Swing segment stenosis: An unresolved challenge.

The native arteriovenous fistula is considered the gold standard among all dialysis access options. Compared with alternatives such as grafts and central venous catheters, their use is associated with a lower risk of infective and thrombotic complications. This leads to better patient outcomes and reduced healthcare-associated costs. Recognizing these advantages, there is a global drive to increase the creation and use of such fistulas in hemodialysis patients. Swing segment stenosis is a common problem encountered with the creation and use of these fistulas that can hurt their maturation and longevity. A "swing segment" in an arteriovenous fistula is defined as a segment of vein that pursues a sharp, curved course. Due to poorly understood reasons, these swing segments tend to develop stenotic lesions that are extremely challenging to treat. This review aims to provide an overview of the pathophysiology, incidence, management, and prevention of these swing segment lesions. We believe that such knowledge will be useful for clinicians who deal with dialysis access creation and maintenance.

Transplant Nephrectomy: Current Concepts.

Kidney transplantation is the gold standard treatment option for patients with endstage kidney disease. As the number of waitlisted patients increases, the gap between supply and demand for suitable donor kidneys keeps widening. The adoption of novel strategies that expand the donor pool has attenuated this issue to a certain degree, and this has led to a progressive increase in the number of annual transplants performed. As transplanted kidneys have a finite lifespan, there is a reciprocal rise in the number of patients who return to dialysis once their allograft fails. The clinicians involved in the management of such patients are left with the problem of managing the nonfunctioning allograft. The decision to undertake transplant nephrectomy (TN) in these patients is not straightforward. Allograft nephrectomy is a procedure that is associated with significant morbidity and mortality. It will have implications for the outcomes of the subsequent transplant. In this review, we aimed to compressively discuss the indications, techniques, and outcomes of TN, which is an integral component of the management of a failing allograft.

Investigating the relationship between class I HLA-specific immunoglobulin-G subclasses, Pan-IgG single antigen bead assays and complement mediated interference in sera from renal transplant recipients.

INTRODUCTION: Antibody mediated rejection is the leading cause of kidney transplant failure. Not all antibodies are harmful and some may be protective. Immunoglulin Gs, of which there are four subtypes, are detected by single antigen bead testing. The aims of this study were to characterise the IgG subclass profiles for class I HLA-specific antibodies in an uncensored post-transplant population and to determine the underlying relationship between reactivity patterns and MFI cut-offs with the pan-IgG assay. METHODS: Patients were recruited to the study who were transplanted in our centre between 2009 and 2014. Prospectively stored post-transplant serum initially underwent a Labscreen Mixed assay and those positive for class I HLA-specific antibody underwent standard SAB testing, EDTA, 1 in 10 dilution and IgG subclass modifications using the Luminex platform. A total of 4947 bead reactions from 51 patients were analysed. RESULTS: A 1 in 10 dilution was used as a comparator pan-IgG assay for summed subclass and individual subclass linear regression analyses. Using a dilution to standard assay ratio we characterised all reactions for prozone potential i.e. how likely there is to be inhibition related to complement complex formation. We stratified samples into degrees of association and were able to determine suggested MFI thresholds of Log 5.35 for the dilution assay and Log 5.05 for the summed subclass assay when considering a Log MFI of 6.9 (1000) in the standard assay. Using individual subclass dominant reactions (>70%) we were able to determine linear relationships between the 1 in 10 dilution pan-IgG assay and the individual subclass assays (excluding prozone potential reactions for IgG1/3) enabling us to suggest Log MFI thresholds of 5.03, 3.58, 4.3 and 4.05 respectively for IgG1-4. DISCUSSION: We recommend a 1 in 10 dilution as the optimum pan-IgG comparator assay for a subclass analysis. We advocate the utilisation of the summed subclass assay to determine overall relationships and potential subclass failures. Following others, we recommend serum pre-treatment of the subclass assays to mitigate prozone. We suggest cut-offs for each IgG subclass which should be used with caution given the many inhibitory influences which may include competitive inhibition for bead binding, IgM and IgA interference and under-representation of specific subclasses on the bead panel.

Investigating complement mediated interference in class I HLA-specific antibodies following renal transplantation.

INTRODUCTION: Single antigen bead testing (SAB) for HLA-specific antibody enables efficient organ allocation and aids in the diagnosis of antibody mediated rejection. In this retrospective cohort study, a population of kidney transplant recipients possessing HLA Class I antibodies was used to evaluate the best method for resolving complement interference, the so called "prozone" effect. The aim was to compare the use of EDTA versus a Biotin-Streptavidin Complex as methodological approaches for abating the prozone effect using a fixed 1 in 10 dilution as validation. METHODS: One hundred and seventeen patients transplanted in our centre between 2009 and 2014 were identified as having class I HLA-specific antibody(-ies) using a Labscreen® Mixed assay. Positive sera underwent class I HLA-specific SAB testing; for comparison a standard SAB with and without EDTA, BSC and dilution (1 in 10) modifications were utilised. Samples were processed on the Luminex platform generating 11,349 bead reactions for analysis. RESULTS: We identified sera from 23 patients giving rise to 170 bead reactions showing complement interference. Using linear modelling, we observed slightly higher MFIs on average in both EDTA and BSC modifications when compared to the standard assay, allowing the nominal threshold MFI of 2000 in the standard assay to be adjusted to 2097 and 2033 in the EDTA and BSC assays respectively. We calculated 99% prediction intervals to establish outlier bead reactions for each assay. The 1 in 10 dilution was used as a crosscheck for determining which prozone reactions were overcome by EDTA and BSC. Using ROC curve analysis, EDTA was found to be ~90% sensitive and 100% specific compared to BSC which was ~60% sensitive and 100% specific in ameliorating prozone positive reactions at the thresholds defined by linear models. DISCUSSION: Our data indicates that both EDTA and BSC are suitable assays in overcoming CMI. We recommend that all clinical laboratories adopt a validated assay designed specifically to abrogate CMI for all potential renal transplant recipients, as the standard assay is inhibited in nearly 20% of a post-transplant cohort.

Preservation of the donor pancreas for whole pancreas and islet transplantation.

Whole pancreas and islet cell transplantation are both reliant upon the procurement and preservation of a high quality donor pancreas for a successful outcome. In the climate of a reducing donor pool it is imperative that donor optimization, meticulous surgical retrieval and evidence based methods of preservation are practiced to ensure optimal graft quality. Moreover expanded criteria donors and novel methods of pancreas preservation have the potential to expand the number of usable grafts and increase the availability of these transplant modalities to suitable patients with diabetes. This article provides a review of the current literature surrounding donor management, surgical technique and the various technologies of organ preservation applicable to the donor pancreas.

Acute lower limb ischemia associated with use of an immersion suit.

External compression is a rare cause of acute lower limb ischemia. Workers required to wear immersion suits during helicopter simulation training are exposed to external compressive forces which can alter the hemodynamics in arterial bypass conduits. Herein a case of arterial thromboembolization to the lower limb following the wearing of an immersion suit, in a patient who had undergone arterial bypass surgery 13 yr previously is presented. The potential for this episode of acute leg ischemia being a direct result of the compressive forces exerted by the immersion suit and the possible implications for wearers of immersion suits following arterial graft surgery is discussed.

Current practices of donor pancreas allocation in the UK: future implications for pancreas and islet transplantation.

Recent refinements in technique mean islet cell transplantation offers the chance of a cure to an increasing patient cohort with diabetes. Such developments put pressure upon the scarce resource of donor organs, with potential competition between the modalities of cellular and solid organ transplantation. This questionnaire based study examines current patterns of donor pancreas procurement and use. Reasons for non procurement are studied together with the attitudes of transplant professionals to pancreas allocation. The minority of potentially useful pancreata are currently made available to either whole pancreas or islet transplant programs. Whilst professionals appreciate the role of each modality, there is a need to define criteria for pancreas allocation to avoid under use of donor organs.