The Lymphatic Vasculature in the 21st Century: Novel Functional Roles in Homeostasis and Disease.

Mammals have two specialized vascular circulatory systems: the blood vasculature and the lymphatic vasculature. The lymphatic vasculature is a unidirectional conduit that returns filtered interstitial arterial fluid and tissue metabolites to the blood circulation. It also plays major roles in immune cell trafficking and lipid absorption. As we discuss in this review, the molecular characterization of lymphatic vascular development and our understanding of this vasculature's role in pathophysiological conditions has greatly improved in recent years, changing conventional views about the roles of the lymphatic vasculature in health and disease. Morphological or functional defects in the lymphatic vasculature have now been uncovered in several pathological conditions. We propose that subtle asymptomatic alterations in lymphatic vascular function could underlie the variability seen in the body's response to a wide range of human diseases.

Winning the Microbial Battle, but Not the War.

An effective immune response leads to rapid elimination of infectious agents, with seemingly little long-term impairment to the host. New findings by Morais da Fonseca et al. reveal that acute infections may result in permanent disruption of tissue homeostasis and immune dysfunction, long after clearance of a pathogen.

Microbiota-Dependent Sequelae of Acute Infection Compromise Tissue-Specific Immunity.

Infections have been proposed as initiating factors for inflammatory disorders; however, identifying associations between defined infectious agents and the initiation of chronic disease has remained elusive. Here, we report that a single acute infection can have dramatic and long-term consequences for tissue-specific immunity. Following clearance of Yersinia pseudotuberculosis, sustained inflammation and associated lymphatic leakage in the mesenteric adipose tissue deviates migratory dendritic cells to the adipose compartment, thereby preventing their accumulation in the mesenteric lymph node. As a consequence, canonical mucosal immune functions, including tolerance and protective immunity, are persistently compromised. Post-resolution of infection, signals derived from the microbiota maintain inflammatory mesentery remodeling and consequently, transient ablation of the microbiota restores mucosal immunity. Our results indicate that persistent disruption of communication between tissues and the immune system following clearance of an acute infection represents an inflection point beyond which tissue homeostasis and immunity is compromised for the long-term. VIDEO ABSTRACT.

Congenital Vascular and Lymphatic Diseases.

Over the past several centuries, the integration of contemporary medical techniques and innovative technologies, like genetic sequencing, have played a pivotal role in enhancing our comprehension of congenital vascular and lymphatic disorders. Nonetheless, the uncommon and complex characteristics of these disorders, especially considering their formation during the intrauterine stage, present significant obstacles in diagnosis and treatment. Here, we review the intricacies of these congenital abnormalities, offering an in-depth examination of key diagnostic approaches, genetic factors, and therapeutic methods.

Genetic causes of lymphatic disorders: recent updates on the clinical and molecular aspects of lymphatic disease.

PURPOSE OF REVIEW: The lymphatic system facilitates several key functions that limit significant morbidity and mortality. Despite the impact and burden of lymphatic disorders, there are many remaining disorders whose genetic substrate remains unknown. The purpose of this review is to provide an update on the genetic causes of lymphatic disorders, while reporting on newly proposed clinical classifications of lymphatic disease. RECENT FINDINGS: We reviewed several new mutations in genes that have been identified as potential causes of lymphatic disorders including: MDFIC, EPHB 4 , and ANGPT2. Furthermore, the traditional St. George's Classification system for primary lymphatic anomalies has been updated to reflect the use of genetic testing, both as a tool for the clinical identification of lymphatic disease and as a method through which new sub-classifications of lymphatic disorders have been established within this framework. Finally, we highlighted recent clinical studies that have explored the impact of therapies such as sirolimus, ketoprofen, and acebilustat on lymphatic disorders. SUMMARY: Despite a growing body of evidence, current literature demonstrates a persistent gap in the number of known genes responsible for lymphatic disease entities. Recent clinical classification tools have been introduced in order to integrate traditional symptom- and time-based diagnostic approaches with modern genetic classifications, as highlighted in the updated St. George's classification system. With the introduction of this novel approach, clinicians may be better equipped to recognize established disease and, potentially, to identify novel causal mutations. Further research is needed to identify additional genetic causes of disease and to optimize current clinical tools for diagnosis and treatment.

Anesthesia-induced Lymphatic Dysfunction.

General anesthetics adversely alters the distribution of infused fluid between the plasma compartment and the extravascular space. This maldistribution occurs largely from the effects of anesthetic agents on lymphatic pumping, which can be demonstrated by macroscopic fluid kinetics studies in awake versus anesthetized patients. The magnitude of this effect can be appreciated as follows: a 30% reduction in lymph flow may result in a fivefold increase of fluid-induced volume expansion of the interstitial space relative to plasma volume. Anesthesia-induced lymphatic dysfunction is a key factor why anesthetized patients require greater than expected fluid administration than can be accounted for by blood loss, urine output, and insensible losses. Anesthesia also blunts the transvascular refill response to bleeding, an important compensatory mechanism during hemorrhagic hypovolemia, in part through lymphatic inhibition. Last, this study addresses how catecholamines and hypertonic and hyperoncotic fluids may mobilize interstitial fluid to mitigate anesthesia-induced lymphatic dysfunction.

MR Lymphangiography in Lymphatic Disorders: Clinical Applications, Institutional Experience, and Practice Development.

Lymphatic flow and anatomy can be challenging to study, owing to variable lymphatic anatomy in patients with diverse primary or secondary lymphatic pathologic conditions and the fact that lymphatic imaging is rarely performed in healthy individuals. The primary components of the lymphatic system outside the head and neck are the peripheral, retroperitoneal, mesenteric, hepatic, and pulmonary lymphatic systems and the thoracic duct. Multiple techniques have been developed for imaging components of the lymphatic system over the past century, with trade-offs in spatial, temporal, and contrast resolution; invasiveness; exposure to ionizing radiation; and the ability to obtain information on dynamic lymphatic flow. More recently, dynamic contrast-enhanced (DCE) MR lymphangiography (MRL) has emerged as a valuable tool for imaging both lymphatic flow and anatomy in a variety of congenital and acquired primary or secondary lymphatic disorders. The authors provide a brief overview of lymphatic physiology, anatomy, and imaging techniques. Next, an overview of DCE MRL and the development of an MRL practice and workflow in a hybrid interventional MRI suite incorporating cart-based in-room US is provided, with an emphasis on multidisciplinary collaboration. The spectrum of congenital and acquired lymphatic disorders encountered early in an MRL practice is provided, with emphasis on the diversity of imaging findings and how DCE MRL can aid in diagnosis and treatment of these patients. Methods such as DCE MRL for assessing the hepatic and mesenteric lymphatic systems and emerging technologies that may further expand DCE MRL use such as three-dimensional printing are introduced. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

Anesthetic challenges in patients with multicompartmental lymphatic failure after Fontan palliation undergoing transcatheter thoracic duct decompression.

Lymphatic flow abnormalities are central to the development of protein losing enteropathy, plastic bronchitis, ascites and pleural effusions in patients palliated to the Fontan circulation. These complications can occur in isolation or multicompartmental (two or more). The treatment of multicompartmental lymphatic failure aims at improving thoracic duct drainage. Re-routing the innominate vein to the pulmonary venous atrium decompresses the thoracic duct, as atrial pressure is lower than systemic venous pressure in Fontan circulation. Transcatheter thoracic duct decompression is a new minimally invasive procedure that involves placing covered stents from the innominate vein to the atrium. Patients undergoing this procedure require multiple general anesthetics, presenting challenges in managing the sequelae of disordered lymphatic flow superimposed on Fontan physiology. We reviewed the first 20 patients at the Center for Lymphatic Imaging and Intervention at a tertiary care children's hospital presenting for transcatheter thoracic duct decompression between March 2018 and February 2023. The patients ranged in age from 3 to 26 years. The majority had failed prior catheter-based lymphatic intervention, including selective embolization of abnormal lympho-intestinal and lympho-bronchial connections to treat lymphatic failure in a single compartment. Fourteen had failure in three lymphatic compartments. Patients were functionally impaired (ASA 3-5) with significant comorbidities. Concurrent with thoracic duct decompression, three patients required fenestration closure for the resultant decrease in oxygen saturation. Ten patients had improvement in symptoms, seven had no changes and three have limited follow up. Five (25%) of these patients were deceased as of January 2024 due to non-lymphatic complications from Fontan failure.

The use of superficial circumflex iliac perforator (SCIP) pedicle vein for lymphovenous anastomosis to treat inguinal lymphatic fistula: A case report.

The management of lymphatic fistulas following surgical procedures, in particular after inguinal lymphadenectomy, represents a significant clinical challenge. The current case report shows the novel use of the superficial circumflex iliac perforator (SCIP) pedicle vein for lymphovenous anastomosis (LVA) to treat a chronic inguinal lymphatic fistula in a 58-year-old male patient. This patient had developed a persistent lymphorrhea and wound dehiscence after a right inguinal lymph node biopsy performed for oncological reasons 1.5 months before. Pre-operative assessment with indocyanine green (ICG) lymphography confirmed a substantial lymphatic contribution to the wound discharge, thus guiding the surgical strategy. During the procedure, a pedicled tissue segment containing the SCIV was dissected and utilized to fill the wound's dead space and facilitate LVA with the leaking lymphatic vessel. Notably, a coupler device was employed for the anastomosis due to the large caliber of the lymphatic vessel involved, a technique not commonly reported in lymphatic surgeries. The result of the procedure was successful, with intra-operative ICG imaging confirming the patency of the anastomosis. After surgery the wound healed without complications. This case illustrates the potential of SCIV employment in lymphatic fistula repair in the inguinal region. While further research is needed to validate these findings, this report provides an unconventional approach to a relatively common problem in clinical practice.

Comparing easywrap with six other adjustable wraps for compression therapy in venous and lymphatic disease by variation in pressure, stiffness and elasticity.

BACKGROUND: There is no clear guidance or comprehensive comparative evidence to help clinicians select between adjustable wraps for compression therapy. However, adjustable wraps could be compared with three metrics used for compression bandages: variation in pressure, stiffness and elasticity. AIMS: To determine whether easywrap (Haddenham Healthcare) had lower standard deviation (SD) in lying pressure, greater static stiffness index (SSI) and/or a greater mean elongation ratio than six other adjustable wraps. METHODS: In this preliminary exploratory study, seven adjustable wraps were tested in vivo 20 times each (140 tests in total), on 20 people (with a variable number of readings per participant), to give the SD in lying pressure and mean SSI. The same wraps were tested in vitro five times each to give the mean elongation ratio. FINDINGS: Of all seven adjustable wraps, easywrap had the second lowest SD in lying pressure at 5.9 mmHg, compared with 8.9 mmHg overall; the highest mean SSI at 13.2 mmHg, compared with 9.5 mmHg overall; and the highest mean elongation ratio at 137.0%, compared with 107.1% overall. CONCLUSIONS: These metrics suggest that easywrap has clinical advantages over other adjustable wraps. A lower variation in lying pressure suggests more consistent application of pressures within intended therapeutic levels. Higher SSI indicates greater resistance to stretching, which is linked to improved venous function and oedema reduction. Higher elongation ratio demonstrates greater tensile strength, which should maintain therapeutic pressure for longer without readjustment.

Comparing easywrap with six other adjustable wraps for compression therapy in venous and lymphatic disease by variation in pressure, stiffness and elasticity.

BACKGROUND: There is no clear guidance or comprehensive comparative evidence to help clinicians select between adjustable wraps for compression therapy. However, adjustable wraps could be compared with three metrics used for compression bandages: variation in pressure, stiffness and elasticity. AIMS: To determine whether easywrap (Haddenham Healthcare) had lower standard deviation (SD) in lying pressure, greater static stiffness index (SSI) and/or a greater mean elongation ratio than six other adjustable wraps. METHODS: In this preliminary exploratory study, seven adjustable wraps were tested in vivo 20 times each (140 tests in total), on 20 people (with a variable number of readings per participant), to give the SD in lying pressure and mean SSI. The same wraps were tested in vitro five times each to give the mean elongation ratio. FINDINGS: Of all seven adjustable wraps, easywrap had the second lowest SD in lying pressure at 5.9 mmHg, compared with 8.9 mmHg overall; the highest mean SSI at 13.2 mmHg, compared with 9.5 mmHg overall; and the highest mean elongation ratio at 137.0%, compared with 107.1% overall. CONCLUSIONS: These metrics suggest that easywrap has clinical advantages over other adjustable wraps. A lower variation in lying pressure suggests more consistent application of pressures within intended therapeutic levels. Higher SSI indicates greater resistance to stretching, which is linked to improved venous function and oedema reduction. Higher elongation ratio demonstrates greater tensile strength, which should maintain therapeutic pressure for longer without readjustment.

Bilateral axillary web syndrome in a patient with primary lymphoedema of upper limbs and non-Hodgkin lymphoma.

Primary lymphoedema, axillary web syndrome (AWS) and yellow nail syndrome may be related. Mr B is a 66-year-old gentleman with genital lymphoedema and lymphoedema of all four extremities. In 2023, he was diagnosed with non-Hodgkin lymphoma and also underwent cardiac surgery. In November 2023, he completed an inpatient rehabilitation at the Földi clinic in Germany, where he received intensive treatment for his lymphoedema and was also diagnosed with bilateral AWS. The presence of AWS in a patient with primary lymphoedema and no history of axillary surgery is unique. Although AWS typically presents after axillary surgery, this case highlights that it can also occur in patients without lymph node surgery. While the precise cause of this presentation of AWS is not known, it may be connected to yellow nail syndrome or potentially the recent chemotherapy treatment. This article will describe the clinical case, highlighting the need for further research on AWS present in primary lymphoedema.

[A Case of Lymphorrhea after Radical Cystectomy Treated by Ultrasound-Guided Inguinal Intranodal Lymphangiography].

A 76-year-old woman was diagnosed with invasive bladder cancer and underwent cystectomy, bilateral external iliac, internal iliac and obturator lymph node dissection, and bilateral cutaneous ureterostomy. Pathological findings showed no lymph node metastasis ; however, the patient had lower abdominal pain and fever from the 14th postoperative day, and computed tomography (CT) revealed fluid retention in the pelvis. Retrograde pyelography showed no leakage from the urinary tract, and a drain was placed after percutaneous puncture of the pelvic cavity. There was copious drainage fluid and its nature and composition suggested lymphorrhea. Ultrasound-guided intranodal lymphangiography revealed contrast material leakage from the bilateral lymph node dissection sites. After lymphangiography, drainage from the drain decreased. Despite the drainage being minimal yet persistent, sclerotherapy was performed, the drain was removed and the patient was discharged. After discharge, there was leakage from the site of urethral extraction, and CT revealed recurrent lymph leakage. The patient was readmitted, and a second lymphangiography was performed. The leakage from the site of urethral extraction gradually decreased, and the patient was discharged on the 59th postoperative day. CT after discharge confirmed that the lymphorrhea had shrunk in size, and there has been no recurrence since then. Lymphangiography is a promising treatment option for lymphorrhea after pelvic surgery.

Lymphatic Vasculature: An Emerging Therapeutic Target and Drug Delivery Route.

The lymphatic system has received increasing scientific and clinical attention because a wide variety of diseases are linked to lymphatic pathologies and because the lymphatic system serves as an ideal conduit for drug delivery. Lymphatic vessels exert heterogeneous roles in different organs and vascular beds, and consequently, their dysfunction leads to distinct organ-specific outcomes. Although studies in animal model systems have led to the identification of crucial lymphatic genes with potential therapeutic benefit, effective lymphatic-targeted therapeutics are currently lacking for human lymphatic pathological conditions. Here, we focus on the therapeutic roles of lymphatic vessels in diseases and summarize the promising therapeutic targets for modulating lymphangiogenesis or lymphatic function in preclinical or clinical settings. We also discuss considerations for drug delivery or targeting of lymphatic vessels for treatment of lymphatic-related diseases. The lymphatic vasculature is rapidly emerging as a critical system for targeted modulation of its function and as a vehicle for innovative drug delivery.

Case 311: Generalized Lymphatic Anomaly.

HISTORY: A 14-year-old boy presented with asthenia, low back pain, and abdominal distention. The onset of symptoms was slow and progressive over a few months. The patient had no contributing past medical history. At physical examination, all vital signs were normal. Only pallor and positive fluid wave test results were noted; there was no lower limb edema, mucocutaneous lesions, or palpable lymph node enlargement. Laboratory work-up revealed a decreased hemoglobin concentration of 9.3 g/dL (normal range, 12-16 g/dL) and a decreased hematocrit level of 29.8% (normal range, 37%-45%), but all other laboratory values were normal. Contrast-enhanced CT of the chest, abdomen, and pelvis was performed.

Expression of A20 by dendritic cells preserves immune homeostasis and prevents colitis and spondyloarthritis.

Dendritic cells (DCs), which are known to support immune activation during infection, may also regulate immune homeostasis in resting animals. Here we show that mice lacking the ubiquitin-editing molecule A20 specifically in DCs spontaneously showed DC activation and population expansion of activated T cells. Analysis of DC-specific epistasis in compound mice lacking both A20 and the signaling adaptor MyD88 specifically in DCs showed that A20 restricted both MyD88-independent signals, which drive activation of DCs and T cells, and MyD88-dependent signals, which drive population expansion of T cells. In addition, mice lacking A20 specifically in DCs spontaneously developed lymphocyte-dependent colitis, seronegative ankylosing arthritis and enthesitis, conditions stereotypical of human inflammatory bowel disease (IBD). Our findings indicate that DCs need A20 to preserve immune quiescence and suggest that A20-dependent DC functions may underlie IBD and IBD-associated arthritides.

Understanding the next circulation: lymphatics and what the future holds.

PURPOSE OF REVIEW: The lymphatic system was previously considered the forgotten circulation because of an absence of adequate options for imaging and intervention. However, recent advances over the last decade have improved management strategies for patients with lymphatic disease, including chylothorax, plastic bronchitis, ascites, and protein-losing enteropathy. RECENT FINDINGS: New imaging modalities have enabled detailed visualization of lymphatic vessels to allow for a better understanding of the cause of lymphatic dysfunction in a variety of patient subsets. This sparked the development of multiple transcatheter and surgery-based techniques tailored to each patient based on imaging findings. In addition, the new field of precision lymphology has added medical management options for patients with genetic syndromes, who have global lymphatic dysfunction and typically do not respond as well to the more standard lymphatic interventions. SUMMARY: Recent developments in lymphatic imaging have given insight into disease processes and changed the way patients are managed. Medical management has been enhanced and new procedures have given patients more options, leading to better long-term results.

Characterization and treatment of thoracic duct obstruction in patients with lymphatic flow disorders.

PURPOSE: The contribution of thoracic duct obstruction to lymphatic flow disorders has not been well-characterized. We describe imaging findings, interventions, and outcomes in patients with suspected duct obstruction by imaging or a lympho-venous pressure gradient (LVPG). MATERIALS AND METHODS: Clinical, imaging, and interventional data, including the LVPG, of patients with flow disorders and imaging features of duct obstruction who underwent lymphatic intervention were retrospectively reviewed, collated, and analyzed with descriptive statistics. RESULTS: Eleven patients were found to have obstruction, median age 10.4 years (interquartile range: 8-14.9 years). Pleural effusions were seen in 8/11 (72%), ascites in 8/11 (72%), both in 5/11 (45%), and protein-losing enteropathy in 5 (45%). Eight patients (72%) had congenital heart disease. The most common site of obstruction was at the duct outlet in 7/11 patients (64%). Obstruction was secondary to extrinsic compression or ligation 4 patients (36%). Nine patients (82%) underwent interventions, with balloon dilation in 7/9 (78%), massive lymphatic malformation drainage and sclerotherapy in 1, and lympho-venous anastomosis in 1. There was resolution of symptoms in 7/9 (78% who underwent intervention, with worsening in 1 patient and no change in 1. In these patients, preprocedure mean LVPG was 7.9 ± 5.7 mmHg and postprocedure gradient was 1.6 ± 1.9 mmHg (p = 0.014). Five patients in this series underwent intervention solely to alleviate duct obstruction and in 4/5 (80%) this led to resolution of symptoms (p = 0.05). CONCLUSION: Duct obstruction may be seen in lymphatic flow disorders and can occur from intrinsic and extrinsic causes. Stenosis at the outlet was most common. Obstruction can be demonstrated by an elevated LVPG, and interventions to alleviate the obstruction can be beneficial.

Intranodal Glue Embolization for Postoperative Lymphatic Leaks in the Groin and Pelvis: Comparison with Sclerotherapy.

PURPOSE: To compare the effectiveness of and adverse events related to intranodal glue embolization (IGE) with those of intracavitary sclerotherapy for the treatment of postoperative groin and pelvic lymphatic leaks. MATERIALS AND METHODS: From November 2015 to July 2021, IGE for postoperative pelvic or groin lymphocele or lymphorrhea was performed in 33 patients. From January 2010 to July 2021, 28 patients with postoperative pelvic or groin lymphocele were treated with sclerosis alone. Clinical success was defined as resolution of drainage within 3 weeks of the last intervention performed without recurrence. Patients presenting >1 year after surgery or with <30 days of follow-up were excluded. Patients with lymphorrhea treated with IGE were not statistically compared with those in the sclerosis group because they were not eligible for sclerosis. RESULTS: Clinical success was similar between the groups (lymphocele IGE, 15/18, 83.3%, vs sclerosis, 15/23, 65.2% [P = .29]; lymphorrhea IGE, 8/9, 88.9%). The mean number of interventions performed to successfully treat a lymphocele was significantly higher in the sclerosis group (2.5 for sclerosis vs 1.3 for IGE; P = .003; lymphorrhea IGE, 1.0). The mean time to resolution was significantly longer for sclerosis than for IGE (27 vs 7 days; P = .002; 4 days for lymphorrhea IGE). There were no sclerosis-related adverse events and 2 IGE-related adverse events: (a) 1 case of mild lymphedema and (b) 1 case of nontarget embolization resulting in deep vein thrombosis. CONCLUSIONS: For treatment of postoperative pelvic and groin lymphoceles, IGE results in faster resolution with fewer interventions compared with sclerosis. IGE is also an effective treatment for postoperative groin lymphorrhea.

Review of Malpractice Litigation in the Diagnosis and Treatment of Venous & Lymphatic Disease.

BACKGROUND: Malpractice claims involving nonthrombotic venous and lymphatic diseases and interventions have not been reported previously. We investigated common reasons for litigation, medical specialties involved, patient injuries, and case outcomes in malpractice litigation involving venous and lymphatic disease. METHODS: Litigation cases entered into the Westlaw database from June 8th, 1984 to February 15th, 2018 were analyzed. Search terms included relevant words and phrases related to nonthrombotic venous, thoracic outlet syndrome, and lymphatic disease and treatment. Data on physician specialty, malpractice claims, and patient injuries jury outcomes, amount awarded to the plaintiff, and jury fees were collected and compared for each category. RESULTS: A total of 144 cases were identified. 41 cases involved varicose veins, 11 spider veins, 35 thoracic outlet syndrome (TOS), 17 other venous diseases, and 40 lymphatic diseases. Physician defendants were frequently vascular surgeons (23%) and general surgeons (15%). The majority of litigation claims involved "post-procedure complication" (77%), "lack of informed consent" (25%), "failure to diagnose & treat" (15%), and "intraoperative complications" (13%). The most common injuries were skin damage (27.8%), nerve damage (25%), and lymphedema (24%). Patient death occurred in 6% of cases. Out of venous malpractice cases with post-procedure complications, stab phlebectomy (27%) was the most common intervention followed by foam sclerotherapy (21%), rib resection (21%), laser spider vein removal (5%), and endovenous laser ablation therapy (EVLT)(3%). Of varicose vein cases, 15% included deep vein thrombosis or pulmonary embolism as post-procedure complications. In TOS rib resections, 65% of cases referenced nerve damage and 12% involved arterial injury. For lymphatic disease cases, general surgeons were frequently identified defendants (25%). Lymphedema (93%) and lymphangitis (7%) occurred as post-procedure complications after breast, gynecologic, orthopedic, and radiation procedures. A majority of complications occurred after breast cases (40%). Verdicts overall ruled in favor of the defendant in 71% (102/144) of cases and the plaintiff in 20% (29/144) of cases. Out of cases ruled in favor of the plaintiff, 31% were lymphatics, 24% varicose veins, and 24% TOS cases. Only 8% (12/144) of cases were settled and one outcome was unknown. The mean award was $820,193 (standard deviation SD $1,226,008, Range $12,853 - $6,500,000). CONCLUSIONS: The majority of venous and lymphatic litigation cases involve claims of post-procedure complications. Venous complications occurred after open and endovascular treatment of varicose veins, spider vein treatment, and surgical management of TOS. Lymphedema occurred after breast, oncology, and orthopedic procedures. These cases reflect opportunities for intervention to help potentially prevent litigation.