overview of the role of mechanotransduction during atherosclerosis and secondary lymphedema, which both trigger tissue fibrosis.

Prominent Lymphatic Vessel Hyperplasia with Progressive Dysfunction and Distinct Immune Cell Infiltration in Lymphedema

Lymphedema is a common complication that occurs after breast cancer treatment in up to 30% of the patients undergoing surgical lymph node excision. It is associated with tissue swelling, fibrosis, increased risk of infection, and impaired wound healing. Despite the pronounced clinical manifestations of the disease, little is known about the morphological and functional characteristics of the lymphatic vasculature during the course of lymphedema progression. We used an experimental murine tail lymphedema model where sustained fluid stasis was generated on disruption of lymphatic flow, resulting in chronic edema formation with fibrosis and adipose tissue deposition. Morphological analysis of the lymphatic vessels revealed a dramatic expansion during the course of the disease, with active proliferation of lymphatic endothelial cells at the early stages of lymphedema. The lymphatic capillaries exhibited progressively impaired tracer filling and retrograde flow near the surgery site, whereas the collecting lymphatic vessels showed a gradually decreasing contraction amplitude with unchanged contraction frequency, leading to lymphatic contraction arrest at the later stages of the disease. Lymphedema onset was associated with pronounced infiltration by immune cells, predominantly Ly6G(+) and CD4(+) cells, which have been linked to impaired lymphatic vessel function.

Intrinsic increase in lymphangion muscle contractility in response to elevated afterload

Collecting lymphatic vessels share functional and biochemical characteristics with cardiac muscle; thus, we hypothesized that the lymphatic vessel pump would exhibit behavior analogous to homeometric regulation of the cardiac pump in its adaptation to elevated afterload, i.e., an increase in contractility. Single lymphangions containing two valves were isolated from the rat mesenteric microcirculation, cannulated, and pressurized for in vitro study. Pressures at either end of the lymphangion [input pressure (P(in)), preload; output pressure (P(out)), afterload] were set by a servo controller. Intralymphangion pressure (P(L)) was measured using a servo-null micropipette while internal diameter and valve positions were monitored using video methods. The responses to step- and ramp-wise increases in P(out) (at low, constant P(in)) were determined. P(L )and diameter data recorded during single contraction cycles were used to generate pressure-volume (P-V) relationships for the subsequent analysis of lymphangion pump behavior. Ramp-wise P(out) elevation led to progressive vessel constriction, a rise in end-systolic diameter, and an increase in contraction frequency. Step-wise P(out) elevation produced initial vessel distention followed by time-dependent declines in end-systolic and end-diastolic diameters. Significantly, a 30% leftward shift in the end-systolic P-V relationship accompanied an 84% increase in dP/dt after a step increase in P(out), consistent with an increase in contractility. Calculations of stroke work from the P-V loop area revealed that robust pumps produced net positive work to expel fluid throughout the entire afterload range, whereas weaker pumps exhibited progressively more negative work as gradual afterload elevation led to pump failure. We conclude that lymphatic muscle adapts to output pressure elevation with an intrinsic increase in contractility and that this compensatory mechanism facilitates the maintenance of lymph pump output in the face of edemagenic and/or gravitational loads.

Hydrodynamic regulation of lymphatic transport and the impact of aging

To accomplish its normal roles in body fluid regulation/macromolecular homeostasis, immune function, and lipid absorption; the lymphatic system must transport lymph from the interstitial spaces, into and through the lymphatics, through the lymphatic compartment of the nodes, back into the nodal efferent lymphatics and eventually empty into the great veins. The usual net pressure gradients along this path do not normally favor the passive movement of lymph. Thus, lymph transport requires the input of energy to the lymph to propel it along this path. To do this, the lymphatic system uses a series of pumps to generate lymph flow. Thus to regulate lymph transport, both lymphatic pumping and resistance must be controlled. This review focuses on the regulation of the intrinsic lymph pump by hydrodynamic factors and how these regulatory processes are altered with age. Intrinsic lymph pumping is generated via the rapid/phasic contractions of lymphatic muscle, which are modulated by local physical factors (pressure/stretch and flow/shear). Increased lymph pressure/stretch will generally activate the intrinsic lymph pump up to a point, beyond which the lymph pump will begin to fail. The effect of increased lymph flow/shear is somewhat more complex, in that it can either activate or inhibit the intrinsic lymph pump, depending on the pattern and magnitude of the flow. The pattern and strength of the hydrodynamic regulation of the lymph transport is different in various parts of the lymphatic tree under normal conditions, depending upon the local hydrodynamic conditions. In addition, various pathophysiological processes can affect lymph transport. We have begun to evaluate the influence of the aging process on lymphatic transport characteristics in the rat thoracic duct. The pressure/stretch-dependent activation of intrinsic pumping is significantly impaired in aged rat thoracic duct (TD) and the flow/shear-dependent regulatory mechanisms are essentially completely lacking. The loss of shear-dependent modulation of lymphatic transport appears to be related to a loss of normal eNOS expression and a large rise in iNOS expression in these vessels. Therefore, aging of the lymph transport system significantly impairs its ability to transport lymph. We believe this will alter normal fluid balance as well as negatively impact immune function in the aged animals. Further studies are needed to detail the mechanisms that control and alter lymphatic transport during normal and aged conditions.

Noninvasive measurement of edema in partial thickness burn wounds

A lack of noninvasive tools to quantify edema has limited our understanding of burn wound edema pathophysiology in a clinical setting. Near-infrared spectroscopy (NIR) is a new noninvasive tool able to measure water concentration/edema in tissue. The purpose of this study was to determine whether NIR could detect water concentration changes or edema formation in acute partial-thickness burn injuries. Adult burn patients within 72 hours postinjury, thermal etiology, partial-thickness burn depth, and <20% TBSA were included. Burn wounds were stratified into partial-thickness superficial or deep wounds based on histology and wound healing time. NIR devices were used to quantify edema in a burn and respective control sites. The sample population consisted of superficial (n = 12) and deep (n = 5) partial-thickness burn injuries. The patients did not differ with respect to age (40 +/- 15 years), TBSA (5 +/- 4%), and mean time for edema assessment (2 days). Water content increased 15% in burned tissue compared with the respective control regions. There were no differences in water content at the control sites. At 48 hours, deep partial-thickness injuries showed a 23% increase in water content compared with 18% superficial partial-thickness burns. NIR could detect differences in water content or edema formation in partial-thickness burns and unburned healthy regions. NIR holds promise as a noninvasive, portable clinical tool to quantify water content or edema in burn wounds.

Rate-sensitive contractile responses of lymphatic vessels to circumferential stretch

Phasic contractile activity in rat portal vein is more sensitive to the rate of change in length than to absolute length and this response is widely assumed to be a general characteristic of myogenic behaviour for vascular smooth muscle. Previously, we found that rat lymphatic vessels exhibit phasic contractile behaviour similar to that of portal vein. In the present study, we hypothesized that lymphatic muscle would exhibit rate-sensitive contractile responses to stretch. The hypothesis was tested on rat mesenteric lymphatics (90-220 microm, i.d.) using servo-controlled wire- and pressure-myograph systems to enable ramp increases in force or pressure at different rates. Under isometric conditions in wire-myograph preparations, both the amplitude and the frequency of phasic activity were enhanced at more optimal preloads, but superimposed upon this effect were bursts of contractions that occurred only during fast preload ramps. In such cases, the ratio of contraction frequency during the ramp to that at the subsequent plateau (at optimal preload) was > 1. Further, the frequency ratio increased as a function of the preload ramp speed, consistent with a rate-sensitive mechanism. In contrast, the amplitude ratio was < 1 and declined further with higher ramp speeds. Downward preload ramps produced corresponding rate-sensitive inhibition of contraction frequency but not amplitude. Similar findings were obtained in pressurized lymphatics in response to pressure ramps and steps. Our results suggest that lymphatics are sensitive to the rate of change in preload/pressure in a way that is different from portal vein, possibly because the pacemaker for generating electrical activity is rate sensitive but lymphatic muscle is not. The behaviour may be widely present in collecting lymphatic vessels and is probably an important mechanism for rapid adaptation of the lymphatic pump to local vascular occlusion.

Modulation of lymphatic muscle contractility by the neuropeptide substance P

Substance P (SP) is a neuropeptide associated with sensory innervation of lymphoid tissue and a suspected modulator of lymphatic function in inflammation. Only a few studies have examined the effects of SP on lymphatic contraction, and it is not clear to what extent SP acts directly on the lymphatic muscle and/or endothelium or indirectly through changes in intraluminal filling pressure secondary to increases in capillary permeability/filtration. We tested the effects of SP on the spontaneous contractions of rat isolated mesenteric lymphatic vessels under isometric and isobaric conditions, hypothesizing that low concentrations would stimulate lymphatic pumping by enhancing lymphatic muscle contraction in a manner complementary to the effect of increased preload. Under isometric conditions, SP (10 nM) dramatically enhanced lymphatic chronotropy and inotropy. Unlike guinea pig lymphatics, SP actions were not blocked by cyclooxygenase or PLA(2) inhibition. In the absence of SP, ramp increases in isometric preload resulted in x approximately 1.6 increases in contraction amplitude (Amp) and x approximately 1.7 increases in frequency (Freq). SP increased Freq by x approximately 2.4, Amp by x approximately 1.9, and the Amp-Freq product (AFP) by x approximately 3.5. Under isobaric conditions, the pressure elevation from 0.5 to 10 cmH(2)O in the absence of SP decreased Amp by x approximately 0.6 and increased Freq by x approximately 1.8. SP caused a modest increase in Amp, a robust increase in Freq at all pressures, and shifted the AFP-pressure relationship upward and leftward. Therefore, SP has substantial positive inotropic and chronotropic effects on rat lymphatic muscle, improving pump efficiency independent of the effects of preload and broadening of the working range of the lymphatic pump.

Interface pressures produced by two different types of lymphedema therapy devices

BACKGROUND AND PURPOSE

Sequential compression is used to manage lymphedema, but little is known about pressures delivered to the therapeutic targets. This study characterized actual pressures delivered by a traditional compression pump (Lympha Press [LP]) and one using an alternate compression pattern (Flexitouch [FT]).

SUBJECTS

Ten adults who were healthy volunteered to participate in the study.

METHODS

Pressure-time along the forearm was measured using a 256-pressure sensor array during the pressure cycling of each device. Device assessments were separated by at least 48 hours.

RESULTS

Pressure patterns and magnitudes produced by the 2 devices differed considerably. The FT pressure pattern displayed a rapid rise and fall, progressing from the wrist toward the elbow. The LP pressure rose slower and was sustained at a higher level during its inflation cycle. Pressures delivered with the LP were significantly greater than those delivered with the FT.

DISCUSSION AND CONCLUSION

The pressure patterns and magnitudes on treated limbs depend on the device. These differences should be considered before selecting a device for a specific patient.

Postural Effects on Interstitial Fluid Pressure in Humans

BACKGROUND

Direct assessment of the effect of postural changes on interstitial fluid pressure (IFP) in the human skin under physiological conditions is important for the understanding of mechanisms involved in diseases resulting in lower limb edema. Previous techniques to measure IFP had limitations of being invasive, and acute measurements were not possible. Here we describe the effect of postural changes on IFP in the skin of the foot using the minimally invasive servonulling technique.

RESULTS

Measurements were performed in 12 healthy subjects. IFP (means +/- SD) was significantly higher in the sitting (5.1 +/- 2.9 mm Hg) than in the supine position (-0.3 +/- 3.6 mm Hg, p = 0.04) when measured in the sitting position first. The difference between the sitting and the supine position was not significant when measurements were taken in the supine position first [from 1.0 +/- 4.3 (supine) to 3.6 +/- 6.7 mm Hg (sitting), p = 0.46]. Spontaneous low-frequency pressure fluctuations occurred in 58% of the recordings during sitting, which was almost twice as frequent as in the supine position (33%; p = 0.001), while no effects on lymphatic capillary network extension were observed (p = 0.12).

CONCLUSION

Using the servonulling micropressure system, postural effects on IFP can be directly assessed. IFP is higher in the sitting position, but differences are influenced by the time in the upright position.

Transcapillary fluid balance consequences of missing initial lymphatics studied in a mouse model of primary lymphoedema

To investigate the phenotypic consequences of a deranged lymphangiogenesis in relation to tissue fluid accumulation and the possible role of inflammation in the pathogenesis of lymphoedema, we measured determinants of transcapillary fluid filtration and inflammatory mediators in the interstitial fluid in genetically engineered Chy mice, a model for primary congenital lymphoedema (Milroy's disease). Although initial lymphatics were not present in dermis in any of the areas studied (fore paw, hind paw, thigh and back skin) interstitial fluid pressure (P(if)), measured with micropipettes, and tissue fluid volumes were significantly increased only in the areas with visible swelling - the fore and hind paw, whereas interstitial colloid osmotic pressure (COP(if)) was increased in all the skin areas examined. A volume load of 15% of body weight resulted in a more pronounced increase in P(if) as well as a four-fold increase in interstitial fluid volume in Chy relative to wild-type (wt) mice, showing the quantitative importance of lymphatics for fluid homeostasis during acute perturbations. A similar level of proinflammatory markers in interstitial fluid in early established lymphoedema (3-4 months) in Chy and wt suggests that inflammation does not have a major pathogenetic role for the development of lymphoedema, whereas a reduced level of the immunomodulatory cytokine interleukin (IL)-4 may result in a reduced immunological defence ability and thus lead to the increase in inflammatory cytokines IL-2 and IL-6 observed at a later stage (11-13 months). Our data suggest that primary lymphoedema results in a high interstitial fluid protein concentration that does not induce an interstitial inflammatory reaction per se, and furthermore shows the paramount importance of the initial lymphatics in tissue fluid homeostasis, especially during perturbations of transcapillary fluid balance.

Severe lymphatic microangiopathy in Fabry disease

BACKGROUND

Lymphedema has been described in a few cases of Fabry disease. The etiology of lymphedema in Fabry disease is unknown. The aim of the study was to evaluate morphology and function of lymphatic microvessels in this disease.

METHODS AND RESULTS

In five male patients with Fabry disease, the initial lymphatic microvessels of the skin were studied in vivo, using a nearly atraumatic technique of fluorescence microlymphography and measurement of lymph capillary pressure. In addition, five female patients heterozygous for Fabry disease and 12 healthy controls were studied. The maximum spread of the fluorescent macromolecular dye into the network of superficial skin lymphatics was increased in the three male patients presenting with lymphedema (25, 26, and 45 mm, respectively). In the two male patients without swollen legs, the maximum spread of the dye was 3 and 7 mm, respectively, and in the female patients 8.8 mm (range, 4-17 mm), whereas in the healthy controls it reached only 4.3 mm (range, 1-7 mm). Fragmentation of the microlymphatic network was found in all patients, but not in controls. In controls, the diameter of the microvessels varied in a very narrow range (45-75 microm); in patients, the range was 15-150 microm. In patients with lymphedema, microlymphatic hypertension was present.

CONCLUSION

In patients with Fabry disease severe structural and functional changes of the initial lymphatics of the skin are present.

Isoprostane 8-epi-prostaglandin F2 alpha decreases lymph capillary pressure in patients with primary lymphedema

In patients with lymphedema, reduced lymph drainage capacity results in an overloaded superficial microlymphatic network and microlymphatic hypertension. In in vitro experiments, it has been shown that 8-epi-prostaglandin F2 alpha (PGF) induced contractions in human lymphatics. Since lymphatic contractility plays a crucial role in the regulation and generation of lymph transport, we studied the effect of PGF on microlymphatic dynamics by measuring lymph capillary pressure (LCP). Twenty healthy volunteers and 13 patients with primary lymphedema were studied after either PGF or placebo was applied to the skin and occlusively covered for 30 min. Glass micropipettes (7-9 microm) were inserted under microscopic control into initial lymphatics visualized by fluorescence microlymphography and pressure measurements were performed using the servo-nulling technique. The mean LCP in patients with lymphedema was significantly higher (19.8 +/- 12.1 mm Hg) than that in healthy controls (8.4 +/- 4.1 mm Hg) at the placebo-treated site and decreased to normal values after PGF (10.0 +/- 7.7 mm Hg). In healthy volunteers, there was no significant decrease of LCP with PGF compared to placebo. PGF normalizes microlymphatic hypertension in patients with lymphedema by improving lymph transport into deeper channels.

Lymphatic function, lymphangiogenesis, and cancer metastasis

The lymphatic system serves as the primary route for the metastasis of many cancers and the extent of lymph node involvement is the most important indicator of tumor aggressiveness. Despite the apparent importance of the lymphatic vessels for tumor dissemination, it has remained unclear whether activation of lymphatic endothelial cells may affect tumor progression and metastasis and the molecular mechanisms of lymphangiogenesis are just beginning to be elucidated. This overview describes the unique structural and functional characteristics of the lymphatic vessels that render them particularly suitable for invasion by tumor cells and for their efficient transport to lymph nodes. Recent evidence indicates occurrence of tumor lymphangiogenesis and its correlation with metastasis. Molecular regulation of tumor lymphangiogenesis, its significance for tumor metastasis, and implications for cancer therapy are discussed.

Investigation of chronic venous insufficiency: A consensus statement (France, March 5-9, 1997)

This consensus document provides an up-to-date account of the various methods available for the investigation of chronic venous insufficiency of the lower limbs (CVI), with an outline of their history, usefulness, and limitations. CVI is characterized by symptoms or signs produced by venous hypertension as a result of structural or functional abnormalities of veins. The most frequent causes of CVI are primary abnormalities of the venous wall and the valves and secondary changes due to previous venous thrombosis that can lead to reflux, obstruction, or both. Because the history and clinical examination will not always indicate the nature and extent of the underlying abnormality (anatomic extent, pathology, and cause), a number of diagnostic investigations have been developed that can elucidate whether there is calf muscle pump dysfunction and determine the anatomic extent and severity of obstruction or reflux. The difficulty in deciding which investigations to use and how to interpret the results has stimulated the development of this consensus document. The aim of this document was to provide an account of these tests, with an outline of their usefulness and limitations and indications of which patients should be subjected to the tests and when and of what clinical decisions can be made. This document was written primarily for the clinician who would like to learn the latest approaches to the investigation of patients with CVI and the new applications that have emerged from recent research, as well as for the novice who is embarking on venous research. Care has been taken to indicate which methods have entered the clinical arena and which are mainly used for research. The foundation for this consensus document was laid by the faculty at a meeting held under the auspices of the American Venous Forum, the Cardiovascular Disease Educational and Research Trust, the European Society of Vascular Surgery, the International Angiology Scientific Activity Congress Organization, the International Union of Angiology, and the Union Internationale de Phlebologie at the Abbaye des Vaux de Cernay, France, on March 5 to 9, 1997. Subsequent input by co-opted faculty members and revisions in 1998 and 1999 have ensured a document that provides an up-to-date account of the various methods available for the investigation of CVI.

Effect of venous and lymphatic congestion on lymph capillary pressure of the skin in healthy volunteers and patients with lymph edema

The aim of the present study was to assess the influence of venous and lymphatic congestion on lymph capillary pressure (LCP) in the skin of the foot dorsum of healthy volunteers and of patients with lymph edema. LCP was measured at the foot dorsum of 12 patients with lymph edema and 18 healthy volunteers using the servo-nulling technique. Glass micropipettes (7-9 microm) were inserted under microscopic control into lymphatic microvessels visualized by fluorescence microlymphography before and during venous congestion. Venous and lymphatic congestion was attained by cuff compression (50 mm Hg) at the thigh level. Simultaneously, the capillary filtration rate was measured using strain gauge plethysmography. The mean LCP in patients with lymph edema increased significantly (p < 0.05) during congestion (15.7 +/- 8.8 mm Hg) compared to the control value (12.2 +/- 8.9 mm Hg). The corresponding values of LCP in healthy volunteers were 4.3 +/- 2.6 mm Hg during congestion and 2.6 +/- 2.8 mm Hg during control conditions (p < 0.01). The mean increase in LCP in patients with lymph edema was 3.4 +/- 4.1 mm Hg, and 1.7 +/- 2.0 mm Hg in healthy volunteers (NS). The maximum spread of the lymph capillary network in patients increased from 13.9 +/- 6.8 mm before congestion to 18.8 +/- 8.2 mm during thigh compression (p < 0.05). No increase could be observed in healthy subjects. In summary, venous and lymphatic congestion by cuff compression at the thigh level results in a significant increase in LCP in healthy volunteers as well as in patients with lymph edema. The increased spread of the contrast medium in the superficial microlymphatics in lymph edema patients indicates a compensatory mechanism for lymphatic drainage during congestion of the veins and lymph collectors of the leg.

Lymphedema: anatomy, physiology and pathogenesis

The authors review the current understanding of lymphatic anatomy and physiology, and the pathophysiology of lymphedema. The skin lymphatic system consists of the initial lymphatics, which converge into lymphatic precollectors, collectors and lymphatic ducts; these in turn convey the lymph to the regional lymph nodes. Interstitial fluid and particles enter the initial lymphatics through interendothelial openings and by vesicular transport. Lymphatic uptake is enhanced by external compression. Lymphatic transport depends greatly on contraction of lymphangions, which generate the suction force that promotes absorption of interstitial fluid and expels lymph to collecting ducts. In lymphedema, various types of congenital and acquired abnormalities of lymphatic vessels and lymph nodes have been observed. These often lead to lymphatic hypertension, valvular insufficiency and lymphostasis. Accumulation of interstitial and lymphatic fluid within the skin and subcutaneous tissue stimulates fibroblasts, keratinocytes and adipocytes eventuating in the deposition of collagen and glycosaminoglycans within the skin and subcutaneous tissue together with skin hypertrophy and destruction of elastic fibers.

Quantification of the initial lymphatic network in normal human forearm skin using fluorescence microlymphography and stereological methods

Fluorescence microlymphography enables the visualization of the initial lymphatic network in human dermis in vivo. In order to determine which objective, measurable parameters are likely to be of value in future studies, microlymphangiograms were obtained from normal forearm skin of eight men and nine women of a range of ages and analyzed stereologically to calculate: (1) lymphatic length density at a specified radial distance, r, from the site of injection of the fluorescent dye (LDr, cm-1); (2) maximum lymphatic density (LDmax, cm-1); (3) total length of filled lymphatic (LL, cm); (4) maximum radial spread of vessels (mm). There was no significant difference between the right and left arms for peak LDr, LDmax, LL, or spread. Mean values (+/-SD) for the right and left arms combined (n = 24) were 13.34 +/- 7.61 cm-1; 19.31 +/- 8.96 cm-1; 12.04 +/- 10.04 cm; and 7.58 +/- 3.30 mm, respectively. Unexpectedly, three of the four parameters were significantly lower in women compared to men. For women LDmax was 30% lower than for men (P = 0.04), LL was 59% lower (P = 0.032), and spread was 39% lower (P = 0.007). Peak LDr did not differ significantly. Stereological analysis of fluorescent microlymphangiograms enables quantification of the dermal initial lymphatic network and hence the objective study of the influence of gender, age, and disease (including treatment interventions).

Effect of postural changes on human lymphatic capillary pressure of the skin

1. The influence of postural changes on cutaneous lymphatic capillary pressure and venous pressure was measured at the dorsum of the foot in twelve healthy volunteers. Measurements were performed in the supine and sitting positions. 2. Lymphatic skin capillaries were visualized by fluorescence microlymphography with fluorescein isothiocyanate (FITC)-Dextran 150000. Subsequently a lymphatic capillary was punctured with a glass micropipette and pressure was measured using the servo-nulling technique. Lymphatic capillary pressure, venous pressure, heart and respiration rates were recorded simultaneously. 3. Mean lymphatic capillary pressure was significantly higher (P = 0.0096) in the sitting (9.9 +/- 3.0 mmHg) than in the supine (3.9 +/- 4.2 mmHg) position. There was no significant difference (P = 0.09) between lymphatic capillary pressure and venous pressure (6.8 +/- 3.4 mmHg) in the supine position. During sitting mean lymphatic capillary pressure was significantly lower (P = 0.0022) than mean venous pressure (53.3 +/- 4.1 mmHg). The smaller increase in lymphatic capillary pressure may be caused by the discontinuous fluid column in the lymphatic system and enhanced orthostatic contractile activity of lymphatic collectors and precollectors. Spontaneous low frequency pressure fluctuations occurred in 89% of recordings during sitting, which was significantly (P = 0.02) higher than in the supine position (54%). 4. The present results support the suggestion of enhanced intrinsic contractile activity of lymph precollectors and collectors in the dependent position. This mechanism is primarily responsible for the propulsion of lymph from the periphery to the thoracic duct during quiet sitting, when extrinsic pumping by the calf muscles is not active.