Lymphatic Vessel Thrombosis in a Patient with Secondary Lymphedema

Usefulness of 33 MHz Linear Probe in Lymphatic Ultrasound for Lymphedema Patients

Background: Lymphatic ultrasound has recently been reported useful in the treatment of lymphedema. However, no conclusions have been reached regarding the best probe for lymphatic ultrasound. Methods: This was a retrospective study. Fifteen limbs of 13 patients with lymphedema in whom we could not find dilated lymphatic vessels on lymphatic ultrasound with an 18 MHz probe but later could find them with 33 MHz probe were included. All patients were women, and the mean age was 59.5 years. We performed lymphatic ultrasound in four areas per limb by applying an index of D-CUPS, as we previously reported. We measured the depth and diameter of the lumen of the lymphatic vessels. We also diagnosed the degree of lymphatic degeneration based on the normal, ectasis, contraction, and sclerosis type (NECST) classification. Results: We found lymphatic vessels in 22/24 (91.7%) areas in the upper limbs and 26/36 (72.2%) areas in the lower limbs. The mean depth and diameter of the lymphatic vessels were 5.2 ± 0.28 mm and 0.33 ± 0.029 mm, respectively. Based on the NECST classification, 68.2% of the upper limbs and 56.0% of the lower limbs were of the ectasis type. We found functional lymphatic vessels in 6/6 (100%) of the upper limbs and 5/7 (71.4%) of the lower limbs, which indicated lymphaticovenous anastomosis (LVA) in these 11 patients. Conclusion: Using 33 MHz probe, we could detect functional lymphatic vessels in most patients. Even if lymphatic vessels were not found with the 18 MHz probe, LVA could be performed using a higher frequency probe.

Lymphatic coagulation and neutrophil extracellular traps in lung-draining lymph nodes of COVID-19 decedents

Clinical manifestations of severe COVID-19 include coagulopathies that are exacerbated by the formation of neutrophil extracellular traps (NETs). Here, we report that pulmonary lymphatic vessels, which traffic neutrophils and other immune cells to the lung-draining lymph node (LDLN), can also be blocked by fibrin clots in severe COVID-19. Immunostained tissue sections from COVID-19 decedents revealed widespread lymphatic clotting not only in the lung but also in the LDLN, where the extent of clotting correlated with the presence of abnormal, regressed, or missing germinal centers (GCs). It strongly correlated with the presence of intralymphatic NETs. In mice, tumor necrosis factor α induced intralymphatic fibrin clots; this could be inhibited by DNase I, which degrades NETs. In vitro, TNF-α induced lymphatic endothelial cell upregulation of ICAM-1 and CXCL8, among other neutrophil-recruiting factors, as well as thrombomodulin downregulation; in decedents, lymphatic clotting in LDLNs. In a separate cohort of hospitalized patients, serum levels of Myeloperoxidase-DNA (MPO-DNA, a NET marker) inversely correlated with antiviral antibody titers, but D-dimer levels, indicative of blood thrombosis, did not correlate with either. Patients with high MPO-DNA but low D-dimer levels generated poor antiviral antibody titers. This study introduces lymphatic coagulation in lungs and LDLNs as a clinical manifestation of severe COVID-19 and suggests the involvement of NETosis of lymphatic-trafficking neutrophils. It further suggests that lymphatic clotting may correlate with impaired formation or maintenance of GCs necessary for robust antiviral antibody responses, although further studies are needed to determine whether and how lymphatic coagulation affects adaptive immune responses.

Lymphatic refill in ultrasound and lymphatic washout after lymphaticovenous anastomosis

BACKGROUND

Lymphaticovenous anastomosis (LVA) drains lymph accumulated in the lymphatic vessels into the veins (lymphatic washout). A method to identify the ideal lymphatic vessels to achieve washout has not been established. This study examined the relationship between lymphatic washout, lymphatic ultrasonographic findings, and surgical outcomes.

METHODS

We reviewed consecutive patients who underwent LVA for lower limb lymphedema between September 2020 and March 2021. Patients who lacked data were excluded. Preoperative ultrasonography was performed to measure the lymphatic diameter. After the probe was pressed against the skin and released, the reaction of the lymphatic vessels was classified as either refilled, crushed, undecidable, or solid. Intraoperatively, whether lymphatic washout was observed or not, was recorded and compared to preoperative findings using the chi-square test. In 54 limbs from 32 patients, the total number of LVA, number of anastomoses with washout, number of refills detected by ultrasound, and severity of lymphedema were compared with the surgical result (postoperative limb volume change) by multiple regression analysis (49 limbs whose pre-or postoperative circumference data were lacking or who underwent intensive compression therapy postoperatively were excluded).

RESULTS

Sixty-five patients were reviewed. After excluding six patients with missing data, 59 patients (103 limbs) were included. The median patient age was 63 years (interquartile range, 51-76 years). We performed LVA at 217 sites (mean, 2.1 anastomoses per limb). "Refilled" lymphatics were observed at 156 sites (71.6%) and significantly thicker than those classified as "undecidable" (p = .020 in the lower leg and p < .001 in the thigh). In the thigh, "refilled" lymphatics had a higher rate of a washout than those classified as "undecidable." In Pearson's correlation coefficient for the surgical result, as the number of washout positive LVA increased, the limb volume tended to decrease postoperatively (correlation coefficient: -0.25). However, multiple regression analysis did not identify any factors that significantly affected the surgical outcomes.

CONCLUSION

"Refilled" lymphatic vessels had a higher rate of intraoperative lymphatic washout after anastomosis.

The Role of Platelet-Derived Extracellular Vesicles in Immune-Mediated Thrombosis

Platelet-derived extracellular vesicles (PEVs) play important roles in hemostasis and thrombosis. There are three major types of PEVs described based on their size and characteristics, but newer types may continue to emerge owing to the ongoing improvement in the methodologies and terms used to define various types of EVs. As the literature on EVs is growing, there are continuing attempts to standardize protocols for EV isolation and reach consensus in the field. This review provides information on mechanisms of PEV production, characteristics, cellular interaction, and their pathological role, especially in autoimmune and infectious diseases. We also highlight the mechanisms through which PEVs can activate parent cells in a feedback loop.

The accuracy of lymphatic ultrasound in measuring the lymphatic vessel size in lower limb lymphedema patients

BACKGROUND

Lymphatic ultrasound is a newly developed method to observe the lymphatic vessels. In this study, we compared the diameter of lymphatic vessels observed on preoperative ultrasound with the actual lymphatic diameter (LD) of lymphatic vessels observed intraoperatively.

METHODS

The study included 32 lower limbs in 17 patients with lower limb lymphedema. Lymphatic ultrasound was performed using a commonly used ultrasound device, Noblus ultrasound system, with an 18 MHz linear probe on preoperative day 1. We tracked the lymphatic vessels along the great saphenous vein, at the lateral calf, and at the lateral thigh, based on the lymphosome principle. We measured the cross-sectional height (CSH) and the cross-sectional width (CSW) of lymphatic vessels using ultrasound at the incision sites. Intraoperatively, we measured the diameter of the lymphatic vessel. Based on lymphatic degeneration, lymphatic vessels were categorized into four types using the normal-, ectasis-, contraction-, and sclerosis-type (NECST) classification.

RESULTS

We evaluated 68 lymphatic vessels. The mean CSH, CSW, and LD were 0.65 ± 0.35 mm, 1.3 ± 0.41 mm, and 0.79 ± 0.35 mm, respectively. The correlation coefficient between the CSH and the LD was 0.36 and that between the CSW and LD was 0.24. A significant difference was observed in CSH between the ectasis and contraction types (p = 0.0025).

CONCLUSIONS

We can somehow predict the size of the lymphatic vessels with CSH in the lymphatic ultrasound, whereas CSW is not reliable.

Coagulation in Lymphatic System

The lymphatic system maintains homeostasis of the internal environment between the cells in tissues and the blood circulation. The coagulation state of lymph is determined by conditions of coagulation factors and lymphatic vessels. Internal obliteration, external compression or abnormally increased lymphatic pressure may predispose to localized lymphatic coagulation. In physiological conditions, an imbalance of antithrombin and thrombokinase reduces lymphatic thrombosis. However, the release of factor X by lymphatic endothelium injury may trigger coagulation casacade, causing blockage of lymphatic vessels and lymphedema. Heterogeneity of lymphatic vessels in various tissues may lead to distinct levels and patterns of coagulation in specific lymphatic vessels. The quantitative and qualitative measurement of clotting characteristic reveals longer time for clotting to occur in the lymph than in the blood. Cancer, infections, amyloidosis and lymph node dissection may trigger thrombosis in the lymphatic vessels. In contrast to venous or arterial thrombosis, lymphatic thrombosis has rarely been reported, and its actual prevalence is likely underestimated. In this review, we summarize the mechanisms of coagulation in lymphatic system, and discuss the lymphatic thrombosis-related diseases.

Diagnosis of Lymphatic Dysfunction by Evaluation of Lymphatic Degeneration with Lymphatic Ultrasound

Background: The standard examination for diagnosing lymphedema is lymphoscintigraphy, which has a disadvantage in versatility and radiation exposure. We have reported the usefulness of echography in observing the lymphatic degeneration. The purpose of this study was to investigate the usefulness of lymphatic ultrasound in diagnosing lymphedema. Methods and Results: The study included 14 patients (28 lower limbs) who underwent lymphaticovenous anastomosis for lower limb lymphedema. Preoperative echography with a common 18-MHz linear probe was used to detect lymphatic vessels. We evaluated abnormal expansion or sclerosis of lymphatic vessels in the medial legs, which indicated the presence of lymphedema. We proposed the method "D-CUPS" on how to detect and observe the lymphatic vessels. We then performed indocyanine green (ICG) lymphography to diagnose lymphedema. The results of examination were compared. Stage 1 lymphedema was diagnosed in 9 limbs, Stage 2a in 7, Stage 2b in 8, and Stage 3 in 4. Lymphatic vessel detection was possible in all 28 medial thighs and in 27 medial lower legs. The sensitivity and specificity for diagnosis of lymphedema based on echography of the medial leg were 95.0% and 100.0%, respectively. The accuracy rate was 94.6%. We could detect lymphatic vessels with echography in 39 of 54 areas that failed detection using lymphoscintigraphy or ICG lymphography (72.2%). Conclusion: The location and degeneration of lymphatic vessels in lymphedematous limbs can be evaluated with a commonly used ultrasound device. Although exclusion of comorbidities is still necessary, lymphatic ultrasound has potential for use in diagnosis of lymphedema or lymphatic dysfunction.

Change of the Lymphatic Diameter in Different Body Positions

Background: Until now, lymphatic ultrasound was performed with the patients in the prone position. The aim of this study was to evaluate the change in the lymphatic diameter in different body positions. Methods: We performed a retrospective study. We performed indocyanine green (ICG) lymphography and lymphatic ultrasound as a pre-operative examination for lymphaticovenous anastomosis (LVA). ICG was injected at three lymphosomes per limb (the saphenous lymphatics, lateral thigh lymphatics, and lateral calf lymphatics). For the lymphatic ultrasound, a commonly used ultrasound device with an 18 MHz linear probe was employed. We measured the lymphatic diameter in the designed LVA sites in prone, sitting, and upright position. Results: We investigated 61 limbs of 31 female patients with lower limb lymphedema. The mean age was 62.0 (range: 42-86) years. We measured the lymphatic diameter at 78 sites in the thigh and 76 sites in the lower leg. In the thigh, the mean lymphatic diameters in the supine and upright positions were 0.43 ± 0.02 mm and 0.40 ± 0.02 mm, respectively, with no significant difference (p = 0.10). In the lower leg, the mean lymphatic diameters in the supine, sitting, and upright positions were 0.68 ± 0.04 mm, 0.63 ± 0.04 mm, and 0.63 ± 0.04, respectively. A significant decrease was noted between the supine and sitting positions (p = 0.02). Conclusions: The lymphatic diameter in the lymphedematous lower limbs tended to decrease when the patients changed their body position from supine to the sitting or upright positions.