Biomedical subjects

S R Alexander

Publications and source records attributed to S R Alexander.

At least 19 recordsLinked to original sources

PubMed2005

Hemofiltration for cytokine-driven illnesses: the mediator delivery hypothesis.

Hemofiltration is evolving as an adjunctive therapy for sepsis and other forms of systemic inflammation. Designed as a substitute for lost renal function, it is sometimes employed prior to the onset of renal failure to facilitate the nonspecific clearance of pro-inflammatory mediators. Prevailing theories suggest that hemofiltration attenuates the immune response when a threshold amount of excess cytokine is removed at the semi-permeable membrane. In this article we introduce an alternative hypothesis, in which hemofiltration exerts its effect by reinvigorating lymphatic flow and function. Crystalloid "replacement" solution, as much as 48 to 72 liters daily, is infused to restore intravascular volume lost through production of ultrafiltrate. Partial redistribution into interstitium and lymph mobilizes inflammatory mediators and other proteins, cellular byproducts, excessive ground matrix, fragments of apoptotic cells and free DNA. These substances are then metabolized, scavenged or cleared at multiple sites, including the reticuloendothelial system, liver, kidney, erythrocyte, and hemofilter.

Body Water↗

PubMed2004

The Prospective Pediatric Continuous Renal Replacement Therapy (ppCRRT) Registry: design, development and data assessed.

Many issues plague the pediatric ARF outcome literature, which include data only from single center sources, a relative lack of prospective study, mixture within studies of renal replacement therapy modality without stratification and inconsistent use of methods to control for patient illness severity in outcome analysis. Since January 2001, the Prospective Pediatric CRRT (ppCRRT) Registry Group has been collecting data from multiple United States pediatric centers to obtain demographic data regarding pediatric patients who receive CRRT, assess the effect of different CRRT prescriptions on circuit function and evaluate the impact of clinical variables on patient outcome. The aim of the current paper is to describe the ppCRRT Registry design, review the decision process and rationale for the options chosen for the ppCRRT format and discuss the analysis plan and future projects envisioned for the ppCRRT Registry.

Acute Kidney Injury↗

PubMed2001

Recurrence of hemolytic uremic syndrome after renal transplantation in children: a report of the North American Pediatric Renal Transplant Cooperative Study.

BACKGROUND: Hemolytic uremic syndrome (HUS) is the cause of renal failure in 2-4% of children on dialysis. After renal transplantation, HUS can recur, but recurrence rate and risk factors are controversial. METHODS: We reviewed the recurrence of HUS within the North American Pediatric Renal Transplant Cooperative Study (NAPRTCS) registry and used a separate questionnaire to ascertain additional clinical information. RESULTS: Of 68 renal allografts, HUS recurred in 6 allografts (8.8%) occurring in five patients (8.2%). Four patients had atypical HUS, whereas one patient had classic HUS. HUS recurred after transplantation in 33 days or less in all but one allograft. Outcome was poor with five of six allografts lost, despite treatment with fresh-frozen plasma or plasmapheresis. Cyclosporine had no effect on outcome or HUS recurrence. CONCLUSIONS: The risk of HUS recurrence in the allograft is 8-9% and is heightened in atypical HUS. Treatment was not effective and graft outcome was poor. Cyclosporine does not affect HUS recurrence.

Adolescent↗

PubMed2001

The cytoplasmic domain of L-selectin participates in regulating L-selectin endoproteolysis.

Neutrophil recruitment at sites of inflammation is regulated by a series of adhesion and activation events. L-selectin (CD62L) is a leukocyte expressed adhesion protein that is important for neutrophil accumulation and rolling along the vascular endothelium. L-selectin is unique from other adhesion molecules involved in leukocyte transmigration in that its adhesiveness appears to be regulated partly by rapid endoproteolysis. Cleavage of L-selectin occurs within a membrane-proximal region that results in ectodomain shedding and retention of a 6-kDa transmembrane fragment. The cleavage domain of L-selectin has been well characterized through mutational analysis. Whether the cytoplasmic domain of L-selectin also plays a role in regulating shedding is controversial. We have previously shown that the Ca(2+)-sensing protein calmodulin (CaM) constitutively associates with the cytoplasmic domain of L-selectin in transfected cell lines. However, in the absence of mapping and mutational analysis of the CaM-binding region of L-selectin, there remains no direct evidence that this interaction affects shedding. Using synthesized peptides and expressed L-selectin constructs, we demonstrate that CaM binding activity occurs in the membrane-proximal region of the cytoplasmic domain. Mutations engineered in this region that prevent CaM binding increase the proteolytic turnover of L-selectin. Moreover, we demonstrate that CaM binding to the 6-kDa transmembrane fragment is greatly reduced compared with intact L-selectin in neutrophils, suggesting that CaM binding is regulated. These data imply that the cytoplasmic domain of L-selectin can regulate shedding by a mechanism in which bound CaM may operate as a negative effector.

Amino Acid Sequence↗

PubMed2001

Long-term plasmapheresis and protein A column treatment of recurrent FSGS.

Transient or intermittent plasmapheresis with concurrent immunosuppressive therapy is thought to be beneficial in the treatment of recurrent focal segmental glomerulosclerosis (FSGS) in the early post-transplant period. The results of long-term (6-year) plasmapheresis therapy, in a 9-year-old female with an immediate recurrence of FSGS [urinary protein/urinary creatinine (UP/UC)=17.7] after cadaveric renal transplant, are presented. A 4-week plasmapheresis course induced a decline in the proteinuria, but a relapse occurred after cessation of plasmapheresis. Addition of protein A column therapy led to a further decrease in the proteinuria, to a non-nephrotic range. Long-term control of the nephrotic syndrome was established using a chronic treatment regimen consisting of a single-volume plasmapheresis, followed by a protein A column treatment, performed on sequential days every 3-4 weeks. Mean UP/UC values decreased to 1.15+/-0.9. A course of cyclophosphamide was successfully used to control a worsening of proteinuria 4 years post transplant. Although sequential renal biopsies demonstrated progressive glomerular sclerosis, the patient's mean calculated creatinine clearance only modestly declined from 78.3 ml/min per 1.73 m2, at the time of transplantation, to 62.7 ml/min per 1.73 m2, 6 years later. This patient demonstrated dependence on plasmapheresis/protein A column therapy to maintain a clinical remission of her FSGS recurrence. While long-term plasmapheresis and protein A column therapy in combination with immunosuppressive therapy reversed the effects of uncontrolled nephrosis and possibly facilitated long-term renal allograft survival, the glomerular sclerosis continued to progress.

Child↗

PubMed2001

Loss of living donor renal allograft survival advantage in children with focal segmental glomerulosclerosis.

BACKGROUND: Because of concerns of increased risk of graft loss with recurrent disease, living donor (LD) transplantation in children with focal segmental glomerulosclerosis (FSGS) has been controversial. METHODS: The North American Pediatric Renal Transplant Cooperative Study (NAPRTCS) database from January 1987 to January 2000 was examined to determine differences in demographics, treatment, and outcomes in children with FSGS compared with other renal diseases. RESULTS: Data on 6484 children, 752 (11.6%) with FSGS, demonstrated that FSGS patients were more likely to be older and black, and were less likely to receive either pre-emptive or LD transplant (P < 0.001). No differences existed in human lymphocyte antigen (HLA) matching or immunosuppression regimens. Acute tubular necrosis occurred in more FSGS patients following LD (11.8 vs. 4.6%) or cadaveric (CD; 27.9 vs. 16.3%) transplants (P < 0.001). Graft survival was worse for LD FSGS patients (5 years 69%) compared with no FSGS (82%, P < 0.001) and was not significantly different than CD graft survival in the FSGS (60%) and No FSGS groups (67%). The LD to CD ratios of relative risk of graft failure were higher in FSGS patients (test for interaction, P = 0.01). Recurrence of original disease was the only cause of graft failure that differed between groups (P < 0.001). A greater percentage of LD FSGS graft failures was attributed to recurrence (P = 0.06). CONCLUSIONS: The impact of FSGS on graft survival in children is greatest in LD transplants, resulting in loss of expected LD graft survival advantage. The rationale for LD grafts in children with FSGS should be based on factors other than better outcomes typically associated with LD transplantation.

Child↗

PubMed2001

Pulse methylprednisolone, cyclosporine, and ace inhibitor therapy decreases proteinuria in two siblings with familial focal segmental glomerulosclerosis.

Familial focal segmental glomerulosclerosis (FSGS) is a heterogeneous renal disease characterized by proteinuria and an unremitting deterioration of renal excretory function. Previous studies showed corticosteroid unresponsiveness and a variable response to cyclophosphamide therapy. We hypothesized that treatment with pulse methylprednisolone therapy (PMT), alternate-day corticosteroids, and cyclosphosphamide or cyclosporine would decrease proteinuria in patients with familial FSGS. Two adolescent brothers, 13 and 16 years old, presented with nephrotic range proteinuria, but with normal renal excretory function. Both brothers had renal biopsies that showed FSGS with mesangial hypercellularity and tubular atrophy. Intravenous PMT, at doses of 1 g, was initiated per the Tune-Mendoza protocol. Both patients received lisinopril therapy. One brother (case 1) was treated with PMT, alternate-day corticosteroids, and cyclophosphamide (total cumulative cyclophosphamide dose was 154.3 mg/kg). Urinary protein-to-urinary creatinine (UP/UC) ratios decreased from 6.79 to 3.79. Cyclosporine therapy decreased the UP/UC further from 2.48 to 0.76 at the end of PMT. The other brother (case 2), treated with PMT, alternate-day corticosteroids, and cyclosporine, experienced a decrease in UP/UC from 7.27 to 1.14. At the time of last evaluation, approximately 7 months after the last PMT dose, the UP/UC ratios were 0.27 (case 1) and 0.37 (case 2). PMT-attributable adverse effects were not severe. Both patients continued to receive oral cyclosporine and lisinopril after completion of PMT. PMT and cyclosporine therapy may reduce proteinuria, without decreasing renal excretory function, in some patients with familial FSGS. Further evaluation of cyclosporine therapy and PMT of patients with familial FSGS is warranted.

Adolescent↗

PubMed2001

The clinical efficacy of higher hematocrit levels in children with chronic renal insufficiency and those undergoing dialysis.

The optimal hematocrit target range in children with end-stage renal disease, who are receiving recombinant human erythropoietin, is ambiguous due to the lack of compelling, age-appropriate studies. There are a large number of adult and pediatric studies which show that physical performance as well as morbidity and mortality are positively influenced by partial normalization of the hematocrit to 30 vol% to 36 vol%. Cognition studies performed in adults similarly show improvement with partial correction of hematocrit. Normalization of hematocrit studies show lower mortality rates, incremental further improvement in cognition, and greater resolution of cardiac anomalies when compared with patients with partial correction of anemia. Conversely, cardiac death rates may increase in adult patients receiving hemodialysis with preexisting cardiac disease, and there are concerns about the effect of recombinant human erythropoietin on catheter/shunt/fistula patency and on blood pressure. The high cost of recombinant human erythropoietin and established Medicare and Dialysis Outcomes Quality Initiative target hematocrit ranges have also influenced pediatric nephrologists in their assessment of the risk-benefit ratios, despite new adult data suggesting that maintenance of higher hematocrits may be cost-effective. The rationale of using adult-derived hematocrits in children with end-stage renal disease needs to be re-examined in the context of the unique growth and developmental requirements of children. A prospective, multicenter study which determines the relative benefits and risks of age-adjusted hematocrit normalization in children with renal failure is warranted.

Anemia↗

PubMed2001

Radiology goes filmless.

PROBLEM: Long turnaround time for radiology reports, unacceptable percentage of misplaced films. SOLUTION: Installation of hospitalwide PACS, implementation of voice recognition dictation system, upgrade of RIS. RESULTS: Rapid and significant improvement in reporting times, virtual elimination of misplaced films, integration of radiology services throughout the enterprise. KEYS TO SUCCESS: Detailed financial model and needs assessment, commitment by management and staff, well-planned implementation, choice of vendor that provides total solution and support.

Cost Savings↗

PubMed2000

Effects of selective protein kinase C inhibitors on the proteolytic down-regulation of L-selectin from chemoattractant-activated neutrophils.

The signaling factors that direct the rapid shedding of L-selectin from neutrophils upon chemoattractant stimulation are poorly understood. Protein kinase C (PKC) has been implicated, yet previous studies have relied on the use of phorbol esters and nonselective kinase inhibitors. We treated neutrophils with various selective kinase inhibitors to evaluate their effects on N-formyl-methionyl-leucyl-phenylalanine (fMLP)-induced L-selectin shedding. We found that three selective inhibitors of PKC, structurally related to staurosporine, largely blocked both fMLP- and phorbol 12-myristate 13-acetate (PMA)-induced L-selectin shedding; however, these inhibitors did not affect fMLP-induced up-regulation of Mac-1 (CD11b/CD18) expression, which has been shown not to involve PKC. Other selective serine, threonine, and tyrosine kinase inhibitors were found not to block fMLP-induced L-selectin shedding. These findings provide more definitive evidence for the role of PKC in chemoattractant-induced L-selectin proteolysis. It is interesting that certain highly selective PKC inhibitors, not structurally related to staurosporine, were found to directly induce L-selectin shedding from neutrophils.

Acetophenones↗

PubMed2000

Sodium ferric gluconate therapy in renal transplant and renal failure patients.

Intravenous infusion of sodium ferric gluconate (Ferrlecit) has been reported to be effective and safe in pediatric and adult hemodialysis patients with iron depletion. We sought to expand on the previous studies by treating 13 consecutive pediatric renal failure and renal transplant patients with sodium ferric gluconate doses that were higher than previously reported. Efficacy was defined as: (1) an increase in hematocrit of > or = 3 vol% with no change or a decrease in erythropoietin dose or (2) a stable hematocrit with a decrease of > or = 25% in the erythropoietin, 2 weeks to 2 months after sodium ferric gluconate infusion. Two dosing strategies were employed: (1) high dose, where single dose sodium ferric gluconate (mg) approximately calculated iron deficit, and (2) sodium ferric gluconate, 62.5 mg/dose for children < 40 kg, 125 mg/dose for children > 40 kg, infused on eight consecutive hemodialysis runs. There was only one self-limited adverse reaction in 60 doses. Three patients with previous adverse reactions to iron dextran tolerated sodium ferric gluconate without adverse effect. Sodium ferric gluconate was efficacious in eight out of ten patients that received a cumulative dose > 5 mg/kg. The mean hematocrit increased 30.3 +/- 7.8 to 36.4 +/- 4.4 vol% (P = 0.04) and the mean erythropoietin dose decreased 251.5 +/- 149.1 to 100.7 +/- 113.0 units/kg/week (P = 0.02). Although sodium ferric gluconate appears to be effective and safe at the doses used, multicenter, prospective pharmacokinetic and clinical trials of sodium ferric gluconate should be conducted in children.

Adolescent↗

PubMed1999

Chronic dialysis in children and adolescents. The 1996 annual report of the North American Pediatric Renal Transplant Cooperative Study.

The 1996 annual report of the North American Pediatric Renal Transplant Cooperative Study (NAPRTCS) summarizes data submitted from 130 centers on 2,208 patients in whom 2,787 independent courses of dialysis were performed between 1 January 1992 and 16 January 1996. Approximately two-thirds of the dialysis population were maintained on peritoneal dialysis (PD), with automated PD remaining the preferred modality. There were 964 episodes of peritonitis in 1,018 patient years, yielding an overall peritonitis rate of 1 episode every 13 patient months. More PD patients attended school full time than hemodialysis (HD) patients at baseline (77% vs. 45%), which continued at 6, 12, and 24 months of followup. There were fewer Hispanic patients who were full-time students, whether on HD or PD, compared with white or black patients; 18% of Hispanic patients did not attend school, even though they were medically capable. The majority of dialysis courses terminated due to transplantation (54%), with change in dialysis modality the next most-common reason (28%). Early dialysis termination for any reason was seen more often in HD than PD (40% vs. 23% at 6 months), but by 24 months similar percentages of PD and HD courses had been terminated (75% HD, 72% PD). The most-common PD access was a Tenckhoff catheter with a single cuff, a straight tunnel and lateral exit site. The majority of HD accesses were external percutaneous catheters, with the sublcavian vein the most-common site. Erythropoietin was administered in 93% of HD and PD patients at 24 months.

Adolescent↗

PubMed1999

Optimal care of the pediatric end-stage renal disease patient on dialysis.

This manuscript is an effort on behalf of the American Society of Pediatric Nephrology to provide recommendations designed to optimize the clinical care of pediatric patients with end-stage renal disease (ESRD). Although many of the recommendations are evidenced-based with the supporting data being derived from a variety of sources, including patient registries, others are opinion-based and derived from the combined clinical experience of the authors. In all cases, it is recommended that the decision to initiate dialysis should be made only after an assessment of a combination of biochemical and clinical characteristics. Irrespective of the choice of dialysis modality (hemodialysis v peritoneal dialysis), dialysis efficacy should be measured regularly, and the dialysis prescription should be designed to achieve target clearances. Attention to dialysis adequacy, control of osteodystrophy, nutrition, and correction of anemia is mandatory, because all may influence patient outcome in terms of growth, cognitive development, and school performance. Finally, the availability of a multidisciplinary team of pediatric specialists is desirable to provide all facets of pediatric ESRD care, including renal transplantation, in an optimal manner. Future clinical research efforts intended to address topics such as dialysis adequacy, anemia management, and growth should be encouraged.

Adaptation, Psychological↗

PubMed1999

Predictive factors for delayed graft function (DGF) and its impact on renal graft survival in children: a report of the North American Pediatric Renal Transplant Cooperative Study (NAPRTCS).

We define delayed graft function (DGF) as the need for dialysis during the first post-transplant week. We analyzed 5272 transplants, of which 2486 were of living donor (LD) and 2786 were of cadaver donor (CD) origin. Twelve per cent (620/5272) of all patients developed DGF. Donor specific rates were 5.6% for LD and 19.1% for CD patients. Factors predictive of DGF in CD patients were: African-American race (25%), prolonged cold ischemia (24%), absence of T-cell induction antibody therapy and absence of HLA-DR matching. The relative risk (RR) for graft failure due to DGF was 6.02 (p < 0.001) in LD patients and 2.58 (p < 0.001) for CD recipients. Two-year graft survival (GS) in LD patients without DGF was 89.6%, compared to 41.6% for those with DGF (p < 0.001); in CD patients it was 80.2% and 49.5%, respectively (p < 0.001). Censoring for primary non-function, GS for LD patients with a functioning graft at 30 d post-transplant and no DGF was 91.5%, compared to 70.1% for those with DGF (p < 0.001); GS for CD patients was 83.8% and 68.7%, respectively (p < 0.001). However, when patients whose grafts had failed during the first year were censored no differences in GS were noted between patients with and without DGF for either LD or CD recipients. To determine whether DGF acts as an independent risk factor for graft failure, patients were segregated into four groups: rejection with DGF; rejection without DGF; DGF without rejection; and no DGF, no rejection. When these groups were compared DGF emerged as an independent risk factor for graft failure. This large study reviewing pediatric renal transplantation over 10 yr clearly delineates the role of DGF as a major risk factor for graft failure.

Adolescent↗

PubMed1999

Steady improvement in short-term graft survival of pediatric renal transplants: the NAPRTCS experience.

This report of pediatric renal transplantation covers the years 1987-1998. Since its inception in 1987, the NAPRTCS has collected data on 6,038 transplants performed in 5,516 patients provided by 73 renal centers across the country. FSGS, together with developmental lesions of dysplasia and obstructive uropathy, account for 40% of all transplants. There has been a steady increase in the use of LD donors among children with 54% of all transplants in 1996 and 1997 being live-related. About 72% of LD transplants are performed in Caucasian children, with African-American children unfortunately receiving a disproportionate percentage of CD kidneys. There has been a steady decline in the use of CD kidneys recovered from young individuals and a gradual decline in the number of transplants performed in young recipients (< 6 years old). Graft survival for LD recipients was 91%, 84% and 79% at one, 3 and 5 years, respectively, and the comparative figures for CD recipients were 81%, 72% and 64%, respectively. Acute and chronic rejections account for most of the graft losses, with chronic rejection accounting for more than 30%. There has been a steady improvement in one-year graft survival of CD recipients with the 1997-1998 cohort exhibiting an improvement of 16% over the 1987-1988 cohort. This improvement has been brought about by eliminating the use of infant donor kidneys, reducing the number of random transfusions and increasing the maintenance dose of cyclosporine. Posttransplant growth continues to be poor, with catch-up growth being exhibited only in children under age 6.

Adolescent↗

PubMed1998

Pediatric renal transplantation: indications and special considerations. A position paper from the Pediatric Committee of the American Society of Transplant Physicians.

Renal transplantation of children with chronic renal insufficiency (CRI) and end-stage renal disease (ESRD) appears to be the optimal form of renal replacement therapy. This report, which expresses the opinions of the nephrology members of the Pediatric Committee of the American Society of Transplant Physicians, discusses the indications for pediatric renal transplantation and identifies the unique aspects of caring for children with CRI and ESRD. Indications for pediatric renal transplantation include: 1) symptoms of uremia not responsive to standard therapy; 2) failure to thrive due to limitations in total caloric intake; 3) delayed psychomotor development; 4) hypervolemia; 5) hyperkalemia; and 6) metabolic bone disease due to renal osteodystrophy. The urgency and timing of renal transplantation in children must be considered in the context of a number of issues unique to children with CRI and ESRD such as delayed cognitive and educational performance, growth retardation, delayed puberty, etiology of ESRD, and timing of immunizations. In addition, these children frequently display various inherited and sporadic syndromes with multiorgan involvement requiring the expertise of a variety of pediatric subspecialists including the pediatric urologist, who plays a critical role in the evaluation of children with obstructive uropathy and other anomalies of the genito-urinary system. The advantages of a living-related donor are also delineated. The importance of adequate immunosuppression on graft function, early recognition of the signs and symptoms acute rejection, preventive strategies for minimizing the morbidity and mortality from viral infections in the post-transplant period, and the impact of transplantation on cognitive function, educational status, and catch-up growth are also discussed. To address these complex issues, transplant care of pediatric patients must be provided by a multidisciplinary team of pediatric health care professionals.

Child↗

PubMed1998

Pediatric Transplant Grand Rounds. Pediatric kidney transplantation at Stanford.

(1) We believe that we have achieved excellent graft survival with pediatric kidney transplantation because: (a) we have had no technical losses; (b) there have been no primary immunologic losses within 4 years following transplantation; (c) we have avoided ATN. (2) Our cyclosporine dosage has been greater than the average dosage reported by the NAPRTCS, and we believe that this has led to: (a) a low incidence of rejection episodes; (b) because of this, good 1 and 2 year average serum creatinine levels. (3) In the management of adult-sized kidneys in infants and small children I have discussed: (a) the rationale and strategy to prevent vascular thrombosis, ATN and primary non-function; (b) the importance of optimizing intravascular volume, as well as renal and aortic blood flow. (4) With regard to the management of congenital urologic abnormalities I have discussed: (a) the strategy to avoid unnecessary surgery and to avoid scar around the aorta and the vena cava, particularly in infants and small children; (b) my philosophy regarding the abnormal bladder and the successful use of the small defunctionalized urinary bladder. We believe that these have been the primary ingredients to the success we have seen. I also harken back and continue to practice the adage advanced by my former mentor Dr. Fred Belzer that 'no kidney is better than a bad kidney!' And this could not be more true than in pediatric kidney transplantation, where graft failure enhanced by suboptimal graft quality may potentially both cripple the child and shorten his/her life.

Adult↗

PubMed1998

The impact of donor source, recipient age, pre-operative immunotherapy and induction therapy on early and late acute rejections in children: a report of the North American Pediatric Renal Transplant Cooperative Study (NAPRTCS).

Acute rejection is a frequent event in pediatric transplantation. In addition to graft loss, acute rejection episodes stimulate the development of chronic rejection and inhibit growth in children post-transplantation. In this study, we analyzed our data from 1987 through 1996 to identify acute rejection episodes in children. In 2,520 living donor (LD) transplants there were 2,540 rejection episodes (rejection ratio: 1.1), and in 2,579 cadaver donor (CD) transplants 3,653 episodes were observed (rejection ratio: 1.32). For LD recipients the first rejection occurred sooner when there was at least one HLA-DR mismatch (RR=1.6, p<0.001) and prophylactic T-cell antibody was not used (RR=1.4, p<0.001). For CD transplants absence of prophylactic T-cell antibody (RR=1.2, p<0.001) and donor age below five years were risk factors (RR=1.5, p<0.001). Late initial acute rejections were seen in 327 of 1,471 patients (22.2%) who were rejection free at one year. At risk for the development of late rejections were children over the age of six years at transplantation (RR=1.7, p<0.001) and children of non-white origin (RR=1.5, p <0.002). For LD transplant recipients in the age range of 0-5 years, irreversible rejection was observed in 8.7% compared to 4.1% for older children (RR=1.46, p<0.001). Similar results for CD transplants were 12.6% versus 6.6% (RR=1.5, p<0.00). The high frequency of rejection episodes in children and the greater irreversibility in younger children suggest pediatric patients may have a more robust immune response. Current ongoing studies in the molecular mechanisms of the pathogenesis of rejection in surveillance biopsies of children may help determine if this hypothesis is valid.

Acute Disease↗