Routine transplant Doppler ultrasonography following pediatric kidney transplant.

The utility and cost-effectiveness of routine transplant renal DU as a screening test in the immediate postoperative period following pediatric renal transplantation has not been systematically evaluated. Our center's transplant protocol includes a routine DU on postoperative day 3, unless an earlier DU was obtained for a specific indication. We retrospectively evaluated 113 consecutive pediatric renal transplant recipients. Indication for DU (routine vs. non-routine), timing, results, and graft outcome data were collected. We determined whether the DU result affected patient management. Eighty routine DU examinations were evaluated. Thirty (37.5%) of the 80 routine DUs had abnormalities. Most abnormalities were minor and did not require intervention. One patient with a dysfunctional bladder had mild hydronephrosis; this led to a decision to increase the frequency of bladder catheterization. This was the only intervention based upon the routine DUs. Twenty percent of routine DUs revealed abnormalities that led to a follow-up study, but none of these studies led to an intervention. The incremental cost of each DU exceeded $1080 and the incremental cost-effectiveness ratio for a documented change in management exceeded $86, 400. Our results suggest that routine post-transplant DU is not cost-effective in pediatric renal allograft recipients.

Linear growth in pediatric renal transplant recipients receiving sirolimus.

SRL is a potent macrolide immunosuppressive agent that can be used as maintenance therapy for prevention of rejection and avoidance of CNI nephrotoxicity. However, animal studies indicate that SRL may inhibit skeletal and muscle growth. We analyzed linear growth in 25 children, age 1-15 yr old, maintained on SRL to determine whether SRL is detrimental to linear growth. Height z-scores at baseline were compared with those at 24 months. We also compared linear growth in children receiving SRL to patients maintained on TAC. Height z-scores over 24 months did not significantly change in the SRL group as a whole. Z-scores improved in 13 of 25 patients (52%). Children with improved z-scores were significantly younger than patents who did not display improved growth: 6 ± 5 yr vs. 11 ± 4 yr (p < 0.05). Height z-scores in SRL and TAC-based patients were no different initially and at 24 months, and a similar number of patients in each group displayed improved height scores. Height z-scores improved in 52% of patients on SRL and occurred predominantly in younger patients for the initial 24 months of treatment. Linear growth in SRL patients was also similar to the results in TAC-based patients. Therefore, our data did not identify a significant adverse effect of SRL on growth.

Five-year experience using sirolimus-based, calcineurin inhibitor-free immunosuppression in pediatric renal transplantation.

From December 2003 to December 2008, we employed a protocol for withdrawing TAC and converting to SRL in a cohort of low-risk renal pediatric transplant recipients. We report our experience in these children with respect to graft survival, AR episodes, renal function, and adverse events. All patients received basiliximab induction and TAC, MMF, and prednisone. Criteria for conversion to SRL included first transplants without histologic evidence for AR on three-month surveillance biopsies. Patient exclusion criteria included AR prior to or before surveillance biopsies, polyoma (BK) virus nephropathy, a history of nephrotic syndrome, or multiple organ transplants. Fifty-one of 137 patients who received transplants from December 2003 to December 2008 met criteria for withdrawal of TAC and were converted to SRL. SRL was discontinued in 11 children because of adverse events within 12 months after conversion. Among the remaining 40 patients, actuarial graft survival was 91% at five yr. AR occurred in 13% of patients within one yr after conversion. Complications from SRL included aphthous ulcers (30%); viremia with BK virus (20%), EBV (13%), and CMV (3%); proteinuria (7%); elevated cholesterol (7%); diabetes mellitus (2%); thrombocytopenia (2%); erectile dysfunction (2%); and lymph edema (2%). SRL was discontinued in 20%, predominantly for aphthous ulcers. Our experience with SRL-based immunosuppression demonstrates that a CNI-free regimen can be successful in lower-risk patients meeting our selection criteria. Aphthous ulcers and BK virus viremia were the most prevalent adverse events.

24 weeks of valganciclovir prophylaxis in children after renal transplantation: a 4-year experience.

BACKGROUND: Cytomegalovirus (CMV) is the most common opportunistic infection after solid-organ transplant. Valganciclovir prophylaxis significantly reduces disease, but limited data are available on its use in children. Recently, an increase in delayed-onset CMV disease has been noted with some arguing that longer prophylaxis may decrease late-onset disease. METHODS: Single-center, retrospective analysis of pediatric renal transplant patients receiving 24 weeks valganciclovir prophylaxis (15 mg/kg/day, maximum 900 mg/day) from January 2004 to December 2008, aiming to measure the incidence of CMV disease and toxicity of valganciclovir. RESULTS: We enrolled 111 patients, 60% males, 46% African Americans, and median age at transplant 14.5 years (range 1.4-20.4 years). Sixty-nine percent of donors and 44% of recipients were seropositive pretransplant. Median duration of valganciclovir use was 5.9 months (range 0.5-24 months). CMV viremia and disease occurred in 27% and 4.5%, respectively. All patients with disease presented after prophylaxis ended and all were D+/R-. Thymoglobulin use (P = 0.04) and positive donor CMV status (P = 0.02) were associated with a higher risk of CMV viremia. Twenty-four percent had hematologic toxicity directly associated with valganciclovir. CONCLUSIONS: Valganciclovir use in children was effective as prophylaxis against CMV disease; no children at our institution developed disease while on therapy. Our regimen of 24 weeks of prophylaxis was associated with a lower rate of late-onset disease than previous reports with 12-week regimens. Further controlled studies should be considered to compare longer versus shorter periods of prophylaxis and dose reductions and their impact on prevention of late-onset disease, resistance, cost, and toxicity.

BK virus nephropathy: a pediatric nephrologist's perspective.

Polyomavirus (BK)-associated nephropathy (BKVN) is now recognized as significant problem in pediatric renal transplants that may lead to progressive allograft dysfunction. BKVN was first recognized in 1999 in adult renal transplant recipients, and most data have been obtained from this patient population. Today, there is an increasing number of publications pertaining to children with BKVN that allows for a selective analysis of the pediatric population. Most early pediatric publications were predominantly cases reports. However, several retrospective and prospective studies are now available that provide important insights with respect to the incidence of BKVN in the pediatric transplant population, the efficacy of treatment strategies, and the risk factors for developing BKVN. This review analyzes several of the most significant studies that address these issues.

Pretransplant IgG antibodies to polyoma BK virus in pediatric renal transplants.

We retrospectively measured IgG antibody levels to BKV in pretransplant sera and compared levels in children who developed BK viremia to a control group who remained free of infection after transplantation. Sera from 45 renal transplant patients were available for analysis (BK viremia = 23, controls = 22). Serum BKV PCR levels ranged from 3400 to 6.5 million DNA copies/mL (mean +/- s.d.: 978K +/- 1.77 million) and were highest in patients with BK nephritis (p = 0.007). Overall, 35% of children with BK viremia were BKV-seronegative vs. 9% of children in control group (p = 0.04), but mean antibody levels were similar between viremic and control patients (p = 0.15). However, children who developed viremia later than six months post-transplantation had significantly lower antibody levels compared with controls (p = 0.004) and patients with early viremia (p = 0.007), and may represent de novo infection or reinfection, rather than recurrence of latent infection. Pretransplant antibody status was significantly associated with subsequent development of BK viremia. Although our findings identified possible factors for developing BK viremia, there was sufficient overlap of both seropositive status and antibody levels among viremic patients and the control group to question the clinical utility of pretransplant IgG antibodies.

Prevalence of clinical rejection after surveillance biopsies in pediatric renal transplants: does early subclinical rejection predispose to subsequent rejection episodes?

We analyzed rates of both SCR and CR in children receiving SB at three months post-transplant to determine if SCR predisposed patients to acute CR. Acute rejection was defined according to Banff criteria to include borderline classification or higher. All cases of SCR and CR were treated with anti-rejection protocols. Between October 2004 and July 2008, 89 SB were performed at three months post-transplant. Twenty-six cases of SCR were detected (29%). Sixteen patients experienced 22 episodes of biopsy-proven CR occurring after SB, including seven episodes following SCR and 15 after normal SB. The onset of CR varied from one to 27 months after SB and occurred at similar intervals for cases with SCR and normal SB. The percentage of patients remaining free of CR at 30 months post-transplant was similar in patients with SCR and normal SB. Renal function and graft survival at 30 months also were no different between patients with SCR and those with normal SB. Early-SCR, when treated with rejection protocols, is not a prognostic indicator for subsequent CR episodes.

Tacrolimus withdrawal and conversion to sirolimus at three months post-pediatric renal transplantation.

UNLABELLED: Nephrotoxicity caused by CNI may adversely affect long-term graft outcomes. For this reason, we have adopted a protocol for withdrawing TAC and converting to SRL at three months post-renal transplantation. All recipients received basiliximab induction and TAC, MMF, and prednisone. Patients without acute rejection by surveillance biopsy at three months were eligible for SRL conversion. RESULTS: From August 2004 to September 2006, TAC was withdrawn and replaced by SRL in 30 first transplant recipients, who were followed for six to 39 months (mean 18 +/- 8). Renal function did not improve significantly after SRL conversion (p = 0.25). Acute rejection occurred in three patients (10%) at five to 12 months after CNI withdrawal. There were no occurrences of wound healing problems, pneumonitis or post-transplant lymphoproliferative disease. Thrombocytopenia and diabetes each occurred in one patient. Four patients received treatment for hypercholesterolemia. CNI withdrawal and replacement with SRL was an effective regimen in children who did not display biopsy evidence of acute rejection at three months post-transplant. While these early results are promising, the ultimate benefit of this protocol to enhance the long-term renal function and graft survival requires ongoing follow-up.

Surveillance renal transplant biopsies and subclinical rejection at three months post-transplant in pediatric recipients.

UNLABELLED: Subclinical acute rejection (SCR) has been increasingly recognized in adult renal transplant recipients with the advent of surveillance biopsies. However, in children, surveillance biopsies are not routinely performed at most centers. Therefore, the incidence, predisposing factors, treatment, and clinical outcomes of SCR remain unclear in children. From August 2004 to December 2005, we performed 36 protocol biopsies at three months post-transplantation. All patients had received induction therapy with basiliximab and were maintained on prednisone, MMF, and tacrolimus. Sixteen cases of SCR were detected by biopsy (44%). Age, gender, race, donor source, or serum creatinine did not discriminate between children with SCR and those with normal biopsies. All cases of SCR were treated with high doses of methylprednisolone. At one yr post-transplant, renal function was similar in children with SCR to those with normal surveillance biopsies (p = 0.62). Because of the high incidence of SCR, the maintenance dose of MMF was increased by 50% in 20 children transplanted after December 2005. This resulted in a significant decline in the incidence of SCR from 44 to 15% (p < 0.05). However, the incidence of polyomavirus (BK) viremia also increased significantly in these children (p < 0.005). CONCLUSION: A high incidence of SCR was found on surveillance biopsies at three months post-transplant and could not be predicted by age, gender, race, donor source, or serum creatinine. The occurrence of SCR declined significantly by increasing the dose of MMF, but resulted in an increase in BK viremia. We conclude that surveillance biopsies provide valuable information in the management of pediatric renal transplant recipients. Increasing immunosuppression to avoid SCR should be weighed against the risk for infection.

Polyomavirus (BK) in pediatric renal transplants: evaluation of viremic patients with and without BK associated nephritis.

Polyoma BK virus (BKV) is emerging as a significant complication in renal transplantation, which may lead to renal dysfunction and graft loss caused by BK nephritis (BKN). We report the management and outcome of 20 children who developed BK viremia. Serum polymerase chain reaction (PCR) for BKV DNA was measured monthly for the first year in transplant recipients and every six months thereafter, or for unexplained creatinine elevation. With seroconversion to +PCR, patients were managed with reduction of immunosuppression. Renal biopsy was performed if PCR or creatinine did not improve. From June 2003 to January 2006, 20 children seroconverted for BKV at 23 to 1410 days post-transplant (mean 467 days). Sixteen underwent renal biopsy. Eight displayed BKN, three acute rejection and five were normal. Patients with BKN displayed higher PCR and serum creatinine and presented later than children with viremia without BKN. There were no differences between the two groups for age, gender, donor source or immunosuppression. Seven children with BKN received treatment with cidofovir. Thirteen patients (65%) remained PCR+ after reduction of immunosuppression or treatment with cidofovir. Renal function was stable in 16 children (80%) at 13 +/- 6 months after seroconversion. Four patients with BKN demonstrated progressive loss of renal function. BKV infection in children can occur as an early complication or may develop years after transplantation. Patients with BKN presented later and displayed higher viral loads and serum creatinine than viremic patients without BKN. Children with BKN remained PCR+ despite reduction of immunosuppression or treatment with cidofovir and were at greater risk for loss of renal function.

Sirolimus in pediatric patients: results in the first 6 months post-renal transplant.

We report our experience with sirolimus in children during the first 6 months after renal transplantation. From July 2000 to January 2004, 66 children received 33 deceased donor and 33 living donor transplants. Maintenance immunosuppression included sirolimus 3 mg/m(2) in addition to prednisone and tacrolimus or cyclosporine. Patient survival was 100% and graft survival was 65 of 66. Seven children experienced acute rejection episodes. All were reversible with increased doses of corticosteroid. One case of graft failure was caused by ischemic renal injury. Adverse events included Epstein-Barr viremia (8 patients) with three cases of post-transplant lymphoproliferative disease (PTLD), cytomegalovirus viremia (4 patients), poor wound healing (4 patients), pneumonitis (3 patients), nephrotic syndrome (3 patients), perinephric abscess (1 patient) and insulin-dependant diabetes (2 patients). Sirolimus was discontinued in 13 children for adverse events predominantly for wound dehiscence and pneumonitis. Cholesterol levels >200 mg/dL were observed in 33 children. Thrombocytopenia (platelet count <140 000) was not observed. We concluded that early outcomes with sirolimus were acceptable with 98% graft survival and 11% incidence of acute rejection. Medication was discontinued in 20% for adverse events which included poor wound healing and non-infectious pneumonitis. Infections with cytomegalovirus and Epstein-Barr virus, and PTLD were also significant early complications. Therefore, a sirolimus-based regimen that is combined with both an interleukin-2 receptor antibody and a calcineurin inhibitor may be excessive immunosuppression for pediatric renal transplant recipients.

Efficacy of nephrectomy for the treatment of nephrogenic hypertension in a pediatric population.

PURPOSE: We evaluated the efficacy of nephrectomy for the management of nephrogenic hypertension in children. MATERIALS AND METHODS: We retrospectively reviewed the records of 320 children who underwent nephrectomy between 1991 and 2001, and 22 underwent nephrectomy for the management of hypertension. Of the 22 patients 16 (73%) had long-term followup, including 8 with end stage renal disease who were dialysis dependent, and 8 with normal renal function and unilateral parenchymal renal disease (UPRD). Within the UPRD group 3 patients had renovascular hypertension, 3 had reflux nephropathy, 1 had renal artery thrombosis and 1 had Page kidney. Age at hypertension onset, age at nephrectomy and elapsed time between diagnosis and intervention were studied. Antihypertensive medication requirements before surgery and after postoperative followup were evaluated to assess treatment efficacy. Complete success was defined as blood pressure normalization without antihypertensive requirements. Partial success was defined as decrease in medication requirements and/or discontinuation of minoxidil. Failure of treatment was defined as persistent hypertension, increased medication requirements or minoxidil dependence. RESULTS: In the end stage renal disease group mean age at diagnosis was 5.9 years (range 15 months to 10 years) and bilateral nephrectomy was performed at a mean age of 8.9 years (19 months to 15 years) with average elapsed time between diagnosis of hypertension and nephrectomy of 3 years. After a mean followup of 4.4 years (range 6 months to 8 years) 7 patients (88%) experienced complete or partial success and nephrectomy management failed in 1. In the UPRD group average elapsed time was 2.2 years (range 1 month to 10 years) between a mean age at diagnosis of 6.7 years (birth to 16 years) and a mean age at nephrectomy of 8.9 years (1 month to 17 years). After a mean followup of 1.6 years (range 1 month to 5 years) complete or partial success was experienced by all 8 patients (100%). All 8 UPRD group patients experienced adequate residual renal function. CONCLUSIONS: The vast majority of patients in both categories experienced complete or partial success from nephrectomy for the management of medication refractory hypertension. Nephrectomy for hypertension control is safe and effective, and obviates the need for morbid medications. We continue to accrue patients in a prospective manner.

Predictors of cytomegalovirus disease among pediatric transplant recipients within one year of renal transplantation.

Cytomegalovirus (CMV) is the most important opportunistic infection in renal transplant recipients and is associated with an increased risk of rejection. Infection can be acquired post-operatively (from the transplanted organ) or from re-activation of latent disease. To identify risk factors for CMV disease in a pediatric population within 1 yr of renal transplant, and to generate hypotheses for the pathogenesis of CMV disease in this population, a review of all recipients from 1992 to 1998 in a children's hospital in Atlanta, Georgia, was undertaken. Medical records of 73 transplants performed on 72 patients were reviewed: nine (12.7%) of 72 individuals, after 73 procedures developed CMV disease. Median time to onset of CMV disease was 52 days post-transplant (range = 15-95 days). Receipts of mycophenolate mofetil (MMF), demographic factors, and use of cadaveric kidneys were not associated with a significantly elevated risk of CMV disease. Positive donor CMV serostatus was associated with CMV disease (uni-variate relative risk [RR] = 8.52, Fisher's Exact Test [FET] p = 0.010). Patients with transplants in October or November had a higher risk of developing CMV disease (four of 13; 30.8%) than patients transplanted in other months (five of 60, 8.3%); RR = 3.69; p = 0.047, FET). Most transplants of patients who did not develop CMV disease were performed in January through August (48/64; 75.0%); only 25.0% were performed in September through December. In contrast, six of nine (66.7%) transplants in patients who subsequently developed CMV disease were performed in September through December (p = 0.018, FET). Donor CMV-positive serostatus and transplant in October and November continued to be independently associated with an increased risk of CMV disease when controlled for other factors. The association of transplant in October and November with CMV disease in November-January may be related to an increased risk of seasonal community CMV exposure and primary CMV infection during the peak season for CMV circulation, with subsequent immune suppression promoting progression to disease. Alternatively, co-infection with seasonal pathogens after exposure from an infected donor during the period of immune suppression may promote progression from CMV infection to CMV disease. Further studies should be undertaken to explore these and other hypotheses, which may have implications for determination of a need for anti-viral prophylaxis.