Surgical creation of lymphocutaneous fistulas for the management of infants with central lymphatic obstruction.

PURPOSE: Central lymphatic obstructions are associated with anasarca and high mortality. We hypothesized that opening dilated cutaneous lymphatic channels by creating a lymphocutaneous fistula (LCF) would decompress the lymphatic circulation and improve anasarca. METHODS: We reviewed all patients that had at least one LCF created between 9/2019 and 12/2022. LCF efficacy was determined by changes in weight, urine/diuresis, ventilation, and clinical status. RESULTS: We created eleven LCFs in four infants. LCFs initially drained 108 cc/kg/d (IQR68-265 cc/kg/d). Weights significantly decreased after LCF creation (6.9 [IQR6.1-8.1] kg vs. 6.1 [IQR 4.9-7.6] kg, P = 0.042). Ventilatory support decreased significantly in all patients after at least one LCF was created, and 3/4 patients (75%) had significantly lower peak inspiratory pressures (28 [IQR 25-31] cmH2O vs. 22 [IQR 22-24] cmH2O, P = 0.005; 36 [IQR36-38] cmH2O vs. 33 [IQR 33-35] cmH2O, P = 0.002; 36 [IQR 34-47] cmH2O vs. 28 [28-31] cmH2O, P = 0.002). LCFs remained patent for 29d (IQR 16-49d). LCFs contracted over time, and 6/11 (54.5%) were eventually revised. There were no complications. Two patients died from overwhelming disease, one died from unrelated causes, and one remains alive 29 months after their initial LCF. CONCLUSION: LCFs provide safe and effective temporary lymphatic decompression in patients with central lymphatic obstruction. While LCFs are not a cure, they can serve as a bridge to more definitive therapies or spontaneous lymphatic remodeling. LEVEL OF EVIDENCE: IV.

Dynamic contrast-enhanced MR lymphangiography: feasibility of using ferumoxytol in patients with chronic kidney disease.

PURPOSE: To assess the feasibility of direct intra-lymphatic administration of diluted ferumoxytol as a T1-positive contrast agent for dynamic contrast-enhanced MR lymphangiography (DCMRL) imaging of the central lymphatics in children with renal disease. METHODS: In vitro scan of dilute ferumoxytol was initially performed using time-resolved and high-resolution 3D gradient echo (GRE) sequences with short TE values (1 to 1.5 ms). A ferumoxytol concentration of 0.25 to 0.40 mg/mL was found to retain high signal in the T1-weighted sequences. DCMRL was then performed in 4 children with renal disease with the same 3D GRE sequences administrating diluted ferumoxytol via intra-mesenteric (IM), intra-hepatic (IH), and intra-nodal (IN) routes (6 to 9 mL to each site; average total dose of 0.75 mg/kg) by slow hand injection (0.5 to 1.0 mL/min). The signal-to-noise ratio (SNR) of the lymphatics was measured for quantitative evaluation. RESULTS: Ferumoxytol-enhanced DCMRL was technically successful in all patients. Contrast conspicuity within the lymphatics was sufficient without subtraction. The mean SNR was significantly higher than the muscle (50.1 ± 12.2 vs 13.2 ± 2.8; t = 15.9; p < .001). There were no short-term complications attributed to the administration of ferumoxytol in any of the four patients. CONCLUSION: Magnetic resonance lymphangiography using ferumoxytol via IN, IH, and IM access is a new method to directly visualize the central lymphatic system and can be applied safely in patients with renal failure based on our preliminary report of four cases. Ferumoxytol-enhanced DCMRL shows diagnostic image quality by using 3D GRE sequences with short TE values and appropriate dilution of ferumoxytol. KEY POINTS: • MR lymphangiography using ferumoxytol via intra-nodal, intra-hepatic, and intra-mesenteric access is a new method to directly visualize the central lymphatic system from the groin to the venous angle. • FDCMRL can be applied safely in patients with renal failure based on our preliminary report of four cases. • FDCMRL shows diagnostic image quality by using 3D GRE sequences with short TE values and appropriate dilution of the ferumoxytol.

Liver lymphatic anatomy and role in systemic lymphatic disease.

OBJECTIVES: To characterize hepatic to systemic lymphatic connections in patients with systemic lymphatic disease using intra-hepatic lymphangiography and to compare outcomes after lymphatic intervention. METHODS: In 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. RESULTS: During 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. CONCLUSION: We 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.

Dynamic Contrast Magnetic Resonance Lymphangiography Localizes Lymphatic Leak to the Duodenum in Protein-Losing Enteropathy.

OBJECTIVES: Protein-losing enteropathy (PLE) is a disorder of intestinal lymphatic flow resulting in leakage of protein-rich lymph into the gut lumen. Our primary aim was to report the imaging findings of dynamic contrast magnetic resonance lymphangiography (DCMRL) in patients with PLE. Our secondary objective was to use these imaging findings to characterize lymphatic phenotypes. METHODS: Single-center retrospective cohort study of patients with PLE unrelated to single-ventricle circulation who underwent DCMRL. We report imaging findings of intranodal (IN), intrahepatic (IH), and intramesenteric (IM) access points for DCMRL. RESULTS: Nineteen patients 0.3-58 years of age (median 1.2 years) underwent 29 DCMRL studies. Primary intestinal lymphangiectasia (PIL) was the most common referring diagnosis (42%). Other etiologies included constrictive pericarditis, thoracic insufficiency syndrome, and genetic disorders. IN-DCMRL demonstrated a normal central lymphatic system in all patients with an intact thoracic duct and localized duodenal leak in one patient (1/19, 5%). IH-DCMRL detected a duodenal leak in 12 of 17 (71%), and IM-DCMRL detected duodenal leak in 5 of 6 (83%). Independent of etiology, lymphatic leak was only visualized in the duodenum. CONCLUSIONS: In patients with PLE, imaging via DCMRL reveals that leak is localized to the duodenum regardless of etiology. Comprehensive imaging evaluation with three access points can provide detailed information about the site of duodenal leak.

Post-operative Chylothorax in Patients with Repaired Transposition of the Great Arteries.

Patients with dextro-transposition of the great arteries (d-TGA) require surgical repair as neonates. These patients are at risk for post-operative chylothorax. We sought to describe the presentation, imaging, and outcomes after intervention for patients with d-TGA with post-operative chylothorax. A retrospective chart review was performed in patients with repaired d-TGA who were referred from 1/1/2013 to 4/1/2020 for evaluation of chylothorax. Patient history, lymphatic imaging, and interventional data were collected. Impact of intervention on lymphatic drainage was evaluated with a student's t-test. Eight patients met inclusion criteria for this study. Five patients had a history of central venous thrombus leading to thoracic duct outlet occlusion. Five patients underwent intervention, two were managed conservatively, and one was not a candidate for intervention. Chylothorax resolved in six patients. There was a significant difference in output from 7 days prior to first intervention (114 mL/kg/day) compared to 28 days following final intervention (27 mL/kg/day, p = 0.034). There were no procedural complications. Chylothorax in patients with repaired transposition of the great arteries is often amenable to intervention. Early surveillance and management of central venous thrombosis may reduce the burden of lymphatic disease in these patients.

Use of Contrast-Enhanced Ultrasound to Determine Thoracic Duct Patency.

The aim of this study was to determine the feasibility of using contrast-enhanced ultrasound (CEUS) evaluation to determine thoracic duct (TD) outlet patency. Nine patients referred for lymphatic imaging and intervention underwent percutaneous intranodal ultrasound contrast injection and conventional lymphangiography (CL). Eight of 9 patients had a patent TD by CEUS and CL. One patient did not have a patent TD. There was 100% agreement between CEUS and CL. These results suggest that CEUS is an imaging modality that might be as accurate as CL in determining TD patency.

MRI Evaluation of Lymphatic Abnormalities in the Neck and Thorax after Fontan Surgery: Relationship with Outcome.

Background The Fontan operation is performed for surgical palliation of single ventricle physiology. This operation is usually preceded by a superior cavopulmonary connection (SCPC); lymphatic abnormalities after SCPC may be demonstrated at MRI and prior to the Fontan operation. Purpose To determine if the degree of neck and thoracic lymphatic abnormalities at T2-weighted MRI in patients after superior cavopulmonary connection (SCPC) correlated with surgical outcomes from the Fontan procedure. Materials and Methods Patients for whom SCPC was performed for palliation of single ventricle disease who underwent chest MRI between July 2012 and May 2015 at a single institution were retrospectively reviewed. T2-weighted images were scored as lymphatic type 1 (little or no T2 mediastinal and supraclavicular signal) to type 4 (T2 signal into both the mediastinum and the lung parenchyma). Fontan takedown, duration of post-Fontan hospitalization and pleural effusion, postoperative plastic bronchitis, need for transplant, and mortality were tabulated. The relationship between lymphatic type and clinical outcomes was evaluated by using analysis of variance (ANOVA), the Kruskal-Wallis H test, and the Fisher exact test. Results A total of 83 patients (mean age, 7.9 years ± 2.6) were evaluated. Among these 83 patients, 53 (64%) were classified with type 1 or 2 lymphatic abnormalities, 17 (20%) with type 3, and 12 (16%) with type 4. The rate of failure of Fontan completion was higher in patients with type 4 than in type 1 or 2 (54% vs 2%, respectively; P = .004). Need for cardiac transplant (one of 13 [8%]) and death (three of 13 [23%]) occurred only in type 4. Median postoperative length of stay was longer for patients with type 4 than for those with types 1 or 2 (29 days vs 9 days, respectively; P < .01). Conclusion Greater MRI-based severity of lymphatic abnormalities in patients prior to planned Fontan procedure was associated with failure of Fontan completion and longer postoperative stay. © RSNA, 2019 Online supplemental material is available for this article.

Surgical Management of Central Lymphatic Conduction Disorders: A Review.

AIM: Recent advances in lymphatic imaging allow understanding the pathophysiology of lymphatic central conduction disorders with great accuracy. This new imaging data is leading to a wide range of novel surgical interventions. We present here the state-of-the-art imaging technology and current spectrum of surgical procedures available for patients with these conditions. METHOD: Descriptive report of the newest lymphatic imaging technology and surgical procedures and retrospective review of outcome data. RESULTS: There are currently two high-resolution imaging modalities for the central lymphatic system: multi-access dynamic contrast-enhanced MR lymphangiogram (DCMRL) and central lymphangiography (CL). DCMRL is done by accessing percutaneously inguinal and mesenteric lymph nodes and periportal lymphatics vessels. DCMRL provides accurate anatomical and dynamic data on the progression, or lack thereof, of the lymphatic fluid throughout the central lymphatic system. CL is done by placing a catheter percutaneously in the thoracic duct (TD). Pleural effusions are managed by pleurectomy and intraoperative lymphatic glue embolization guided by CL. Anomalies of the TD are managed by TD-to-vein anastomosis and/or ligation of aberrant TD branches. Chylous ascites and organ-specific chylous leaks are managed by intraoperative glue embolization, surgical lymphocutaneous fistulas, and ligation of aberrant peripheral lymphatic channels, among several other procedures. CONCLUSION: The surgical management of lymphatic conduction disorders is a new growing field within pediatric general surgery. Pediatric surgeons should be familiar with the newest imaging modalities of the lymphatic system and with the surgical options available for patients with these complex surgical conditions to provide prompt treatment or referral. LEVEL OF EVIDENCE: V.

Multidisciplinary approach to patients with lymphatic conduction disorders.

Patients with lymphatic disorders are remarkably complex and require a wide variety of medical and surgical services. Establishing a multidisciplinary program improves the efficiency of the patients' hospital experience minimizing the compartmentalization of their care. Offering a clear intake process guarantees that patients will be seen promptly by all the required teams. Additionally, having regular multidisciplinary meetings allows all participating teams to learn from each other and gain experience in the care of a population that is extraordinarily heterogeneous. Additionally, establishing a solid program allows for long-term data collection, research and education.

Critical care management of patients with lymphatic conduction disorders.

Lymphatic dysfunction in critical illness is complex. Primary complex lymphatic anomalies can lead to profound organ dysfunction, particularly respiratory failure and shock. Critical illness, the complications of critical illness, and the procedures and therapies used to treat critical illness, can lead to secondary lymphatic dysfunction. This is most often seen with congenital and acquired cardiovascular disease and respiratory disease. The critical care management of these patients requires an expert multidisciplinary team.

Sequential MRI Evaluation of Lymphatic Abnormalities over the Course of Fontan Completion.

Purpose To evaluate lymphatic abnormalities before and after Fontan completion using noncontrast lymphatic imaging and relate findings with postoperative outcomes. Materials and Methods This study is a retrospective review of noncontrast T2-weighted lymphatic imaging performed at The Children's Hospital of Philadelphia from June 2012 to February 2023 in patients with single ventricle physiology. All individuals with imaging at both pre-Fontan and Fontan stages were eligible. Lymphatic abnormalities were classified into four types based on severity and location of lymphatic vessels. Classifications were compared between images and related to clinical outcomes such as postoperative drainage and hospitalization, lymphatic complications, heart transplant, and death. Results Forty-three patients (median age, 10 years [IQR, 8-11]; 20 [47%] boys, 23 [53%] girls) were included in the study. Lymphatic abnormalities progressed in 19 individuals after Fontan completion (distribution of lymphatic classifications: type 1, 23; type 2, 11; type 3, 6; type 4, 3 vs type 1, 10; type 2, 18; type 3, 10; type 4, 5; P = .04). Compared with individuals showing no progression of lymphatic abnormalities, those progressing to a high-grade lymphatic classification had longer postoperative drainage (median time, 9 days [IQR, 6-14] vs 17 days [IQR, 10-23]; P = .04) and hospitalization (median time, 13 days [IQR, 9-25] vs 26 days [IQR, 18-30]; P = .03) after Fontan completion and were more likely to develop chylothorax (12% [three of 24] vs 75% [six of eight]; P < .01) and/or protein-losing enteropathy (0% [0 of 24] vs 38% [three of eight]; P < .01) during a median follow-up of 8 years (IQR, 5-9). Progression to any type was not associated with an increased risk of adverse events. Conclusion The study demonstrated that lymphatic structural abnormalities may progress in select individuals with single ventricle physiology after Fontan completion, and progression of abnormalities to a high-grade classification was associated with worse postoperative outcomes. Keywords: Congenital Heart Disease, Glenn, Fontan, Lymphatic Imaging, Cardiovascular MRI Supplemental material is available for this article. Published under a CC BY 4.0 license.

Lymphatic disorders caused by mosaic, activating KRAS variants respond to MEK inhibition.

Central conducting lymphatic anomaly (CCLA) due to congenital maldevelopment of the lymphatics can result in debilitating and life-threatening disease with limited treatment options. We identified 4 individuals with CCLA, lymphedema, and microcystic lymphatic malformation due to pathogenic, mosaic variants in KRAS. To determine the functional impact of these variants and identify a targeted therapy for these individuals, we used primary human dermal lymphatic endothelial cells (HDLECs) and zebrafish larvae to model the lymphatic dysplasia. Expression of the p.Gly12Asp and p.Gly13Asp variants in HDLECs in a 2­dimensional (2D) model and 3D organoid model led to increased ERK phosphorylation, demonstrating these variants activate the RAS/MAPK pathway. Expression of activating KRAS variants in the venous and lymphatic endothelium in zebrafish resulted in lymphatic dysplasia and edema similar to the individuals in the study. Treatment with MEK inhibition significantly reduced the phenotypes in both the organoid and the zebrafish model systems. In conclusion, we present the molecular characterization of the observed lymphatic anomalies due to pathogenic, somatic, activating KRAS variants in humans. Our preclinical studies suggest that MEK inhibition should be studied in future clinical trials for CCLA due to activating KRAS pathogenic variants.

Genomic profiling informs diagnoses and treatment in vascular anomalies.

Vascular anomalies are malformations or tumors of the blood or lymphatic vasculature and can be life-threatening. Although molecularly targeted therapies can be life-saving, identification of the molecular etiology is often impeded by lack of accessibility to affected tissue samples, mosaicism or insufficient sequencing depth. In a cohort of 356 participants with vascular anomalies, including 104 with primary complex lymphatic anomalies (pCLAs), DNA from CD31+ cells isolated from lymphatic fluid or cell-free DNA from lymphatic fluid or plasma underwent ultra-deep sequencing thereby uncovering pathogenic somatic variants down to a variant allele fraction of 0.15%. A molecular diagnosis, including previously undescribed genetic causes, was obtained in 41% of participants with pCLAs and 72% of participants with other vascular malformations, leading to a new medical therapy for 63% (43/69) of participants and resulting in improvement in 63% (35/55) of participants on therapy. Taken together, these data support the development of liquid biopsy-based diagnostic techniques to identify previously undescribed genotype-phenotype associations and guide medical therapy in individuals with vascular anomalies.

Genetics etiologies and genotype phenotype correlations in a cohort of individuals with central conducting lymphatic anomaly.

Central conducting lymphatic anomaly (CCLA) is a heterogenous disorder caused by disruption of central lymphatic flow that may result in dilation or leakage of central lymphatic channels. There is also a paucity of known genetic diagnoses associated with CCLA. We hypothesized that specific genetic syndromes would have distinct lymphatic patterns and this would allow us to more precisely define CCLA. As a first step toward "precision lymphology", we defined the genetic conditions associated with CCLA by performing a retrospective cohort study. Individuals receiving care through the Jill and Mark Fishman Center for Lymphatic Disorders at the Children's Hospital of Philadelphia between 2016 and 2019 were included if they had a lymphangiogram and clinical genetic testing performed and consented to a clinical registry. In our cohort of 115 participants, 26% received a molecular diagnosis from standard genetic evaluation. The most common genetic etiologies were germline and mosaic RASopathies, chromosomal abnormalities including Trisomy 21 and 22q11.2 deletion syndrome, and PIEZO1-related lymphatic dysplasia. Next, we analyzed the dynamic contrast magnetic resonance lymphangiograms and found that individuals with germline and mosaic RASopathies, mosaic KRASopathies, PIEZO1-related lymphatic dysplasia, and Trisomy 21 had distinct central lymphatic flow phenotypes. Our research expands the genetic conditions associated with CCLA and genotype-lymphatic phenotype correlations. Future descriptions of CCLA should include both genotype (if known) and phenotype to provide more information about disease (gene-CCLA). This should be considered for updated classifications of CCLA by the International Society of Vascular Anomalies.

Occlusion Pressure of the Thoracic Duct in Fontan Patients With Lymphatic Failure: Does Dilatation Challenge Contractility?

BACKGROUND: The Fontan circulation challenges the lymphatic system. Increasing production of lymphatic fluid and impeding lymphatic return, increased venous pressure may cause lymphatic dilatation and decrease lymphatic contractility. In-vitro studies have reported a lymphatic diameter-tension curve, with increasing passive stretch affecting the intrinsic contractile properties of each thoracic duct segment. We aimed to describe thoracic duct occlusion pressure and asses if thoracic duct dilation impairs contractility in individuals with a Fontan circulation and lymphatic failure. METHODS: Central venous pressure and thoracic duct measurements were retrospectively collected from 31 individuals with a Fontan circulation. Thoracic duct occlusion pressure was assessed during a period of external manual compression and used as an indicator of lymphatic vessel contractility. Measurements of pressure were correlated with measurements of the thoracic duct diameter in images obtained by dynamic contrast-enhanced MR lymphangiography. RESULTS: The average central venous pressure and average pressure of the thoracic duct were 17 mm Hg. During manual occlusion, the thoracic duct pressure significantly increased to 32 mm Hg. The average thoracic duct diameter was 3.3 mm. Thoracic duct diameter correlated closely with the central venous pressure. The rise in pressure following manual occlusion showed an inverse correlation with the diameter of the thoracic duct. CONCLUSION: Higher central venous pressures are associated with increasing diameters of the thoracic duct. When challenged by manual occlusion, dilated thoracic ducts display a decreased ability to increase pressure. Dilatation and a resulting decreased contractility may partly explain the challenged lymphatic system in individuals with a Fontan circulation.

Intrahepatic Dynamic Contrast-Enhanced Magnetic Resonance Lymphangiography: Potential Imaging Signature for Protein-Losing Enteropathy in Congenital Heart Disease.

Background Protein-losing enteropathy (PLE) is a significant cause of morbidity and mortality in congenital heart disease patients with single ventricle physiology. Intrahepatic dynamic contrast-enhanced magnetic resonance lymphangiography (IH-DCMRL) is a novel diagnostic technique that may be useful in characterizing pathologic abdominal lymphatic flow in the congenital heart disease population and in diagnosing PLE. The objective of this study was to characterize differences in IH-DCMRL findings in patients with single ventricle congenital heart disease with and without PLE. Methods and Results This was a single-center retrospective study of IH-DCMRL findings and clinical data in 41 consecutive patients, 20 with PLE and 21 without PLE, with single ventricle physiology referred for lymphatic evaluation. There were 3 distinct duodenal imaging patterns by IH-DCMRL: (1) enhancement of the duodenal wall with leakage into the lumen, (2) enhancement of the duodenal wall without leakage into the lumen, and (3) no duodenal involvement. Patients with PLE were more likely to have duodenal involvement on IH-DCMRL than patients without PLE (P<0.001). Conclusions IH-DCMRL findings of lymphatic enhancement of the duodenal wall and leakage of lymph into the duodenal lumen are associated with PLE. IH-DCMRL is a useful new modality for characterizing pathologic abdominal lymphatic flow in PLE and might be useful as a risk-assessment tool for PLE in at-risk patients.

Neonatal lymphatic flow disorders: impact of lymphatic imaging and interventions on outcomes.

Neonatal chylothorax (NCTx) and central lymphatic flow disorder (CLFD) are historically challenging neonatal disorders with high morbidity and mortality. METHODS: We conducted a retrospective study of 35 neonates with pulmonary lymphatic abnormalities at our institution who underwent lymphatic evaluation between December 2015 and September 2018. Patients with only pulmonary lymphatic perfusion syndrome were classified as NCTx and those with multiple flow abnormalities were classified as CLFD. Demographics, clinical characteristics, and outcomes were compared using t-tests/Wilcoxon rank sum tests and Fisher's exact tests. RESULTS: All 35 patients had intranodal MR lymphangiography and 14 (40%) also had conventional fluoroscopic lymphangiography. Fifteen (42.8%) patients were diagnosed with NCTx and 20 (57.1%) were diagnosed with CLFD. Thirty-four (97.1%) patients had pleural effusions. None of the NCTx group had ascites, anasarca, or dermal backflow compared to 17 (85%) (p < 0.001), 8 (42.1%) (p: 0.004), and 20 (100%) (p < 0.001) of the CLFD group, respectively. In the NCTx group, 11 (73.3%) had ethiodized oil embolization and 4 (26.7%) received conservative therapy. Ten (50%) of the CLFD patients had an intervention; of those, two (10%) had ethiodized oil-only embolization. Eight had non-ethiodized oil embolizations (two (25%) had embolization with glue, three (37.5%) underwent surgical lymphovenous anastomosis, two (25%) underwent thoracic duct (TD) externalization, and one (12.5%) had a non-TD lymphatic channel drain placed). Complete resolution of pleural effusions was achieved in all 15 NCTx patients, whereas 9 (45%) of 20 CLFD patients had resolution of chylothorax (p: 0.001). CONCLUSIONS: Establishing a diagnosis of NCTx or CLFD is paramount in selecting treatment options and providing prognostic information. Development of lymphatic interventions represents a paradigm shift in our understanding of neonatal lymphatic flow disorders and may be associated with improved survival.

Severe Lymphatic Disorder Resolved With MEK Inhibition in a Patient With Noonan Syndrome and SOS1 Mutation.

Noonan syndrome is a multiorgan system disorder mediated by genetic defects along the RASknown as RASopathies. It is the second most common syndromic cause of congenital heart disease and, in ∼20% of the cases, is associated with severe lymphatic disorders, including chylothorax and protein-losing enteropathy. Recently, we reported on the use of mitogen-activated protein kinase inhibition in a patient with an ARAF mutation and severe lymphatic disorder leading to an abrupt improvement in symptoms and complete remodeling of the central lymphatic system. Here, we present a patient with Noonan syndrome and severe lymphatic abnormality, leading to transfusion-dependent upper gastrointestinal bleeding and protein-losing enteropathy. The patient stopped responding to medical therapy and underwent several lymphatic interventional procedures, which led only to a temporary improvement in symptoms. Because of a lack of other treatment options, an expanded access approval was obtained, and the patient initiated treatment by mitogen-activated protein kinase inhibition using trametinib. This led to resolution of her symptoms, with complete normalization of her electrolyte levels, hemoglobin, and albumin within 3 months of starting the drug. Similar to the previously reported case, she also had complete and generalized remodeling of her lymphatic system. In patients with RAS pathway defects complicated by a severe lymphatic disorder, inhibition of the RAS-MAPK pathway should be considered as a possible treatment option in patients who failed conventional treatment and might be a first-line treatment in the future.

Thoracic duct-to-vein anastomosis for the management of thoracic duct outflow obstruction in newborns and infants: a CASE series.

BACKGROUND: Thoracic duct (TD) outflow obstruction causes high morbidity and mortality in newborns. It can be congenital/idiopathic or acquired (secondary to central venous thrombosis or injury during cardiothoracic surgery). Re-routing the TD to the venous system by microsurgical techniques to restore lymphatic flow is a potential surgical solution. We present a series of newborns and infants who underwent thoracic duct-to-vein anastomosis (TDVA) to restore TD outflow. MATERIALS AND METHODS: A retrospective review of all TDVA September 2015-March 2019 was performed. All patients underwent extensive pre-operative imaging evaluation by dynamic MRI and fluoroscopic lymphangiography. The TDVAs were done under high-power microscopy. RESULTS: Eight patients underwent TDVA. Age at surgery was 1 to 9 months. Four patients had a history of cardiac surgery (one with complete thrombosis of the central venous system), one patient had a history of ECMO and thrombosis of the SVC, and three patients had a history of fetal hydrothorax and non-immune hydrops. Six patients had a successful TDVA with restoration of the lymphatic flow through the TD and clinical improvement. Two patients had a technically adequate TDVA but without improvement of the flow due to persistently high central venous pressure. Five patients remain alive, two patients died from complications of the lymphatic disorder, and one patient died from an unrelated cause. CONCLUSIONS: Patients with congenital or acquired TD outlet obstruction for whom no improvement is achieved by non-surgical interventions may benefit from TDVA. A thorough understanding of the anatomy and physiology of each patient is critical for the success of the operation. LEVEL OF EVIDENCE: Level IV.