Excellent outcome in infants and small children with thrombophilias undergoing kidney transplantation

Surgical considerations in paediatric kidney transplantation: an update

Background

Kidney transplantation has established itself as the most appropriate mode of renal replacement therapy for the majority with end-stage kidney disease. Although at present this is applicable for children as well as adults, a few decades back kidney transplantation was not considered a first-line option in children. This was due to inferior outcomes following transplantation in this age group compared to that of adults. These poor results were attributed to challenges in paediatric transplantation such as the shortage of suitable donors, technical difficulties in performing a sound vascular anastomosis and the adverse effects of immunosuppressive medication on growth and development. However, current patient and graft-centred outcomes after paediatric transplantation equal or surpass that of adults. The advances in evaluation and management of specific surgical concerns in children who undergo transplantation, such as pre-transplant native nephrectomy, correction of congenital anomalies of the urinary tract, placement of an adult-sized kidney in a small child and minimizing the risk of allograft thrombosis, have contributed immensely for these remarkable outcomes.

Conclusions

In this review, we aim to discuss surgical factors that can be considered unique for children undergoing kidney transplantation. We believe that an updated knowledge on these issues will be invaluable for transplant clinicians, who are dealing with paediatric kidney transplantation.

INHERITED PROTEIN C AND PROTEIN S DEFICIENCY IN RENAL TRANSPLANT CANDIDATES OF SINDH PROVINCE, PAKISTAN

Background: Thrombophilia is a common risk factor for venous thromboembolism. The objective of this study was to determine prevalence of inherited protein C and protein S deficiency in renal transplant candidates of Sindh Province, Pakistan. Material & Methods: This cross-sectional study was conducted in Department of Pathology, Sindh Institute of Urology and Transplantation, Karachi, Pakistan from 16-10-2010 to 15-4-2011. 300 renal transplant candidates were selected. Candidates with acquired thrombotic disorders, women taking oral contraceptives and patients taking anti-coagulants during previous one week were excluded. Venous blood samples were collected before starting dialysis procedure or at least two days after last dialysis session. Platelet-poor plasma (PPP) was parted using plastic pipettes and protein C and protein S were processed on coagulation analyzer. Sex, age groups (<40 and ≥ 40years), presence of protein C deficiency and presence of protein S deficiency were nominal variables and analyzed by count and percentage along with population parameters. Results: 300 renal transplant candidates included 199 (66.33%) men and 101 (33.67%) women and 238 (79.33%) in age group <40 years and 62 (20.67%) cases in age group ≥40 years. Prevalence of protein C deficiency was 6.66% (20/300) and of protein S deficiency was 4% (12/300). Prevalence of PC deficiency was higher in men 5.33% than women 1.33%. Also prevalence of PS deficiency was higher in men 3.0% than women 1.0%. Prevalence of PC deficiency was higher in age group <40 years 5.67% than ≥40 years 1.0%. Also prevalence of PS deficiency was higher in age group <40 years 3.33% than ≥40 years 0.66%. Conclusion: More prolonged and follow-up studies are needed to define the true significance of deficiency of protein C and S (coagulation inhibitors) in post-transplant settings.

Assessment of prophylactic heparin infusion as a safe preventative measure for thrombotic complications in pediatric kidney transplant recipients weighing <20 kg

Small-sized kidney recipients (<20 kg) are at high risk of allograft vessel thrombosis. HP has been used to mitigate this risk but may infer an increase in bleeding risks. Therefore, we aim to determine whether HP is a safe means to prevent thrombosis in small kidney transplant patients by comparing those who have received HP and those who have NHP. A retrospective review of patients < 20 kg who underwent kidney transplant in our institution from 2000 to 2015 was performed. At our institution, unfractionated heparin 10 units/kg/hour is used as HP since 2009. Patients at increased risk of thrombosis (previous thrombosis, thrombophilia, nephrotic syndrome) and bleeding (therapeutic doses of heparin, diagnosis of coagulopathy) were excluded. Fifty-six patients were identified (HP n = 46; NHP n = 10). Baseline demographics were similar between HP and NHP. There was no statistical difference in frequency of transfusions, surgical re-exploration, or thrombotic events between HP and NHP. The HP group was more likely to have drop in Hb > 20 g/L (67.4% vs 30.0%, P = 0.038), and those who had drop in Hb > 20 g/L were more likely to also require pRBC transfusions (63.0% vs 20.0%, P = 0.017). Within the HP group, those who had bleeding complications had similar Hb levels as those who did not at baseline and post-transplant. Outcomes in the HP and NHP groups were no different with respect to thrombosis or significant bleeding complications requiring pRBC transfusions or surgical intervention. Future prospective studies are required to investigate the balance of preventing thrombosis and risks of pRBC transfusions for small-sized kidney recipients.

Utility of thrombophilia screening in pediatric renal transplant recipients

Thrombosis after kidney transplantation may result in catastrophic outcomes, including graft loss. Thrombophilia has been implicated in post-transplant thrombosis; data, however, are inconclusive on the impact of acquired and inherited thrombophilia and resultant thrombosis in renal graft recipients. We aimed to evaluate whether identifying children with thrombophilia during the pretransplant evaluation predicted post-transplant outcomes. We reviewed 100 kidney transplants performed in 100 children, aged 1-18 years, in a single-center retrospective study. Routine pretransplant comprehensive thrombophilia evaluation was completed. Thrombophilia was demonstrated in 36% patients (N = 36). TEs occurred in 11 patients before kidney transplant. Low PS and antithrombin were found in 9/86 (10.5%) and 2/89 (2.2%) children, respectively. Heterozygosity for FLV and PGM were found in 5/81 (6.2%) and 1/93(1.1%) children, respectively. A post-transplant thrombotic event occurred in 10 children (10%); six involved the renal transplant. The association between a history of a pretransplant thrombotic event and post-operative renal graft thrombosis approached, but did not reach significance (P = 0.071). There was no association between preoperative screening abnormalities and post-operative TEs. Graft loss due to a thrombotic event occurred in two patients; none had underlying thrombophilia. Our data suggest that the utility of universal, comprehensive preoperative thrombophilia testing is not beneficial in determining risk of post-operative graft thrombosis. Thrombophilia testing may be considered in a select population with a history of pretransplant thrombotic event.

Vascular thrombosis in pediatric kidney transplantation: Graft survival is possible with adequate management

OBJECTIVE

Vascular thrombosis (VT) in pediatric kidney transplantation (KT) is a dreaded event that leads to graft loss in almost 100% of cases. In recent years, VT has become the most common cause of early graft loss. The aim of this study was to analyze our experience in diagnosis and treatment of VT and the impact of a new management protocol on patient outcome.

METHODS

We conducted a retrospective study of 176 consecutive KT performed at our institution by the pediatric urology team between January 2000 and December 2015 and identified patients with VT. A protocol of prevention and early detection of VT was introduced in 2012.

RESULTS

Out of 176 KT, nine cases of VT were identified (5.1%). The mean recipient age was 5.1 years (SD 4.9 years) and mean weight was 22.28 kg (SD 15.6 kg). Diagnosis was intraoperative in two cases and within the first 24 h after surgery in the remaining seven. Immediate surgical exploration was performed after diagnosis in all. Of the five episodes that occurred before 2012, all developed complete graft ischemia requiring transplantectomy. However, in the four cases diagnosed after 2012, graft perfusion could be restored in three, and abdominal wall closure with a mesh and delayed sequentially closure under ultrasound guidance was performed. With a follow-up of 30, 25, and 20 months, the three recovered grafts are still functioning normally.

CONCLUSIONS

Increased awareness and the application of a protocol for prevention, detection and treatment of VT in pediatric KT can prevent graft loss. Immediate surgical intervention is mandatory after diagnosis. Avoiding compartment syndrome with delayed sequential closure may be useful to improve graft survival.

Renal transplantation experience in a patient with factor V Leiden homozygous, MTHFR C677T heterozygous, and PAI heterozygous mutation

Vascular complications are important causes of allograft loss in renal transplantation. A two and a half-month-old boy was diagnosed with posterior urethral valve and progressed to end-stage renal disease at eight yr of age. During the HD period, a central venous catheter was replaced three times for repeated thrombosis. The boy was found to be homozygous for FVL and heterozygous for both MTHFR (C677T) and PAI. At the age of 12, renal transplantation was performed from a deceased donor. Postoperative anticoagulation therapy was initiated with continuous intravenous administration of heparin at the dose of 10 IU/kg/h. HD was performed for the first three days. By the fourth day of transplantation, his urine output had increased gradually. Heparin infusion was continued for 18 days during hospitalization at the same dosage. Thereafter, he was discharged with LMWH. On the third month after transplantation, his serum creatinine level was 1.1 mg/dL and eGFR was 75.7 mL/min/1.73 m(2). He has still been using LMWH, and his eGFR was 78.7 mL/min/1.73 m(2) eight months after transplantation. Postoperative low-dose heparin treatment is a safe strategy for managing a patient with multiple thrombotic risk factors.

Successful Living-Related Renal Allograft in a Recipient With Factor V Leiden Deficiency: A Case Report

Thrombophilia due to activated protein C resistance (Leiden mutation) is the most common inherited thrombophilic disorder with 5% incidence in whites. Renal transplant of these patients entails a risk of vascular thrombosis soon after the transplant; and acute rejection episodes and graft loss within the first year. We present a case of a successful living-related renal transplant in man with a recent history of repeat episodes of vascular access thrombosis attributed to inherited thrombophilia (heterozygosity for factor V mutation Q506 and homozygosity for mutation T677 for methylene-tetrahydrofolate reductase). Transplant recipient was administered anticoagulation therapy with low molecular weight heparin pre- and postoperatively. No thrombotic or hemorrhagic events occurred posttransplant. A high suspicion of thrombophilic disorders in patients with end-stage renal disease with vascular access thrombotic events should be screened further to prevent failure of a subsequent renal transplant. Inherited thrombophilic disorders may not exclude living-related kidney transplant provided that anticoagulation therapy is admin-istered perioperatively.

Pediatric transplantation: preventing thrombosis

Due to progressive advances in surgical techniques, immunosuppressive therapies, and supportive care, outcomes from both solid organ transplantation and hematopoietic stem cell transplantation continue to improve. Thrombosis remains a challenging management issue in this context, with implications for both graft survival and long-term quality of life. Unfortunately, there remains a general paucity of pediatric-specific data regarding thrombosis incidence, risk stratification, and the safety or efficacy of preventative strategies with which to guide treatment algorithms. This review summarizes the available evidence and rationale underlying the spectrum of current practices aimed at preventing thrombosis in the transplant recipient, with a particular focus on risk factors, pathophysiology, and described antithrombotic regimens.

Kidney transplantation in children weighing less than 15 kg: extraperitoneal surgical access-experience with 62 cases

Small children are a challenging group in whom to perform KT. This retrospective study analyzed the results of 62 KTs in children weighing <15 kg, performed between 1998 and 2010, using extraperitoneal access and anastomosis of the renal vessels of donors to the aorta and IVC or iliac vessels of the recipients. Thirty-two (51.6%) grafts were LRDTs and 30 (48.4%) were DDRTs-28 of them pediatric. The mean age at KT was 3.7 ± 2.2 yr (1-12), and the mean weight was 12.3 ± 2.1 kg (5.6-14.9). Ten children weighed <10 kg, and five (8.1%) children presented previous thrombosis of the venous system. At one and five yr, patient survival was 93.2% and 84.2%, and graft survival was 85.2% and 72.7%. There were no differences between the rates for LRDT and DDRT. There were six vascular complications (four vascular thromboses, one laceration, and one renal artery stenosis) and two perirenal collections. Extraperitoneal access is a valid KT technique in children weighing <15 kg.

Kidney transplantation in infants and small children

Transplantation is now the preferred treatment for children with end-stage kidney disease. But not all pediatric age groups have enjoyed the same success. The number of transplants in infants and young children has lagged behind the number in older children. One reason for this is the philosophy of some centers to maintain infants on dialysis until they reach some arbitrarily determined age, at which time they would undergo a transplant. If kidney transplantation is the therapy of choice for older children with renal failure, and equivalent results can be obtained in all age groups, why should it not be offered to these youngest patients? Our center's philosophy for many years has been not to restrict transplant based on size or age. We have performed over 50 kidney transplants in infant recipients, and have shown equivalent results to those obtained in older children. Important factors in obtaining a successful outcome include the use of adult kidneys from a living donor, careful attention to operative and perioperative care, and performing the transplant early or in a preemptive fashion. The latter allows for minimizing the negative impact of uremia on physical and neurologic development in infants.

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.