Anatomic and Functional Evaluation of Central Lymphatics With Noninvasive Magnetic Resonance Lymphangiography

Comparison of the Pharmacokinetics of Gadolinium-Based and Iron Oxide-Based Contrast Agents inside the Lymphatic Structure using Magnetic Resonance Lymphangiography

PURPOSE

Gadolinium (Gd)-based contrast agents are primarily used for contrast-enhanced magnetic resonance lymphangiography (MRL). However, overcoming venous contamination issues remains challenging. This study aims to assess the MRL efficacy of the newly developed iron-based contrast agent (INV-001) that is specially designed to mitigate venous contamination issues. The study further explores the optimal dosage, including both injection volume and concentration, required to achieve successful visualization of the popliteal lymph nodes and surrounding lymphatic vessels.

PROCEDURES

All animals utilized in this study were male Sprague-Dawley (SD) rats weighing between 250 and 300 g. The contrast agents prepared were injected intradermally in the fourth phalanx of both hind limbs using a 30-gauge syringe in SD rats. MRL was performed every 16 min on a coronal 3D time-of-flight sequence with saturation bands using a 9.4-T animal machine.

RESULTS

Contrary to Gd-DOTA, which exhibited venous contamination in most animals irrespective of injection dosages and conditions, INV-001 showed no venous contamination. For Gd-DOTA, the popliteal lymph nodes and lymphatic vessels reached peak enhancement 16 min after injection from the injection site and then rapidly washed out. However, with INV-001, they reached peak enhancement between 16 and 32 min after injection, with prolonged visualization of the popliteal lymph node and lymphatic vessels. INV-001 at 0.45 μmol (15 mM, 30 μL) and 0.75 μmol (15 mM, 50 μL) achieved high scores for qualitative image analysis, providing good visualization of the popliteal lymph nodes and lymphatic vessels without issues of venous contamination, interstitial space enhancement, or lymph node enlargement.

CONCLUSION

In MRL, INV-001, a novel T1 contrast agent based on iron, enables prolonged enhancement of popliteal lymph nodes and lymphatic vessels without venous contamination.

Chylothorax: pathophysiology, diagnosis, and management-a comprehensive review

Chylothorax is a rare condition characterized by the accumulation of chyle in the pleural space. While it accounts for a small percentage of pleural effusions, chylothorax can lead to significant morbidity and mortality. This article provides a comprehensive overview of chylothorax, covering its relevant anatomy, aetiology, pathophysiology, clinical features, diagnosis, and management. Injury or disruption to the thoracic duct (which is responsible for chyle transport) leads to the development of chylothorax. This may result from trauma, such as iatrogenic injury during surgery, or non-traumatic causes, including malignancy, lymphatic disorders, and heart failure. Recognition of the underlying cause is essential to tailor management. Clinical presentation varies, with symptoms linked to rate of chyle accumulation and the causative condition. Diagnosis relies on pleural fluid analysis, with demonstration of elevated triglyceride levels (>110 mg/dL) and reduced cholesterol levels (<200 mg/dL) being the key diagnostic criteria employed in clinical practice. Various imaging modalities, including computed tomography (CT) scans and lymphatic-specific investigations, may be utilised to aid identification of the site of chyle leak, as well as determine the likely underlying cause. Chylothorax management is multifaceted, with conservative approaches such as dietary modification and pharmacological interventions often initiated as first-line treatment. Drainage of chylous effusion may be necessary for symptom relief. When conservative methods fail, interventional procedures like thoracic duct ligation or embolization can be considered. Due to the diverse aetiological factors and patient characteristics associated with chylothorax, individualized management strategies are recommended. Nonetheless, management of chylothorax is an evolving field with a paucity of high-quality evidence or standardized guidelines, highlighting the importance of ongoing research and a multidisciplinary approach to optimize individual patient care.

Imaging Findings of Thoracic Lymphatic Abnormalities

The lymphatic system plays an important role in balancing fluid compartments in the body. It is disrupted by various disease processes in the thorax, including injury to the thoracic lymphatic duct after surgery, as well as malignancy and heart failure. Because of the small size of lymphatic vessels, imaging of the lymphatics is relatively difficult, and effective imaging methods are still being optimized and developed. The standard of reference for lymphatic imaging has been conventional lymphangiography for several decades. Other modalities such as CT, noncontrast or contrast-enhanced MRI, and lymphoscintigraphy can also demonstrate lymphatic abnormalities and help in treatment planning. Imaging findings associated with lymphatic abnormalities can be seen in the pulmonary parenchyma, pleural space, and mediastinum. In the pulmonary parenchyma, common findings include interlobular septal thickening as well as reversal of lymphatic flow with intravasation of contrast material into pulmonary lymphatics. In the pleural space, findings include chylous pleural effusion and occasionally nonchylous pleural effusion. In the mediastinum, thoracic duct leak, plexiform thoracic duct, lymphatic malformations, and lymphangiectasis may occur. Management of chylothorax includes conservative or medical treatment, surgery, and interventional radiology procedures. The authors discuss thoracic lymphatic anatomy, imaging manifestations of lymphatic abnormalities in the various anatomic compartments, and interventional radiology treatment of chylothorax. Radiologists should be familiar with these imaging findings for diagnosis and to help guide appropriate management. ^©RSNA, 2022.

The bright future of nanotechnology in lymphatic system imaging and imaging-guided surgery

Lymphatic system is identified the second vascular system after the blood circulation in mammalian species, however the research on lymphatic system has long been hampered by the lack of comprehensive imaging modality. Nanomaterials have shown the potential to enhance the quality of lymphatic imaging due to the unparalleled advantages such as the specific passive targeting and efficient co-delivery of cocktail to peripheral lymphatic system, ease molecular engineering for precise active targeting and prolonged retention in the lymphatic system of interest. Multimodal lymphatic imaging based on nanotechnology provides a complementary means to understand the kinetics of lymphoid tissues and quantify its function. In this review, we introduce the established approaches of lymphatic imaging used in clinic and summarize their strengths and weaknesses, and list the critical influence factors on lymphatic imaging. Meanwhile, the recent developments in the field of pre-clinical lymphatic imaging are discussed to shed new lights on the design of new imaging agents, the improvement of delivery methods and imaging-guided surgery strategies.

Transcatheter Dynamic Contrast-Enhanced MR Lymphangiography for Nontraumatic Lymphatic Disorders: Technical Feasibility and Imaging Findings

This study aimed to evaluate the feasibility and added value of transcatheter dynamic contrast-enhanced magnetic resonance (MR) lymphangiography for nontraumatic lymphatic disorders. Five patients (2 males and 3 females; median age, 16.0 years; range, 3-74 years) who underwent both intranodal and transcatheter dynamic contrast-enhanced MR lymphangiography for suspected nontraumatic lymphatic leakages from June 2017 to January 2020 were included in this retrospective study. The imaging findings of both dynamic contrast-enhanced MR lymphangiography techniques were assessed for the presence of chylolymphatic reflux or direct sign of leakage. Intranodal dynamic contrast-enhanced MR lymphangiography demonstrated chylolymphatic reflux into the thoracic area in 2 patients (40%) but no direct evidence of leakage in any of the 5 patients. Transcatheter dynamic contrast-enhanced MR lymphangiography revealed chylolymphatic reflux and extravasation of the contrast agent in all 5 patients (100%). In conclusion, transcatheter dynamic contrast-enhanced MR lymphangiography may reveal additional signs of reflux and extravasation even when the findings of intranodal dynamic contrast-enhanced MR lymphangiography are negative.

Pragmatic role of noncontrast magnetic resonance lymphangiography in postoperative chylothorax or cervical chylous leakage as a diagnostic and preprocedural planning tool

OBJECTIVES

To define the roles of noncontrast magnetic resonance lymphangiography (MRL) in the management of postoperative chylothorax or cervical chylous leakage.

METHODS

A total of 50 consecutive patients underwent noncontrast MRL, intranodal lymphangiography, and thoracic duct embolization between May 2016 and April 2020. Their mean age was 62.6 years ± 10.3 (SD) years, and 35 of the participants were men. Conventional lymphangiographic images were sufficient in quality as a reference for the evaluation of diagnostic accuracy of leakage and location in 35 patients (70%) and for evaluation of anatomic details of the thoracic duct and jugulovenous junction in 34 patients (68%).

RESULTS

MRL showed that the sensitivity, specificity, and positive and negative predictive values for leakage detection were 100%, 97.1%, 100%, and 100%, respectively, and the concordance rate was 97.14% (95% confidence interval [CI], 85.08-99.93%; p < .001). Leakage location was concordant between MRL and conventional lymphangiography in 27 patients (77.1%, 27/35). Regarding anatomical details of the thoracic duct, variation of the thoracic duct was missed in 11.7% of patients (4/34). The jugulovenous junction was observed in 91.1% (31/34), and its opening into the central vein was depicted in 76.4% (26/34). The concordance rate was between 76.47 and 91.18.

CONCLUSIONS

Noncontrast MRL has a high sensitivity for the detection of postoperative thoracic and cervical chylous leakage but is suboptimal for the localization of the leak and depiction of anatomical details of the thoracic duct. This method is worthy of consideration as either a decision-making or planning tool for subsequent interventions.

KEY POINTS

• Noncontrast MRL provides limited resolution images of CLS but has a high sensitivity for the detection of postoperative chylous leakage in the thoracic and neck regions. • Noncontrast MRL is suboptimal for depicting anatomic details in the thoracic duct and jugulovenous junction but can play a role as a decision-making and a planning tool for subsequent lymphatic interventions.

Magnetic resonance lymphangiography: with or without contrast?

Lymphedema is an important medical issue around the world, caused by an anomalous collection of fluid in soft tissue due to congenital malformations or stenosis or obstruction of lymphatic vessels. Magnetic resonance lymphangiography (MRL) is an emerging technique focused on noninvasive or minimally invasive imaging of lymphatics with the goal to diagnose and treat lymphedema. This review will briefly discuss lymphatic imaging starting with lymphography and radionuclide lymphoscintigraphy up to the newest methods, focusing on MRL, a rising technique, and highlighting the technical aspects fundamental for achieving high-resolution MRL.

Use of Propranolol in the Treatment of Chylous Effusions in Infants

Chylothorax and chyloperitoneum are rare in infants and challenging to definitively diagnose by using current criteria extrapolated from the adult population. They can be of primary or secondary etiologies, including congenital lymphatic malformations and postoperatively, after cardiothoracic or abdominal surgery. Current first-line management consists of bowel rest, parenteral nutrition, and a modified diet of medium-chain triglycerides but can often take weeks to be effective. Off-label use of octreotide has been reported in numerous case studies for the management of chylous effusions. However, there are no definitive neonatal data available regarding dosing, safety, and efficacy; moreover, octreotide has a side effect profile that been linked to serious morbidities, such as pulmonary hypertension and necrotizing enterocolitis. Propranolol, commonly used for the treatment of infantile hemangiomas, is currently gaining interest as a novel therapy for chylous effusions. In this case series review, we describe the use of propranolol in 4 infants with presumed chylous effusions: 1 with congenital pleural effusions and 3 infants who developed postoperative chylothorax and/or chylous ascites. Clinical improvement was noted within a few days of initiating oral propranolol, and the maximum dose used in our cases was 6 mg/kg per day. In previous case reports, researchers describe the use of oral propranolol in infants with chylous effusions, with the dose used ranging from 0.5 to 4 mg/kg per day. However, this is the first case series in which researchers report its use exclusively in infants with chylothorax and chyloperitoneum. Although further research is needed to establish safety and efficacy, our experiences suggest that propranolol could be an acceptable treatment option for chylous effusions in infants.

Advances in Lymphedema

Lymphedema is a common, complex, and inexplicably underappreciated human disease. Despite a history of relative neglect by health care providers and by governmental health care agencies, the last decade has seen an explosive growth of insights into, and approaches to, the problem of human lymphedema. The current review highlights the significant advances that have occurred in the investigative and clinical approaches to lymphedema, particularly over the last decade. This review summarizes the progress that has been attained in the realms of genetics, lymphatic imaging, and lymphatic surgery. Newer molecular insights are explored, along with their relationship to future molecular therapeutics. Growing insights into the relationships among lymphedema, obesity, and other comorbidities are important to consider in current and future responses to patients with lymphedema.

Systematic Review of Magnetic Resonance Lymphangiography From a Technical Perspective

BACKGROUND

Clinical examination and lymphoscintigraphy are the current standard for investigating lymphatic function. Magnetic resonance imaging (MRI) facilitates three-dimensional (3D), nonionizing imaging of the lymphatic vasculature, including functional assessments of lymphatic flow, and may improve diagnosis and treatment planning in disease states such as lymphedema.

PURPOSE

To summarize the role of MRI as a noninvasive technique to assess lymphatic drainage and highlight areas in need of further study.

STUDY TYPE

Systematic review.

POPULATION

In October 2019, a systematic literature search (PubMed) was performed to identify articles on magnetic resonance lymphangiography (MRL).

FIELD STRENGTH/SEQUENCE

No field strength or sequence restrictions.

ASSESSMENT

Article quality assessment was conducted using a bespoke protocol, designed with heavy reliance on the National Institutes of Health quality assessment tool for case series studies and Downs and Blacks quality checklist for health care intervention studies.

STATISTICAL TESTS

The results of the original research articles are summarized.

RESULTS

From 612 identified articles, 43 articles were included and their protocols and results summarized. Field strength was 1.5 or 3.0 T in all studies, with 25/43 (58%) employing 3.0 T imaging. Most commonly, imaging of the peripheries, upper and lower limbs including the pelvis (32/43, 74%), and the trunk (10/43, 23%) is performed, including two studies covering both regions. Imaging protocols were heterogenous; however, T2 -weighted and contrast-enhanced T1 -weighted images are routinely acquired and demonstrate the lymphatic vasculature. Edema, vessel, quantity and morphology, and contrast uptake characteristics are commonly reported indicators of lymphatic dysfunction.

DATA CONCLUSION

MRL is uniquely placed to yield large field of view, qualitative and quantitative, 3D imaging of the lymphatic vasculature. Despite study heterogeneity, consensus is emerging regarding MRL protocol design. MRL has the potential to dramatically improve understanding of the lymphatics and detect disease, but further optimization, and research into the influence of study protocol differences, is required before this is fully realized.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY: Stage 2.

Novel interventional radiological management for lymphatic leakages after gynecologic surgery: lymphangiography and embolization

Post-operative lymphatic leakage is a common complication of a radical gynecologic surgery involving aggressive lymph node dissection. Its manifestation varies from asymptomatic lymphoceles to life-threatening chylous ascites. In the past, nuclear medicine lymphoscintigraphy was the sole imaging modality for the confirmation of the leakage, of which application is limited due to its poor spatial resolution. While a conservative treatment with percutaneous drainage was the mainstream treatment method, surgical exploration was the last resort for the recalcitrant leakages. Recently, there have been a series of innovations in the field of interventional radiology, including intranodal Lipiodol^® lymphangiography, dynamic magnetic resonance (MR) lymphangiography, lymphatic embolization, and mesenteric lymph node lymphangiography. Intranodal Lipiodol^® lymphangiography provides very reliable and secure access to the lymphatic system, while requiring only fundamental skills and equipment available to all interventional radiologists. Besides, Lipiodol^® is being received a spotlight for its potential therapeutic effects on refractory lymphatic leakage. Dynamic MR lymphangiography plays a vital role in the diagnosis and management of non-traumatic lymphatic diseases, as well as in the post-operative lymphatic leakage with its superior contrast, spatial and temporal resolution. Lymphatic embolization is a technique of using N-BCA glue, a liquid embolic agent, for lymphatic leakages. It can be further described as lymphopseudoaneurysm (LPA) embolization or lymph node embolization, according to which structure is being embolized. Lymphatic embolization opened a new realm of possibilities in the field of interventional lymphology, resulting in the development of treatment approaches for chylous ascites and lymphoceles. Mesenteric lymph node lymphangiography offers the opacification of the upstream mesenteric chylous lymphatic system and can detect lymphatic leakage from the intestinal trunk or the more proximal parts of the mesenteric lymphatic system. With the advent of these latest interventional radiological techniques, more comprehensive approaches to the management of recalcitrant post-operative lymphatic leakages have been enabled.

Dynamic contrast-enhanced magnetic resonance lymphangiography in pediatric patients with central lymphatic system disorders

Central conducting lymphatics (CCLs) disorders represent a broad spectrum of clinical entities ranging from self-limiting traumatic leaks treated by conservative strategies, to complex lymphatic circulation abnormalities that are progressive and unresponsive to currently available treatments. Dynamic contrast-enhanced magnetic resonance lymphangiography (DCMRL) performed by intranodal injection of gadolinium-based contrast material is a recently developed technique which allows a minimally invasive evaluation of the CCL abnormalities providing a dynamic assessment of lymph flow and its pathways. In our institution, DCMRL is performed after bilateral cannulation of inguinal lymph nodes, using a MR protocol which includes volumetric 3D T2-SPACE (sampling perfection with application-optimized contrasts using different flip-angle evolution) and free-breathing respiratory navigated sequence and TWIST (time-resolved angiography with Interleaved stochastic trajectories) MR angiography sequence, during intranodal injection of paramagnetic contrast medium. Although DCMRL applications in clinical practice are still improving, a minimally invasive assessment of lymphatic pathways is particularly important both in pediatric patients with primitive lymphatic system disorders and in children with complex congenital heart disease associated with CCL impairment.

Nontraumatic Chylothorax: Nonenhanced MR Lymphography

Chylothorax is a rare cause of pleural effusion, secondary to accumulation of lymph in the pleural space. Diagnosis is based on the triglyceride and cholesterol content of pleural fluid obtained with thoracentesis. Because the lymphatic system plays an essential role in fat absorption and immune response, lymphatic leak associated with chylothorax may cause life-threatening malnutrition and immunodeficiency. Chylothorax is usually described as traumatic or nontraumatic. The main cause of chylothorax is traumatic, typically postsurgical, secondary to iatrogenic direct puncture of the thoracic duct during thoracic surgery. Causes of nontraumatic chylothorax include a wide range of differential diagnoses. Lymphoma and thoracic malignancies are the most common causes and are responsible for chylothorax by extrinsic compression or invasion of the thoracic duct. Other rare causes include primary and secondary diffuse lymphatic diseases, responsible for chylothorax by lymphatic vessel wall dysfunction. Imaging the lymphatic system remains a challenge in the days of modern imaging. Nonenhanced MR lymphography is a noninvasive technique based on heavily T2-weighted sequences, thus enabling visualization of the lymphatic circulation. This technique allows diagnosis and differential diagnosis, evaluation of disease severity, and guidance of therapeutic management in nontraumatic chylothorax. Furthermore, it may offer radiologic classification of primary lymphatic diseases on the basis of morphologic features of lymphatic vessels. The authors describe the anatomy and physiology of the thoracic lymphatic system, present the technique of nonenhanced MR lymphography, and discuss pathophysiologic mechanisms and imaging features in different causes of nontraumatic chylothorax. ^©RSNA, 2020.

Lymphatic Imaging: Current Noninvasive and Invasive Techniques

After nearly disappearing, invasive lymphangiography not only has resurged, but new approaches have been developed to guide lymphatic interventions. At the same time, noninvasive lymphatic imaging is playing a larger role in the evaluation of lymphatic pathologies. Lymphangioscintigraphy, computed tomography lymphangiography, and magnetic resonance lymphangiography are increasingly being used as alternatives to invasive diagnostic lymphangiography. The purpose of this article is to review current invasive and noninvasive lymphatic imaging techniques.

Application of imaging in lymphedema surgical therapies

Lymphedema is a chronic, progressive disease caused by primary or secondary reasons. It is currently uncurable and conservative compression therapy is generally applied. Lymphovenous anastomosis and vascularized lymph node transfer (VLNT) are two main surgical treatment that are used in addition to conservative therapy. Lymphovenous anastomosis involves the anastomosing remaining functional lymphatic vessels to vein. When the lymphatic vessels are greatly damaged and in no case can they be used for anastomosis, VLNT provide the affected area with lymph nodes from elsewhere to restore the drainage function. During all these procedures, a clear image to identify related lymphatic structures and venous vessels can be greatly useful for preoperative planning, intraoperative navigation, and postoperative evaluation. Lymphoscintigraphy used to be the gold standard in evaluating lymphedema and mapping lymphatic systems. But due to the downside of radiation, invasive operation and complication, other modalities are gaining attention. In this article, we reviewed the application of Indocyanine green (ICG) lymphography, ultrasound, magnetic resonance lymphography (MRL), and single-photon emission computed tomography-computed tomography (SPECT-CT) in the field of surgical therapy in lymphedema.

Magnetic Resonance Lymphangiography of the Central Lymphatic System: Technique and Clinical Applications

Magnetic resonance lymphangiography (MRL) is a noninvasive imaging technique that can be used in the management of lymphatic disorders to delineate the central lymphatic system for treatment planning. This article reviews the MRL technique, its advantages, limitations, indications, and impact on patient management. Level of Evidence 5 Technical Efficacy Stage 3 J. MAGN. RESON. IMAGING 2021;53:374-380.

MR Lymphangiography

림프부종의 수술적 치료는 최근 늘어나고 있으며 그에 따른 림프관 평가를 위해 자기공명영상 획득이 증가하고 있다. 전통적인 T2 강조영상에서부터 삼차원 영상에 이르기까지 많은 발전이 이루어지고 있는 분야이다. 삼차원 영상으로는 spoiled gradient echo 영상이 있고 그 변형기법들이 시행되고 있으며 영상에 필수적인 지방억제기법은 최근 mDixon 기법이 각광받고 있다.

Clinical approach and review of causes of a chylothorax

A chylothorax, also known as chylous pleural effusion, is an uncommon cause of pleural effusion with a wide differential diagnosis characterized by the accumulation of bacteriostatic chyle in the pleural space. The pleural fluid will have either or both triglycerides >110 mg/dL and the presence of chylomicrons. It may be encountered following a surgical intervention, usually in the chest, or underlying disease process. Management of a chylothorax requires a multidisciplinary approach employing medical therapy and possibly surgical intervention for post-operative patients and patients who have failed medical therapy. In this review, we aim to discuss the anatomy, fluid characteristics, etiology, and approach to the diagnosis of a chylothorax.

A Case of Adult T-Cell Leukemia/Lymphoma Complicated with Bilateral Chylothorax

We present the case of a 74-year-old Japanese woman who presented with dyspnea, a palpable right breast mass, and swollen right axillary lymph node. Imaging studies revealed bilateral pleural effusion and systemic lymph adenopathy and pleural fluid study showed high levels of triglycerides. A right inguinal lymph node biopsy disclosed malignant lymphoma cells that were human T-cell leukemia virus type 1 (HTLV-1) provirus DNA-positive, a condition endemic to patient's birthplace, by the Southern blot hybridization method. She was diagnosed as having adult T-cell leukemia/lymphoma (ATL) with chylothorax. After commencing chemotherapy for ATL, her chylothorax disappeared and swollen lymph nodes reduced remarkably, indicating an association between the chylothorax and ATL. Bilateral chylothorax is a relatively rare condition associated with such nontraumatic causes as ATL. Clinicians should therefore bear chylothorax in mind when encountering patients with pleural effusion. A detailed medical history can also enable prompt diagnosis and appropriate treatment.

The anatomy and physiology of the terminal thoracic duct and ostial valve in health and disease: potential implications for intervention

The thoracic duct (TD) transports lymph drained from the body to the venous system in the neck via the lymphovenous junction. There has been increased interest in the TD lymph (including gut lymph) because of its putative role in the promotion of systemic inflammation and organ dysfunction during acute and critical illness. Minimally invasive TD cannulation has recently been described as a potential method to access TD lymph for investigation. However, marked anatomical variability exists in the terminal segment and the physiology regarding the ostial valve and terminal TD is poorly understood. A systematic review was conducted using three databases from 1909 until May 2017. Human and animal studies were included and data from surgical, radiological and cadaveric studies were retrieved. Sixty-three articles from the last 108 years were included in the analysis. The terminal TD exists as a single duct in its terminal course in 72% of cases and 13% have multiple terminations: double (8.5%), triple (1.8%) and quadruple (2.2%). The ostial valve functions to regulate flow in relation to the respiratory cycle. The patency of this valve found at the lymphovenous junction opening, is determined by venous wall tension. During inspiration, central venous pressure (CVP) falls and the valve cusps collapse to allow antegrade flow of lymph into the vein. During early expiration when CVP and venous wall tension rises, the ostial valve leaflets cover the opening of the lymphovenous junction preventing antegrade lymph flow. During chronic disease states associated with an elevated mean CVP (e.g. in heart failure or cirrhosis), there is a limitation of flow across the lymphovenous junction. Although lymph production is increased in both heart failure and cirrhosis, TD lymph outflow across the lymphovenous junction is unable to compensate for this increase. In conclusion the terminal TD shows marked anatomical variability and TD lymph flow is controlled at the ostial valve, which responds to changes in CVP. This information is relevant to techniques for cannulating the TD, with the aid of minimally invasive methods and high resolution ultrasonography, to enable longitudinal physiology and lymph composition studies in awake patients with both acute and chronic disease.

Unilateral pedal lymphangiography plus computed tomography angiography for location of persistent idiopathic chyle leakage not detectable by ordinary contrast computed tomography

Background

To identify the value of unilateral pedal lymphangiography (LPG) plus computed tomography angiography (CTA) in accurate depiction of persistent idiopathic chyluria undetectable by ordinary contrast CT.

Methods

Eighteen patients 44–63 years of age with persistent idiopathic chyluria who failed conservative management were included. Ordinary CT had not revealed a chyle leak. Cystoscopy, unilateral LPG, and post-LPG CT angiography (CTA) were sequentially performed. Ligation and stripping of the perirenal lymphatics were subsequently performed guided by lymphangiography and CTA.

Results

LPG and post-LPG CTA detected 17 unilateral and one bilateral chyle leaks in the 18 patients, with clear images of the communication of lymphatic vessels and the renal collecting or vascular system. The success rate was significantly better than cystoscopy (100% vs 50.0%, P = 0.005) or LPG alone (100% vs. 72.2%, P = 0.016). Chyluria resolved after surgery in all patients; no relapses were found.

Conclusions

LPG plus post-LPG CTA accurately characterized perirenal lymphangiectasia that was not demonstrated by routine contrast-enhanced CT or not suitable for magnetic resonance imaging. Despite of its invasiveness, this method is a good diagnostic alternative to LPG in patients with persistent chyluria requiring surgery.

Initial Clinical Experience with Dual-Agent Relaxation Contrast for Isolated Lymphatic Channel Mapping

Purpose To evaluate the clinical performance of dual-agent relaxation contrast (DARC) magnetic resonance (MR) lymphangiography compared with that of conventional MR lymphangiography in the creation of isolated lymphatic maps in patients with secondary lymphedema. Materials and Methods This retrospective study was approved by the institutional review board. The diagnostic quality of 42 DARC MR lymphangiographic studies was compared with that of 42 conventional MR lymphangiographic studies. Two independent readers rated venous contamination as absent, mild, or moderate to severe. Interreader agreement on venous contamination grades was assessed by using the linearly weighted Cohen κ statistic. The Mann-Whitney U test was used to compare the distribution of grades at each station between conventional MR lymphangiography and DARC MR lymphangiography for each reader separately. Results DARC MR lymphangiography had significantly less venous contamination than did conventional MR lymphangiography (P < .001). The two radiologists rated venous contamination as moderate to severe in 64% (27 of 42) and 69% (29 of 42) of distal limbs, 23% (10 of 42) of midlimbs, and 2% (one of 42) and 9% (four of 42) of proximal limbs at conventional MR lymphangiography compared with 0% (0 of 42) of distal limbs, 2% (one of 42) of midlimbs, and 0% (0 of 42) of proximal limbs at DARC MR lymphangiography. Lymphatic signal was partially attenuated (median 45% decrease) when longer echo times were used for venous suppression, but it did not subjectively degrade diagnostic quality. Conclusion DARC MR lymphangiography yields isolated lymphatic maps through nulling of venous contamination, thereby simplifying diagnostic interpretation and communication with surgical colleagues. ^© RSNA, 2017.