Lymphatic network of kidney. I. Anatomic and physiologic considerations

Role of the Renal Lymphatic System in Heart Failure

PURPOSE OF REVIEW

The lymphatic system plays a major but overlooked role in maintaining fluid homeostasis. Given the unique fluid homeostasis functions of the kidneys, dysregulation of the renal lymphatic system underlies the development of self-propagating congestive pathomechanisms. In this review, we outline the roles of the renal lymphatic system in heart failure (HF).

RECENT FINDINGS

Studies have uncovered several pathomechanisms involving the renal lymphatic system in congestive states, such as impaired interstitial draining by the renal lymphatic system, impaired structure and valves of renal lymphatics, lymphatic-induced increase in renal reabsorption of water and sodium, and development of albuminuria with proteinuria-induced renal lymphangiogenesis. These self-propagating mechanisms result in "renal tamponade" with manifestations of cardiorenal syndrome and inappropriate renal response to diuretics. Dysregulation of the renal lymphatic system is integral to the development and progression of congestion in HF. Targeting renal lymphatics may provide a novel pathway to treat intractable congestion.

Mediators of Regional Kidney Perfusion during Surgical Pneumo-Peritoneum Creation and the Risk of Acute Kidney Injury—A Review of Basic Physiology

Acute kidney injury (AKI), especially if recurring, represents a risk factor for future chronic kidney disease. In intensive care units, increased intra-abdominal pressure is well-recognized as a significant contributor to AKI. However, the importance of transiently increased intra-abdominal pressures procedures is less commonly appreciated during laparoscopic surgery, the use of which has rapidly increased over the last few decades. Unlike the well-known autoregulation of the renal cortical circulation, medulla perfusion is modulated via partially independent regulatory mechanisms and strongly impacted by changes in venous and lymphatic pressures. In our review paper, we will provide a comprehensive overview of this evolving topic, covering a broad range from basic pathophysiology up to and including current clinical relevance and examples. Key regulators of oxidative stress such as ischemia-reperfusion injury, the activation of inflammatory response and humoral changes interacting with procedural pneumo-peritoneum formation and AKI risk will be recounted. Moreover, we present an in-depth review of the interaction of pneumo-peritoneum formation with general anesthetic agents and animal models of congestive heart failure. A better understanding of the relationship between pneumo-peritoneum formation and renal perfusion will support basic and clinical research, leading to improved clinical care and collaboration among specialists.

Pathophysiology of the Lymphatic System in Patients With Heart Failure: JACC State-of-the-Art Review

The removal of interstitial fluid from the tissues is performed exclusively by the lymphatic system. Tissue edema in congestive heart failure occurs only when the lymphatic system fails or is overrun by fluid leaving the vascular space across the wall of the capillaries into the interstitial space. This process is driven by Starling forces determined by hydrostatic and osmotic pressures and organ-specific capillary permeabilities to proteins of different sizes. In this review, we summarize current knowledge of the generation of lymph in different organs, the mechanics by which lymph is returned to the circulation, and the consequences of the inadequacy of lymph flow. We review recent advances in imaging techniques that have allowed for new research, diagnostic, and therapeutic approaches to the lymphatic system. Finally, we review how efforts to increase lymph flow have demonstrated potential as a viable therapeutic approach for refractory heart failure.

Renal Lymphatics: Anatomy, Physiology, and Clinical Implications

Renal lymphatics are abundant in the cortex of the normal kidney but have been largely neglected in discussions around renal diseases. They originate in the substance of the renal lobule as blind-ended initial capillaries, and can either follow the main arteries and veins toward the hilum, or penetrate the capsule to join capsular lymphatics. There are no valves present in interlobular lymphatics, which allows lymph formed in the cortex to exit the kidney in either direction. There are very few lymphatics present in the medulla. Lymph is formed from interstitial fluid in the cortex, and is largely composed of capillary filtrate, but also contains fluid reabsorbed from the tubules. The two main factors that contribute to renal lymph formation are interstitial fluid volume and intra-renal venous pressure. Renal lymphatic dysfunction, defined as a failure of renal lymphatics to adequately drain interstitial fluid, can occur by several mechanisms. Renal lymphatic inflow may be overwhelmed in the setting of raised venous pressure (e.g., cardiac failure) or increased capillary permeability (e.g., systemic inflammatory response syndrome). Similarly, renal lymphatic outflow, at the level of the terminal thoracic duct, may be impaired by raised central venous pressures. Renal lymphatic dysfunction, from any cause, results in renal interstitial edema. Beyond a certain point of edema, intra-renal collecting lymphatics may collapse, further impairing lymphatic drainage. Additionally, in an edematous, tense kidney, lymphatic vessels exiting the kidney via the capsule may become blocked at the exit point. The reciprocal negative influences between renal lymphatic dysfunction and renal interstitial edema are expected to decrease renal function due to pressure changes within the encapsulated kidney, and this mechanism may be important in several common renal conditions.

Post-transplant lymphoceles: a critical look into the risk factors, pathophysiology and management

To define better the prevalence and pathophysiology of lymphoceles following renal transplantation, we prospectively evaluated 118 consecutive renal transplants performed in 115 patients (96 cadaveric, 22 living-related, 7 secondary and 111 primary). Ultrasonography was performed post-operatively and during rehospitalizations or whenever complications occurred. Perirenal fluid collections were identified in 43 patients (36%). Lymphoceles with a diameter of 5 cm. or greater were identified in 26 of 118 cases (22%). Eight patients (6.8%) had symptomatic lymphoceles requiring therapy. The interval for development of symptomatic lymphoceles was 1 week to 3.7 years (median 10 months). Risk factors for the development of lymphoceles were examined by univariate and multivariate analysis, and included patient age, sex, source of transplants (cadaver versus living-related donor), retransplantation, tissue match (HLA-B/DR), type of preservation, arterial anastomosis, occurrence of acute tubular necrosis-delayed graft function, occurrence of rejection, and use of high dose corticosteroids. Univariate analysis showed a significant risk for the development of lymphoceles in transplants with acute tubular necrosis-delayed graft function (odds ratio 4.5, p = 0.004), rejection (odds ratio 25.1 p < 0.001) and high dose steroids (odds ratio 16.4, p < 0.001). When applying multivariate analyses using stepwise logistic regression, only rejection was associated with a significant risk for lymphoceles (symptomatic lymphoceles--odds ratio 25.08, p = 0.0003, all lymphoceles--odds ratio 75.24, p < 0.0001). When adjusting for rejection, no other risk factor came close to being significant (least p = 0.4). Therapy included laparoscopic peritoneal marsupialization and drainage in 1 patient, incisional peritoneal drainage in 4 and percutaneous external drainage in 3 (infected). All symptomatic lymphoceles were successfully treated without sequelae to grafts or patients. We conclude that allograft rejection is the most significant factor contributing to the development of lymphoceles. Therapy of symptomatic lymphoceles should be individualized according to the presence or absence of infection.

Microradiographic demonstration of human intrarenal microlymphatic pathways

Renal lymphatics play a prominent role in physiological and pathologic states. However, intrarenal microlymphatic morphology has not been well established in humans. We have developed microangiographic techniques for studying microlymphatic morphology. Lymphatics were identified by location, presence of valves, and histologic characteristics in 4 patients (3 presented here and 1 reported previously), all of whom had congestive cardiac states. The renal lymphatics begin in the cortical interstitium near glomeruli and run adjacent to afferent arterioles and interlobular arteries. They drain into arcuate and interlobar vessels and then into hilar lymphatics. They also originate in and drain the medullary structures in the area of the vasa recta. Our study details the microlymphatic morphology in humans and confirms the similarity of human lymphatics to those studied extensively in pigs and dogs.

Acute perirenal lymphocele formation 8 years after renal transplantation

The majority of lymphoceles forming as a result of renal transplantation present or are detected within 6 months of surgery. A rare case of late presentation is reported, where the lymphocele developed 8 years after renal transplantation, due to leakage of lymph from the transplant kidney surface.

Lymphatic complications in renal allografts--a new look

The pathophysiology of lymphatic complications was evaluated in 10 patients as to the possible source of lymphatic fluid. Both the recipient's peripheral lymphatics and the allograft's lymphatics were found to contribute to lymphatic complications. The prevention of lymphoceles and lymphatic fistulas may be accomplished by careful ligation of both the recipient's and the allograft's lymphatics.

An analysis of 100 primary cadaver kidney transplants

A multifactorial analysis of 100 consecutive first cadaver kidney transplants was done to document the current status of this treatment for end stage renal disease and to determine the influence of the following variables on kidney losses owing to rejection: splenectomy, pre-transplant transfusions, transfusion at the transplantation, recipient sex, pre-transplant nephrectomy, donor and recipient A, B or O blood group, human leukocyte A and B antigen mismatches, kidney preservation method, donor treatment with methylprednisolone and cyclophosphamide, recipient treatment with antilymphocyte serum or antilymphoblast globulin and a low dose of steroid treatment for rejection. Pre-transplant splenectomy for leukopenia, 5 or more pre-transplant blood transfusions and pre-transplant transfusions without development of circulating cytotoxic antibodies significantly reduced kidney losses owing to rejection (p less than 0.05)., A low dose of steroid treatment for rejection resulted in a trend towards improved patient survival without sacrificing kidney graft survival. Clinical studies demonstrating decreases in kidney graft rejection should be controlled for pre-transplant blood transfusions and, possibly, for pre-transplant splenectomy for hypersplenism.