Influence of aspirin on early allograft thrombosis and chronic allograft nephropathy following renal transplantation

Effects of Aspirin on Kidney Biopsy Bleeding Complications: A Systematic Review and Meta-Analysis (PROSPERO 2021 CRD42021261005)

Postprocedural bleeding is the main complication of percutaneous kidney biopsy (PKB). Therefore, aspirin is routinely withheld in patients undergoing PKB to reduce the bleeding risk. The authors aimed to examine the association between aspirin use and bleeding during PKB. This systematic review and meta-analysis was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The article search was performed on MEDLINE and Scopus using queries specific to each database. Article inclusion was limited to primary studies. The meta-analysis compared the risk of major bleeding events between the aspirin-exposed versus nonexposed group. Pooled effect estimate was examined using random effects presented as odds ratio with 95% confidence intervals. Heterogeneity was assessed through Cochrane I 2 test statistics. Sensitivity and subgroup analyses were also performed according to kidney type. Ten studies were included in the review and four studies were included in the meta-analysis, reviewing a total of 34,067 PKBs. Definitions for significant aspirin exposure were inconsistent between studies, limiting comparisons. Studies with broader definitions for aspirin exposure mostly showed no correlation between aspirin use and postbiopsy bleeding. Studies with strict definitions for aspirin exposure found an increased risk of hemorrhagic events in the aspirin-exposed group. No significant differences were found between the aspirin-exposed and comparison groups regarding major bleeding events (odds ratio 1.72; 95% confidence interval 0.50 to 5.89, I 2 =84%). High-quality evidence on the effect of aspirin on the bleeding risk is limited. Our meta-analysis did not show a significantly increased risk of major bleeding complications in aspirin-exposed patients. Further studies are needed to define a more comprehensive approach for clinical practice.

Efficacy and safety of low-dose aspirin on preventing transplant renal artery stenosis: a prospective randomized controlled trial

BACKGROUND

Transplant renal artery stenosis (TRAS) is a vascular complication after kidney transplantation associated with poor outcomes. This study aimed to analyze the efficacy and safety of low-dose aspirin for preventing TRAS.

METHODS

After kidney transplantation, patients were enrolled from January 2018 to December 2020 in Henan Provincial People's Hospital. A total of 351 enrolled recipients were randomized to an aspirin group with low-dose intake of aspirin in addition to standard treatment ( n = 178), or a control group with only standard treatment ( n = 173). The patients was initially diagnosed as TRAS (id-TRAS) by Doppler ultrasound, and confirmed cases were diagnosed by DSA (c-TRAS).

RESULTS

In the aspirin and control groups, 15.7% (28/178) and 22.0% (38/173) of the recipients developed id-TRAS, respectively, with no statistical difference. However, for c-TRAS, the difference of incidence and cumulative incidence was statistically significant. The incidence of c-TRAS was lower in the aspirin group compared with the control group (2.8% [5/178] vs. 11.6% [20/173], P = 0.001). Kaplan-Meier estimates and Cox regression model identified the cumulative incidence and hazard ratio (HR) of TRAS over time in two groups, showing that recipients treated with aspirin had a significantly lower risk of c-TRAS than those who were not treated (log-rank P  = 0.001, HR = 0.23, 95% confidence interval [CI]: 0.09-0.62). The levels of platelet aggregation rate ( P  < 0.001), cholesterol ( P  = 0.028), and low-density lipoprotein cholesterol ( P  = 0.003) in the aspirin group were decreased compared with the control group in the third-month post-transplantation. For the incidence of adverse events, there was no statistical difference.

CONCLUSION

Clinical application of low-dose aspirin after renal transplant could prevent the development of TRAS with no significant increase in adverse effects.

TRIAL REGISTRATION

Clinicaltrials.gov, NCT04260828.

Thromboprophylaxis after kidney transplantation in children: Ten-year experience of a single Brazilian center

BACKGROUND

Kidney transplantation is the gold standard treatment for children with end-stage chronic kidney disease. Graft thrombosis is an important cause of graft failure, with high morbidity, mortality, and impact on quality of life and to the health system. The role of thromboprophylaxis in this setting is still uncertain. We describe the demographic characteristics and thrombotic risk factors in pediatric renal transplant recipients, determining the rate of renal graft thrombosis, and discuss the role of thromboprophylaxis.

METHODS

This retrospective study reviewed 96 pediatric renal transplantations between 2008 and 2017 in a single hospital. Patients were assigned to one of two groups: children who did not receive thromboprophylaxis after transplantation and those who did. We reported their characteristics, comparing the incidence of graft thrombosis and hemorrhagic complications between the groups.

RESULTS

Forty-nine patients (51%) received thromboprophylaxis. Thrombosis occurred in 5 patients who did not receive thromboprophylaxis (5.2%) compared with none in the group that did (p = .025). In all patients, renal graft thrombosis resulted in early graft loss. Thirteen patients had hemorrhagic complications. Seven were unrelated to pharmacological thromboprophylaxis (2 major, 1 moderate, and 4 minor bleeding, which either did not receive thromboprophylaxis or had bleeding prior to thromboprophylaxis), while six occurred during heparinization (2 major, 1 moderate, and 3 minor bleeding). There was no significant difference in the rate of hemorrhagic complications between the groups (p = .105).

CONCLUSIONS

The rate of renal graft thrombosis was 5.2%. Thrombosis remains an important cause of early graft loss. Thromboprophylaxis was associated with a reduction in graft thrombosis without increased risk of bleeding.

Prophylactic antithrombotic management in adult and pediatric kidney transplantation: A systematic review and meta-analysis

BACKGROUND

RGT is a major cause for early graft loss after KTx. Although evidence-based recommendations are lacking, aP is often used to prevent RGT. This systematic review aimed to determine the effectiveness and safety of aP in adult and pediatric KTx recipients.

METHODS

MEDLINE, EMBASE, Cochrane Controlled Trials Register, conference proceedings, and electronic databases for trial registries were searched for eligible studies using search terms relevant to this review (April 21, 2020). The systematic review was carried out following the recommendations of the Cochrane Collaboration and the Prefered Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Statement.

RESULTS

Twelve studies comprising 2370 patients (adult = 1415, pediatric = 955) were included, of which three were RCTs. The overall risk for developing RGT was lower in the group with aP compared with the control group (RR 0.24, 95% confidence interval 0.12-0.49). The antithrombotic drugs used were heparin (7/12), acetylsalicylic acid (2/12), a combination of both (2/12), and dipyridamole (1/12) with a high variability in timing, dosing, and mode of application. Adverse effects were reported rarely, with minor bleeding as the main complication. The non-randomized studies had significant risks of bias in the domains of patient selection, confounder, and measurement of outcomes.

CONCLUSION

Based on pooled analysis, aP seems to reduce the risk of RGT in KTx. However, the reliability of these results is limited, as the quality of the available studies is poor and information on adverse effects associated with aP is scarce. Additional high-quality research is urgently needed to provide sufficient data supporting the use of aP in KTx.

Current practice of antithrombotic prophylaxis in pediatric kidney transplantation-Results of an international survey on behalf of the European Society for Paediatric Nephrology

BACKGROUND

Renal graft thrombosis (RGT) is one of the main causes for early graft loss in pediatric kidney transplantation (KTx). Despite the lack of evidence-based recommendations, antithrombotic prophylaxis (aP) is used to prevent RGT.

METHODS

An online survey supported by the European Society for Pediatric Nephrology was developed to investigate the current practice of aP in pediatric KTx recipients <18 years.

RESULTS

A total of 80 pediatric KTx centers from 37 countries participated in the survey. Antithrombotic prophylaxis was performed in 96% of the pediatric renal transplant centers (all/selected patients: 54%/42%). The main overall used drugs were as follows: low-molecular-weight heparin (89%), unfractionated heparin (UFH) (69%), and acetylsalicylic acid (ASS) (55%). Ten different aP management strategies were identified as follows: 51% used a single drug and 48% combined two drugs sequentially. The corresponding centers started aP predominantly within 24 hours after pediatric KTx; 51% preferred UFH for starting aP. In centers switching to a second drug (51%), this change was performed after 10 ± 6 days; of these 57% preferred ASS for maintenance aP. Reported median aP duration was 51 days (range 1-360).

CONCLUSIONS

Despite the use of aP in almost all responding pediatric KTx centers, there is no uniform management strategy. Notwithstanding, UFH seems to be the preferred drug for the early post-operative period of pediatric KTx, and ASS for maintenance prophylaxis following pediatric KTx. Prospective studies are needed to further evaluate the benefits and risks of aP, preferably resulting in guidelines for the management in pediatric KTx.

Pros and Cons of Aspirin Prophylaxis for Prevention of Cardiovascular Events in Kidney Transplantation and Review of Evidence

Kidney transplant recipients have traditional and nontraditional risk factors which can lead to coronary artery disease and sudden death with a functional graft loss. Aspirin has been used traditionally for prevention of cardiovascular and cerebrovascular accidents. It has beneficial effects in secondary prevention of cardiovascular events in general population. Its use for primary prophylaxis is still disputed. Bleeding and theoretical risk of nephrotoxicity are the major concerns about its use. The data on aspirin in kidney transplant population is sparse. This review will focus on various pros and cons of aspirin use for prevention of cardiovascular events in kidney transplant recipients and a way forward.

Sticky Platelet Syndrome: An Unrecognized Cause of Acute Thrombosis and Graft Loss

Introduction

Sticky platelet syndrome (SPS) is a prothrombotic disease that is not well recognized and difficult to diagnose.

Case Report

We present a case of a 49-year-old diabetic woman on ambulatory peritoneal dialysis therapy who underwent a kidney transplant from living-related donor. The donor was her sister with whom she shared one haplotype and absence of donor specific antibodies. The posttransplant evolution was torpid, developing progressive deterioration, which made us suspect a failure in the graft. Doppler ultrasound reported renal vein thrombosis and hypoperfusion of the renal artery. Without clinical improvement, she required a reintervention that ended in graftectomy, in which the histopathological report showed negative C4d with medullary and cortical infarction. Hematological studies were negative for antibodies against phospholipids, with correct levels of proteins C and S and antithrombin. Platelet aggregometry studies were carried out, which were compatible with SPS.

Conclusions

Recognition of SPS in pretransplant studies is difficult if there is no history of previous thrombotic events. However, we must consider this entity in cases of acute thrombosis and loss of the graft of uncertain origin.

The effect of aspirin on kidney allograft outcomes; a short review to current studies

CONTEXT

The use of aspirin in chronic kidney disease (CKD) patients has been shown to reduce myocardial infarction but may increase major bleeding. However, its effects in kidney transplant recipients are unclear.

EVIDENCE ACQUISITIONS

A literature search was performed using MEDLINE, EMBASE, and Cochrane Database of Systematic Reviews from inception through September 2016. We included studies that reported odd ratios, relative risks or hazard ratios comparing outcomes of aspirin use in kidney transplant recipients. Pooled risk ratios (RR) and 95% confidence interval (CI) were assessed using a random-effect, generic inverse variance method.

RESULTS

We included 9 studies; enrolling 19759 kidney transplant recipients that compared aspirin with no treatment. Compared to no treatment, aspirin reduced the risk of allograft failure (4 studies; RR: 0.57, 95% CI: 0.33 to 0.99), allograft thrombosis (2 studies; RR: 0.11, 95% CI: 0.02 to 0.53), and major adverse cardiac events (MACEs) or mortality (2 studies; RR: 0.72, 95% CI: 0.59 to 0.88), but not allograft rejection (3 studies; RR: 0.86, 95% CI: 0.45 to 1.65) or delayed graft function (DGF) (2 studies; RR: 1.00, 95% CI: 0.58 to 1.72) in kidney transplant recipients. The data on risk of major or minor bleeding were limited.

CONCLUSIONS

Our meta-analysis demonstrates that administration of aspirin in kidney transplant recipients is associated with reduced risks of allograft failure, allograft thrombosis, and MACEs or mortality, but not allograft rejection or DGF. Future studies are needed to assess the risk of bleeding, and ultimately weigh the overall risks and benefits of aspirin use in specific kidney transplant patient populations.

Effect of Long-Term, Low-Dose Aspirin Therapy on Renal Graft Function

OBJECTIVES

Despite improvements in immunosuppressive protocols for renal transplant, long-term success of renal transplant is still limited by the occurrence of interstitial fibrosis and tubular atrophy. Some studies have shown that aspirin decreases the severity of kidney ischemia-reperfusion injury and the development of tubular atrophy in animal models. This study aimed to assess the effects of aspirin therapy started at the time of transplant on long-term graft function.

MATERIALS AND METHODS

We compared renal graft function of 82 patients on low-dose aspirin 75 mg once daily who underwent renal transplant between 1 January 2000 and 31 December 2010 from a single center with 65 patients not taking aspirin. For each patient, the following measurements were collected: age, sex, creatinine level, type of donor, cold ischemia time, occurrence of acute allograft rejections, number of HLA mismatches, first transplant, intake of statins, number of antihypertensive medications, and number of days posttransplant. Patients were excluded from the study who were on aspirin before transplant or who had coronary artery disease.

RESULTS

Multilevel modelling was used to compare renal allograft function, as measured by serum creatinine levels, between patients taking and not taking aspirin after kidney transplant. Aspirin was not significantly associated with creatinine levels (P = .59) after adjusting for other relevant variables.

CONCLUSIONS

Low-dose aspirin started at the time of transplant has a negligible effect on renal allograft function over the 15-year study period posttransplant.

Chronic Allograft Nephropathy: Pathogenesis and Management of an Important Posttransplant Complication

Chronic allograft nephropathy is a devastating complication of kidney transplantation that is responsible for a significant proportion of graft loss. This complication is characterized by a progressive decline in kidney function, which is not attributable to a specific cause. Many risk factors exist for the development of chronic allograft nephropathy, including donor-, recipient-, and transplant-related factors (eg, use of calcineurin inhibitors and acute rejection episodes), as well as comorbid conditions such as hypertension and hyperlipidemia. There is no definitive treatment for this complication; management has focused on minimization or withdrawal of calcineurin inhibitors in conjunction with addition of sirolimus or mycophenolate mofetil. Alterations in the immunosuppressive regimen must be done cautiously, as precipitating acute rejection will cause further damage to the allograft. Optimal control of blood pressure, particularly with the use of agents such as angiotensin II receptor blockers, in conjunction with management of dyslipidemia may be effective concurrent therapies in patients with chronic allograft nephropathy.

Hypercoagulability in Kidney Transplant Recipients

Thrombosis remains an important complication after kidney transplantation. Outcomes for graft and deep vein thrombosis are not favorable. The majority of early kidney transplant failure in adults is due to allograft thrombosis. Risk stratification, early diagnosis, and appropriate intervention are critical to the management of thrombotic complications of transplant. In patients with end-stage renal disease, the prevalence of acquired risk factors for thrombosis is significantly high. Because of hereditary and acquired risk factors, renal transplant recipients manifest features of a chronic prothrombotic state. Identification of hereditary thrombotic risk factors before transplantation may be a useful tool for selecting appropriate candidates for thrombosis prophylaxis immediately after transplantation. Short-term anticoagulation may be appropriate for all patients after kidney transplantation.

Identification of risk factors for vascular thrombosis may reduce early renal graft loss: a review of recent literature

Renal graft survival has improved over the past years, mainly owing to better immunosuppression. Vascular thrombosis, though rare, therefore accounts for up to one third of early graft loss. We assess current literature on transplantation, identify thrombosis risk factors, and discuss means of avoiding thrombotic events and saving thrombosed grafts. The incidence of arterial thrombosis was reported to 0.2–7.5% and venous thrombosis 0.1–8.2%, with the highest incidence among children and infants, and the lowest in living donor reports. The most significant risk factors for developing thrombosis were donor-age below 6 or above 60 years, or recipient-age below 5-6 years, per- or postoperative hemodynamic instability, peritoneal dialysis, diabetic nephropathy, a history of thrombosis, deceased donor, or >24 hours cold ischemia. Multiple arteries were not a risk factor, and a right kidney graft was most often reported not to be. Given the thrombosed kidney graft is diagnosed in time, salvage is possible by urgent reoperation and thrombectomy. Despite meticulous attentions to reduce thrombotic risk factors, thrombosis cannot be entirely prevented and means to an early detection of this complication is desirable in order to save the kidneys through prompt reoperation. Microdialysis may be a new tool for this.

Accumulation of pro-cancer cytokines in the plasma fraction of stored packed red cells

INTRODUCTION

Perioperative blood transfusion has been linked to decreased survival in pancreatic cancer; however, the exact causal mechanism has not been elucidated. Allogeneic transfusions are known to expose patients to foreign cells and lipid mediators. We hypothesize that stored packed red cells (pRBCs) contain pro-cancer cytokines that augment tumor progression. We analyzed the plasma fraction of stored pRBCs for pro-cancer cytokines and evaluated the affect of both storage time and leukocyte reduction on these mediators.

METHODS

Chemiarray™ analysis for pro-cancer cytokines was performed on the acellular plasma fraction of stored leukocyte-reduced (LR) and non-leukocyte-reduced (NLR) pRBCs at day 1 (D.1-fresh) and day 42 (D.42-outdate) of storage. Elevated expression of monocyte chemotactic protein-1 (MCP-1), regulated on activation, normal T cell expressed and secreted (RANTES), angiogenin, tumor necrosis factor-alpha (TNF-α), epidermal growth factor (EGF), and platelet-derived growth factor (PDGF) was found. Specific enzyme-linked immunosorbent assay was performed for each of these factors in LR and NLR blood at D.1, day 28, and D.42. Data were analyzed by ANOVA. A p value ≤ 0.05 was considered significant; N ≥ 4 per group. Migration assays were performed using inhibitors of EGF (gefitinib) and PDGF (imatinib) on murine pancreatic adenocarcinoma cells (Pan02) exposed to D.1 and D.42 LR and NLR plasma. Proliferation assays were performed on Pan02 cells to test the inhibition of PDGF.

RESULTS

MCP-1 levels increased with storage time in LR blood, 86.3 ± 6.3 pg/ml at D.1 vs. 121.2 ± 6.1 pg/ml at D.42 (p = 0.007), and NLR blood, 78.2 ± 7.3 pg/ml at D.1 vs. 647.8 ± 220.7 pg/ml at D.42 (p = 0.02). RANTES levels are lower in LR compared to NLR stored blood, 3.0 ± 1.9 vs. 15.8 ± 0.7 pg/ml at D.42 (p < 0.001), but similar in D.1 blood, 13.8 ± 1.8 pg/ml in LR vs. 12.0 ± 1.6 pg/ml in NLR. Angiogenin levels were different between LR and NLR blood, 0 pg/ml (undetectable) vs. 44.2 ± 3.7 pg/ml (p < 0.001). Storage time did not affect concentration. TNF-α levels were not different between LR and NLR blood, and there was no storage time effect on concentration. EGF and PDGF levels increased with storage time in NLR blood only, 216.4 ± 3.8 pg/ml at D.1 vs. 1,436.4 ± 238.6 pg/ml at D.42 for EGF (p = 0.001), and 61.6 ± 6.0 pg/ml at D.1 vs. 76.5 ± 1.7 pg/ml at D.42 (p = 0.003) for PDGF. Inhibition of EGF reduced migration in Pan02 cells treated with D.42 NLR blood, 245.9 ± 11.2 vs. 164.6 ± 10.6 cells/hpf (p < 0.001). Inhibition of PDGF had no effect on Pan02 migration and reduced cell proliferation in cells treated with D.42 NLR, 181.1 ± 1.5% over control vs. 157.5 ± 2.1% (p < 0.001).

CONCLUSION

Pro-cancer cytokines that can augment tumor progression were identified in pRBCs. Some of these factors are present in fresh blood. The soluble factors identified herein may represent possible therapeutic targets to offset negative effects of transfusion. These data stress the need for efforts in cancer patients to reduce transfusion requirements if needed.

Preventing AVF thrombosis: the rationale and design of the Omega-3 fatty acids (Fish Oils) and Aspirin in Vascular access OUtcomes in REnal Disease (FAVOURED) study

Background

Haemodialysis (HD) is critically dependent on the availability of adequate access to the systemic circulation, ideally via a native arteriovenous fistula (AVF). The Primary failure rate of an AVF ranges between 20–54%, due to thrombosis or failure of maturation. There remains limited evidence for the use of anti-platelet agents and uncertainty as to choice of agent(s) for the prevention of AVF thrombosis. We present the study protocol for a randomised, double-blind, placebo-controlled, clinical trial examining whether the use of the anti-platelet agents, aspirin and omega-3 fatty acids, either alone or in combination, will effectively reduce the risk of early thrombosis in de novo AVF.

Methods/Design

The study population is adult patients with stage IV or V chronic kidney disease (CKD) currently on HD or where HD is planned to start within 6 months in whom a planned upper or lower arm AVF is to be the primary HD access. Using a factorial-design trial, patients will be randomised to aspirin or matching placebo, and also to omega-3 fatty acids or matching placebo, resulting in four treatment groups (aspirin placebo/omega-3 fatty acid placebo, aspirin/omega-3 fatty acid placebo, aspirin placebo/omega-3 fatty acid, aspirin/omega-3 fatty acid). Randomisation will be achieved using a dynamic balancing method over the two stratification factors of study site and upper versus lower arm AVF. The medication will be commenced pre-operatively and continued for 3 months post surgery. The primary outcome is patency of the AVF at three months after randomisation. Secondary outcome measures will include functional patency at six and twelve months, primary patency time, secondary (assisted) patency time, and adverse events, particularly bleeding.

Discussion

This multicentre Australian and New Zealand study has been designed to determine whether the outcome of surgery to create de novo AVF can be improved by the use of aspirin and/or omega-3 fatty acids. Recently a placebo-controlled trial has shown that clopidogrel is effective in safely preventing primary AVF thrombosis, but ineffective at increasing functional patency. Our study presents significant differences in the anti-platelet agents used, the study design, and surgical and patient demographics that should contribute further evidence regarding the efficacy of anti-platelet agents.

Trial Registration

Australia & New Zealand Clinical Trials Register (ACTRN12607000569404).

Platelets influence vascularized organ transplants from start to finish

This review relates the basic functions of platelets to specific aspects of organ allograft rejection. Platelet activation can occur in the donor or recipient before transplantation as well as during antibody- and cell-mediated rejection. Biopsies taken during organ procurement from cadaver donors have documented that activated platelets are attached to vascular endothelial cells or leukocytes. In addition, many patients waiting for transplants have activated platelets due to the diseases that lead to organ failure or as a result of interventions used to support patients before and during transplantation. The contribution of platelets to hyperacute rejection of both allografts and xenografts is well recognized. Intravascular aggregates of platelets can also be prominent in experimental and clinical transplants that undergo acute antibody or cell-mediated rejection. In acute rejection, platelets can recruit mononuclear cells by secretion of chemokines. After contact, monocytes, macrophages and T cells interact with platelets through receptor/ligand pairs, including P-selectin/PSGL-1 and CD40/CD154. There is a potential for therapy to inhibit platelet mediated immune stimulation, but it is counterbalanced by the need to maintain coagulation in the perioperative period.

Outcome after kidney transplantation in children with thrombotic risk factors

BACKGROUND

According to the data from the North American Pediatric Renal Transplant Cooperative Study (NAPRTCS), vascular thrombosis accounts for 11.6% of graft losses in pediatric renal transplantation. In adults, inherited and acquired thrombophilic risk factors, e.g. factor V Leiden mutation, have been associated with early graft loss and increased rejection episodes. Data on the impact of these factors on the outcome of children after renal transplantation are rare.

METHODS/PATIENTS

Sixty-six pediatric patients awaiting renal transplantation (mean age 10.1 yr) were screened for inherited and acquired risk factors for hypercoagulable disorders (protein C, S, and antithrombin III deficiency, antiphospholipid antibodies, factor V Leiden, prothrombin, and MTHFR mutation) in order to intensify anticoagulation in those with an increased risk for thrombophilia: intravenous heparin was administered with a partial prothrombin time (PTT) prolongation of 50 s for 14 days and switched to low-molecular-weight heparin for another 8 wk before aspirin was introduced for the first year. Patients without hypercoagulable risk factors were treated with heparin without PTT prolongation for 14 days and switched to aspirin immediately afterwards. The results on graft survival, incidence of acute rejection episodes, and long-term renal graft function were analyzed between recipients with and without hypercoagulable risk factors.

RESULTS

Thrombophilic risk factors were identified in 27.3% of our patients. No thrombosis occurred. One serious bleeding complication led to a second surgical intervention. The rate of acute rejection episodes was not increased in patients with and without thrombotic risk factors after 90 days (16.7 vs. 25%), 1 yr (22.2 vs. 33.3%), and 3 yr (38.9 vs. 41.7%) of follow-up, respectively (p = n.s.). After a mean follow-up of 3 yr the kidney function was comparable in both groups, with 63.1 in recipients with and 69.8 mL/min/1.73 m(2) in recipients without hypercoagulable risk (p = n.s.). At latest follow-up, three graft losses were found not to be attributed to thrombotic risk factors.

INTERPRETATION

Children with thrombophilic risk factors were identified and treated with an intensified anticoagulation regimen after renal transplantation. An increased risk for graft failure, acute rejection episodes, or impaired renal function for pediatric renal transplant recipients with hypercoagulable status was not found.

Successful renal transplantation in a patient with heterozygous prothrombin gene, factor V Leiden mutation and heparin-induced thrombocytopenia using r-hirudin as anticoagulant

Vascular complications remain the most common cause of early renal allograft loss in patients with end-stage renal failure. Underlying thrombophilic disorders increase the risk of early graft thrombosis. A male adolescent with high-risk thrombophilia because of combined heterozygous factor V Leiden (G1691A) and prothrombin gene (G20210A) mutation developed HIT II. Hemodialysis and subsequent renal transplantation were undertaken using recombinant hirudin, a direct and selective thrombin inhibitor, as an anticoagulant. Primary function in the transplanted kidney was excellent. No thrombotic or hemorrhagic events have occurred and follow-up showed excellent long-term graft survival. Patients on HD have an increased risk for the development of HIT, and therefore, they need repetitive screening for the development of acquired thrombotic risk factors (e.g. HIT II or lupus anticoagulant). R-hirudin is efficacious and safe on both HD and following renal transplantation.

LOW-DOSE ASPIRIN THERAPY IS ASSOCIATED WITH IMPROVED ALLOGRAFT FUNCTION AND PROLONGED ALLOGRAFT SURVIVAL AFTER KIDNEY TRANSPLANTATION

BACKGROUND

Aspirin treatment has an undoubted beneficial impact on the progression of cardiovascular diseases. We hypothesized that aspirin also protects allograft function and survival in the context of chronic renal allograft dysfunction, which displays decisive pathophysiologic features that are similar to those involved in atherogenesis.

METHODS

A retrospective, multivariate analysis was performed to assess the effect of low-dose aspirin treatment (100 mg/day) on allograft function and survival of 830 renal transplant recipients. Allograft function was evaluated by serum creatinine levels, urine protein levels, and the presence of hematuria.

RESULTS

Median allograft survival time was significantly longer in patients receiving low-dose aspirin therapy compared with patients receiving no aspirin treatment (n=205, 13.8 +/- 2.6 vs. 7.8 +/- 0.3 years, n=625; adjusted relative risk=0.443, 95% confidence interval [0.323-0.608], P<0.0001). Statin treatment and a recent time point of transplantation, reflecting the qualitative advances of the applied immunosuppressive therapy, were further positive determinants of renal allograft survival. The number of antihypertensive agents, representing the extent of hypertension, was a negative determinant of allograft survival. Transplant function was better preserved in aspirin-treated patients, who displayed a slower increase of serum creatinine and less proteinuria and hematuria during the observation period. The duration of aspirin treatment was positively associated with better allograft function.

CONCLUSIONS

Low-dose aspirin therapy substantially improves renal allograft function and allograft survival. These findings suggest that aspirin should be considered to complement long-term posttransplant medical treatment regimens.

The effect of heparin on graft thrombosis in pediatric renal allografts

Graft thrombosis is an important cause of early (<4 weeks) renal graft loss. Reports show that heparin reduces the incidence of early renal allograft thrombosis. Routine peri-operative administration of unfractionated heparin was introduced in our unit in 1994. We conducted a retrospective study of 254 transplants, undertaken in children, between 1987 and 2000. There were 126 children who did not receive heparin (group 1) and 128 who did (group 2). Recipient characteristics and immunosuppression were similar in both groups. The incidence of graft loss secondary to thrombosis was compared between the groups. Variables previously identified with increased risk of graft loss, including donor age, recipient age, cold ischaemia time (CIT), multiple donor vessels, surgical complications, and side of graft donation, were examined using logistic regression. Thrombosis occurred in 14 grafts in group 1 and 11 grafts in group 2 (odds ratio 0.7, 95% confidence interval 0.3-1.6, P=not significant). The mean time to graft loss was similar in groups 1 and 2 (6.6, SD 3.9, range 2-12 days and 7.9, SD 4.4, range 1-14 days, respectively) ( P=0.445). Young recipient age ( P=0.006), young donor age ( P=0.009), increasing CIT ( P=0.007), and surgical complications ( P=0.002) increased the risk of graft thrombosis. A reduction in the incidence of early renal allograft thrombosis upon introduction of heparin was not demonstrated.

Hypercoagulability in renal transplant recipients. Identifying patients at risk of renal allograft thrombosis and evaluating strategies for prevention

Renal transplantation improves survival and quality of life for patients with end-stage renal disease (ESRD). Improvements in immunosuppressive therapy have reduced early allograft loss due to acute rejection to very low levels. Early allograft loss, due to acute thrombotic complications, remains a constant and proportionally increasing complication of renal transplantation. Identifying risk factor(s) for thrombosis amenable to preventive strategies has been elusive. Epidemiological studies have attempted to define risk in terms of modifiable (drugs, dialysis modality, surgical procedure) and non-modifiable (age, diabetes mellitus, vascular anomalies) factors, or identify changes in coagulation or fibrinolysis promoting a more thrombotic state. Most recently the evolution of thrombophilia research has established the potential for inherited hypercoagulability to predispose to acute allograft thrombosis. Inheritance of the factor V Leiden (FVL), prothrombin G20210A mutation, or the presence of antiphospholipid antibodies (APA) may increase the risk of renal allograft thrombosis approximately 3-fold in selected patients. Patients with ESRD due to systemic lupus erythematosus (SLE) appear at particularly high risk of thrombosis, especially if they have either APA or detectable beta(2)-glycoprotein-1. Data for other hypercoagulable states such as hyperhomocystinemia or the C677T polymorphism of the methylenetetrahydrofolate reductase gene are deficient. Patients with APA, FVL, or prothrombin G20210A mutation also appear to have greater graft loss due to vascular rejection, possibly reflecting immunological injury upon the vascular wall exacerbated or induced by the prothrombotic state. While substantial in vitro data suggest cyclosporine is prothrombotic, an independent clinical association with allograft thrombosis is unproven. Interventions to reduce thrombotic risk including heparin, warfarin, and aspirin have been evaluated in both selected high-risk groups (heparin and warfarin) and unselected populations (heparin and aspirin). In unselected patients at low clinical risk, aspirin (75-150 mg/day) with or without a short period of unfractionated heparin (5000U twice a day for 5 days) appears to reduce the risk of renal allograft thrombosis significantly with a low risk of bleeding, especially when compared with low molecular weight heparins which risk accumulation in renal failure. In high-risk groups (identified thrombophilic risk factor, previous thrombosis, or SLE) longer period of heparin, with or without aspirin and maintenance with warfarin, should be considered. Re-transplantation following graft loss due to vascular thrombosis can be undertaken with a low risk of recurrence. Further prospective studies evaluating both putative risk factors and intervention strategies are required to determine whether routine clinical screening for thrombophilic factors is justified.