Long-term outcome of children with steroid-resistant nephrotic syndrome treated with tacrolimus

We report the outcome of our single-center, long-term follow-up study of tacrolimus therapy in children with steroid-resistant nephrotic syndrome (SRNS). All cases of nephrotic syndrome (NS) with kidney biopsies treated at our center between January 2000 and July 2008 were reviewed. Children with systemic lupus erythematosus and steroid-dependent NS were excluded. Nineteen children with SRNS received tacrolimus. Histopathological analysis of the biopsy revealed the underlying conditions of these 19 patients to be focal segmental glomerulosclerosis (ten patients), C1q nephropathy (four), membranous nephropathy (two), minimal change disease (one), membranoproliferative glomerulonephritis (one), and immunoglobulin A nephropathy (one). The mean follow-up was 55 months, and the median age of the patient cohort was 10 years. We observed complete remission in 11 (58%) patients, partial remission in six (32%), and failure to respond in two (9%). The median time to response was 8 weeks. Side effects were mild and transient (one case of acute kidney injury and three cases of hyperglycemia). The initial rate for combined partial and complete remission of the NS in children with SRNS was 81%, which was sustained in 58% of the patients on follow-up. Among children with FSGS, the sustained remission rate was 50%, while 40% progressed to end-stage renal disease (ESRD) (mean time 52 months). Based on the results of this study, we conclude that tacrolimus is an effective and well-tolerated therapeutic option for the treatment of SRNS in children. However, the occurrence of relapses of the NS with progression to ESRD during the long-term follow-up indicates the need for careful monitoring of such patients.

Vasculitis in childhood

Systemic vasculitic syndromes are rare in childhood. Vasculitis is the predominant feature of a large number of different clinical entities that are linked by the presence of inflammatory changes in the blood vessels. The nature of these diseases and their relationship to each other remain unclear. The clinical presentation associated with the size of the affected vessels and epidemiological data are very helpful for the diagnosis of those diseases. Recent advances are beginning to shed some light on the etiology and pathogenetic mechanisms involved in the various vasculitides. There is good evidence to support roles for circulating immune complexes, cell-mediated immunity, anti-neutrophil cytoplasmic antibodies and anti-endothelial cell antibodies in the pathogenesis. Renal involvement in vasculitis in children is commonly seen in Henoch-Schönlein purpura, microscopic polyarteritis, Wegener's granulomatosis, Churg-Strauss syndrome and polyarteritis nodosa. However, kidney disease can also be part of the clinical picture of Kawasaki disease and Takayasu arteritis. Recently, with the institution of early and aggressive immunosuppressive treatment of severe cases, significant improvement in the long-term survival of patients has been achieved. This review article addresses the pathological and clinical features (particularly renal involvement), therapeutic intervention and prognosis of the above-mentioned diseases.

Serial evaluation of cell surface markers for immune activation after acute renal allograft rejection by urine flow cytometry--correlation with clinical outcome

BACKGROUND

The use of urine flow cytometry (UFC) as a noninvasive tool for the diagnosis of acute and chronic rejection of the renal allograft has been previously reported.

METHODS

We analyzed the expression of various cell surface antigens during a 30-day period after the diagnosis and treatment of 24 acute rejection (AR) episodes. UFC was performed on 59 urine specimens, from 17 patients meeting the diagnostic criteria for AR. UFC analysis was performed blinded to the clinical management utilizing the following fluorescinated monoclonal antibodies: anti-CD3, anti-CD14, anti-HLA-DR, anti-CD54, and anti-interleukin 2 receptor. Results were correlated with the patient's requirement for antilymphocytic drugs and increment in serum creatinine level (mg/dl) on day 30 after AR.

RESULTS

HLA-DR was the most prevalent antigen noted during the first 2 days of AR (91.7% of the samples), followed by CD14 (50%) and CD54 (41.7%). After day 4 the degree of expression of HLA-DR-, CD14-, and CD54-positive cells correlated with the need for antilymphocytic drugs. CD54 was the best parameter with a sensitivity=100% and specificity=90.9% (P=0.001). Those patients who had permanent graft injury after treatment of the AR had persistence of CD54- and CD14-positive cells in the urine.

CONCLUSION

Serial monitoring of urine sediments by UFC was predictive of the requirement for antilymphocytic therapy and irreversible graft damage.

Urine flow cytometry as a tool to differentiate acute allograft rejection from other causes of acute renal graft dysfunction

BACKGROUND

Recently, urine flow cytometry (UFC) was introduced as a useful noninvasive tool for the immunological monitoring of renal allograft recipients. The presence of an active urine sediment as determined by UFC was found to be associated with acute rejection (AR) episodes.

METHODS

In the present study we assess the value of UFC in the setting of acute graft dysfunction. UFC was performed in 30 patients (32 events) at the time of admission to the hospital for the evaluation of rising creatinine (serum creatinine increment > or =0.6 mg/dl above baseline). UFC analysis was done blinded to the clinical diagnosis, and results were compared with the discharge diagnosis: AR, n=15; chronic rejection (CR), n=8; drug toxicity, n=4; urinary leak, n=2; recurrence of primary disease, n=1; lymphocele, n=1; and unknown, n=1.

RESULTS

The presence of at least 5% of HLA-DR-positive cells and intercellular adhesion molecule-1-positive cells was detected in 100% and 53%, respectively, of the samples associated with AR (P<0.01 vs. others). The specificity value for the diagnosis of AR was: 100% for the presence of intercellular adhesion molecule-1 or CD3-positive cells and 88% for the presence of interleukin-2 receptor-positive or HLA-DR-positive cells. Half of the samples associated with CR had CD14-positive cells (P=0.03 vs. others) with a specificity value of 87.3%. The samples associated with drug toxicity, urological problems, or recurrence of primary disease were remarkable for the lack of expression of the antigens studied.

CONCLUSION

UFC can clearly differentiate AR from other causes of acute renal allograft dysfunction. HLA-DR is revealed to be the most sensitive and intercellular adhesion molecule-1 the most specific marker for AR. The presence of CD14-positive cells was highly suggestive of CR. Due to its objective nature, UFC should be considered in the evaluation of graft dysfunction.

A comparative analysis of the use of mycophenolate mofetil in pediatric vs. adult renal allograft recipients

Mycophenolate mofetil (MMF) is a new immunosuppressive drug used in combination with cyclosporin A (CsA) or tacrolimus and prednisone to prevent rejection of renal allografts in both adult and pediatric recipients. It has been shown in several large studies that MMF significantly decreases the incidence of acute rejection in adults and has acceptable adverse effects. In this retrospective study, we compare the incidence of adverse events between pediatric and adult renal allograft recipients. Twenty-two children and 37 adult renal allograft recipients were included in the study. The initial dose of MMF was 1.5 g b.i.d. for the adult patients and ranged from 15 to 30 mg/kg/d for the pediatric patients. All patients received p.o. acyclovir as prophylaxis for cytomegalovirus (CMV). The two groups were similar regarding gender distribution and graft source. Acute rejections occurred in 10 of the 22 pediatric patients (45%) and in nine of the 37 adults (24%), p = NS. The incidence of infections was similar in both groups except for the occurrence of CMV (n = 5), which was seen only in adults. The incidence of GI symptoms was significantly higher in the pediatric population (54.5% vs. 21.6%; p = 0.02). Significant weight loss was seen more often in the smaller pediatric patients (weight < or = 15 kg) compared to the larger pediatric patients, 60% vs. 11.7%, p = 0.05. Among the patients who had significant GI symptoms 50% of the adults and 75% of the pediatric recipients required either dose reduction or, most commonly, discontinuation of the MMF. The need to discontinue MMF was significantly higher in the pediatric patients, especially in those that weighed less than 15 kg. We suggest the possibility that the optimum dose, dosing interval or preparation of MMF has not yet been established for pediatric patients. One should therefore monitor pediatric patients closely, especially the small ones, to avoid significant nutritional problems and other adverse GI events.

Successful rescue of refractory acute antibody-mediated renal allograft rejection with splenectomy--a case report

Highly sensitized patients receive fewer kidney transplants and have a high risk for severe rejection with increased rates of graft loss. We present a highly sensitized child who after desensitization protocol received a kidney transplant and developed refractory acute antibody-mediated rejection. He failed to respond to standard therapy and needed an urgent splenectomy as rescue therapy. Our patient, an 18-yr-old AA male with ESRD due to obstructive uropathy received a second DD transplant. The allograft functioned immediately with SCr 1.4 mg/dL on day #5. On day #8, he was re-admitted with fever, oligoanuria, and renal failure. He was started on methylprednisolone pulse, thymoglobulin, intravenous immunoglobulin, and PP. The transplant kidney biopsy revealed features suggestive of acute AMR. On day #14, the patient remained dialysis dependent with no response to therapy. He underwent an urgent splenectomy and a slow increase in urine output and GFR was noted. The SCr one month post-splenectomy was 1.1 mg/dL. At one yr post-txp, his GFR remained stable with SCr 0.9 mg/dL on tacrolimus, mycophenolate mofetil, and prednisone. Urgent splenectomy successfully reversed refractory acute AMR, in our highly sensitized patient with second renal transplant.

Lymphocyte ATP immune cell function assay in pediatric renal transplants: is it useful?

The ultimate goal for an allograft is a balanced immunosuppression to provide the longest graft survival with minimal side effects. In this retrospective study, we correlate the immunosuppresion level as determined using the Cylex assay (Immu know, Columbia, MD) with clinical events. Demographic data such as age at the time of transplant, gender, ethnicity, time posttransplantation, tacrolimus level, and induction therapy were correlated with Cylex levels. Cylex from children with an infection or acute rejection were compared to those from stable patients. All children received induction with basiliximab or thymoglobulin followed by a standard regimen with tacrolimus, steroids, and mycophenolate mofetil. Fifty-nine Cylex results were obtained in 44 pediatric renal transplant recipients. Cylex values ranged from 20 ng/mL to 728 ng/mL. We did not find significant correlation between any of the demographic characteristics studied (tacrolimus level, induction therapy, acute rejection, and Cylex levels). Fifteen patients had severe infections requiring hospitalization: 11 of 15 (73%) had Cylex<130 ng/mL; these levels differed significantly from those obtained in patients without infections. We concluded that clinical utility of Cylex is limited in children with kidney transplants because it did noes correlate with the prescribed dosage of medications or with rejection. However, low Cylex levels were highly correlated with serious infections.

Impact of laparoscopic donor nephrectomy on allograft function in pediatric renal transplant recipients: a single-center report

Laparoscopic donor nephrectomy (LDN) is rapidly becoming the preferred technique for the procurement of living donor kidneys. An association of this technique with delayed graft function and higher risk for rejection has been reported in pediatric recipients. We reviewed our experience of 17 pediatric patients who received a living donor kidney, from 2002 to 2004, procured by LDN, and compared it with a matched group that received living donor kidneys harvested by the open technique. Patient demographics, etiology of renal failure, intra-operative events, length of stay, serum creatinine decline, and graft function were reviewed. Our experience confirmed the findings of earlier reports specifically in small pediatric recipients. The LDN group showed a significantly slower decline in creatinine in the immediate post-operative period and longer intra-operative time. However, there was no difference between the two groups in the length of hospital stay, and creatinine clearances at discharge, six, 12 and 24 months post-operatively. The incidence of acute rejection was similar in both groups. LDN is a safe procurement modality for pediatric patients. The risk for prolonged OR time and delay graft function has to be considered during the evaluation process.

A single-center study of C1q nephropathy in children

C1q nephropathy (C1qN) is a rare idiopathic glomerulopathy typically seen in adolescents and young adults. All kidney biopsies done from 2002 to 2007 were analyzed (264). Thirteen cases of C1qN from 212 (6.6%) native biopsies and one case out of 52 (1.9%) transplant biopsies were reviewed regarding demographic features, clinical presentation, histopathology, treatment, and outcome. Age varied from 1 to 18 years; half were boys. Ten children (71.4%) presented with nephrotic syndrome (NS). The most common histopathology found was diffuse mesangial proliferative glomerulonephritis (DMP) by light microscopy (LM), with diffuse granular staining for C1q predominantly in the mesangium. Children with either NS or persistent gross hematuria received prednisone and angiotensin-converting enzyme inhibitors (ACEi) (11). Median follow-up was 36 months. Steroid response was complete in 6 patients (54.5%). Those with steroid resistance (5) or steroid dependence (2) received further immunosuppression with mycophenolate mofetil (MMF) or tacrolimus (Tac). Three children achieved complete remission and four partial remission. Frequent relapses were seen in 4/14 patients. Renal survival was 100%. Our report reveals a high incidence of C1qN in pediatric patients, with variable clinical presentation. Despite a high incidence of steroid resistance among those with NS, an excellent response was observed with the addition of further immunosuppression.

May-Thurner syndrome in a pediatric renal transplant recipient--case report and literature review

Vascular complications post-renal transplantation are not very common and can be associated with increased risk of graft loss. We report an unusual case of a young, female teenager with asymmetrical leg swelling. After one month of transplantation, the patient developed a rise in serum creatinine with right leg swelling (ipsilateral to transplant) from compression of the iliac vein by a right renal transplant lymphocele, which resolved after lymphocele drainage. Subsequently, left leg swelling (contralateral to transplant) was noticed and the diagnosis of May-Thurner syndrome was made by MRV. The patient was successfully managed with oral Plavix, stockings and leg elevation. The allograft function remained stable at 18 months post-transplant.

Evidence that the systematic analysis of bile cytology permits monitoring of hepatic allograft rejection

Cytologic analysis was performed on 128 bile specimens collected by schedule from 12 liver transplant recipients over a 4-month period. Clinical diagnoses at the time of specimen collection were determined retrospectively, as follows: clinically stable, 75; acute rejection, 15; CMV hepatitis, 1; systemic infection, 8; ischemic injury, 24 (all within the first 4 days postop); nonclassifiable, 5. Bile analysis was done by a blinded investigator. Specimens contained ductal epithelial cells (EC) and inflammatory cells (IC), which were counted using Cytospin slide preparations. Greater than 10 cells/slide were seen in 93.3% of rejections, 91.7% of ischemic injuries, 100% of systemic infections, and 14.6% of stable patients. In samples collected after POD 4, IC were seen in 86.7% of rejections, yielding a specificity of 94.4% (P less than 0.001). If lymphoblastic cells were also seen, the specificity increased to 96.6%. Five specimens were obtained the day before the clinical diagnosis of rejection; all demonstrated IC. Seven specimens were obtained 3 days after beginning therapy for rejection. In 5 the bile contained no IC, and clinical improvement occurred; in the 2 in whom IC were found, further therapy was subsequently required. IC were seen in 5 of 8 specimens taken when systemic infection was present; the clinical setting allowed differentiation from rejection. Only 1 case of CMV hepatitis was included, thus no conclusions can be drawn for this entity. Cytoplasmic vacuolization of EC was observed in 30% of cases, in these, cyclosporine levels were significantly higher (989.9 +/- 356.9 vs. 672.8 +/- 421.2, P = 0.02). In summary, bile cytology analysis aides in the monitoring of the onset and duration of rejection. It may be an indicator of persistent rejection, and it may help prevent overimmunosuppression in those cases with normal cytological findings.

Urine flow cytometry as a predictor of renal allograft function

The value of urine flow cytometry (UFC) in diagnosing acute renal allograft rejection (AR) was recently established in a prospective double-blind study. In this study, we report the 1-year follow-up of three groups of patients identified during the previous study: group 1--stable patients (no ARs) with persistently negative UFCs (n=7); group II--patients who had early ARs (<3 months after transplantation), with positive UFCs that completely normalized with antirejection therapy (n=8); group III--stable patients (no ARs) with positive UFCs (n=7). By definition, group III consists of patients previously considered to have "false positive" UFCs. All patients received standard immunosuppressive therapy, with regimens that included cyclosporine at doses adjusted to maintain target levels. Serum creatinine (SCr) levels (mg/dl) were similar in all three groups at 1 month after transplantation. However, at 1 year after transplantation, SCr was 1.4 +/- 0.2 in group I, 2.0 +/- 0.9 in group II, and 1.9 +/- 0.3 in group III (P=0.004 group I vs. group III). There were no ARs clinically diagnosed during this follow-up period in any of the three groups of patients, but there were significantly higher SCr increments among group III patients after the 1 year of follow-up. The detection of an active urine sediment by flow cytometry in "clinically stable" allograft recipients may indicate ongoing, subclinical acute rejection activity, which in this study was found to be associated with worse renal function at the end of the first posttransplant year as compared with patients with persistently negative UFCs. Increased immunosuppression may be indicated for these patients with persistently positive UFCs.

Successful treatment of severe acute antibody-mediated rejection of renal allografts with bortezomib--a report of two pediatric cases

aAMR in renal allografts is uncommon and remains a challenge as it is often refractory to treatment modalities. Aggressive therapy is essential to reverse the rejection as it results in renal allograft loss in approximately 27-40% of cases. There are anecdotal case reports of use of bortezomib, a proteasome inhibitor in the treatment of resistant AMR cases in solid organ transplant recipients; however, the experience is limited. We herein report successful reversal of resistant aAMR in two pediatric patients with bortezomib. Patients were initially treated with IV methylprednisolone pulse therapy with IVIG and PP three times weekly for a total of 10 treatments. After the standard therapy used at our institution persistence of DSA associated with graft dysfunction prompted the use of bortezomib to further treat the rejection. We did not have any neurologic side effects, but one patient did experience significant infections after bortezomib infusions requiring prolonged antimicrobial therapy. The long-term outcome of both children was excellent with preservation of normal renal function and persistent reduction in DSA titers.

Donor-specific antibodies by flow single antigen beads in pediatric living donor kidney transplants: single center experience

Flow PRA and SAB are now routinely performed to identify HLA antibodies in the recipient sera. The presence of DSA is considered a risk factor for graft failure. However, this risk is not clearly defined. We reviewed all the pediatric recipients of living donor kidney transplants since Flow PRA and Flow SAB became routinely done at our institution. All children had negative CDC and Flow XMs. Comparison of clinical outcome was done between those with and without pretransplant DSA. Six children had positive DSA by Flow SAB. They received thymoglobulin, steroids, tacrolimus, and MMF. Five had anti-HLA class I antibodies and one anti-HLA class II. Only one child had an AR. Graft survival: 100% at last visit with GFR >70 mL/min/1.73 m(2). A control group without DSA was used for comparison (n = 44). They received our standard protocol: basiliximab, tacrolimus, MMF, and steroids. AR rate was 9%. Both groups had similar follow-up time, and patient and graft survival rates. In our small series, we saw excellent outcome despite the presence of DSA pretransplant. No unequivocal ideal to establish the ideal immunosuppressive regimen for this cohort of patients has been established and the long-term outcome of these recipients has not been delineated.

Anuria since birth: does it impact outcome of kidney transplant in infants?

Kidney transplantation (txp) in infants has recently made much progress but provides a unique challenge in infants anuric since birth. Little data exists on outcome of renal txp recipients with anuria since birth. Retrospective chart review was done for outcome of 27 children with wt ≤15 kg and they were divided into two groups: Group A (N=21) with urine output and Group B (N=6) anuric since birth had their urological complications and long-term outcome compared. Median age at the time of txp 18 vs 23 months, mean wt 10.8 vs 11.8 kg, and mean ht 77 cm in both, mean follow-up post-txp: 9.4 vs 5.6 years, and neurological problems were noted in 48% and 33% in Group A and Group B. There was no graft thrombosis or post-transplant lymphoproliferative disease and only two rejections. Anuric Group B were older, had more post-txp urological surgeries (66% vs 19%) and UTIs (66% vs 38%) compared to Group A. The overall graft survival at 1, 5, and 10 years was 96%, 86%, and 70%; patient survival at 1, 5, and 10 years was 96%, 85%, and 85%. Long-term graft outcomes in small children, anuric prior to txp, were excellent despite higher rates for UTIs and urological complications.

C1q nephropathy in a child with a chromosome 13 deletion

C1q nephropathy (C1qNP) is a rare cause of childhood nephrotic syndrome (NS). We describe a child with retinoblastoma, lipomyelomeningocele and a chromosome 13 deletion who presented with massive proteinuria due to C1qNP. Despite steroid resistance, successful treatment of the NS was achieved with mycophenolate mofetil.

Immune-mediated nephropathies in kidney transplants: recurrent or de novo diseases

IMN contribute to ESRD in 13% children with renal transplant (txp). Recurrent or de novo IMN can cause graft dysfunction and/or failure, but the details regarding incidence, therapy, and outcome remain poorly understood. Retrospective single-center study of all pediatric kidney txp was carried out since 1998. Clinical presentation, pathology, therapy, and graft outcomes of children with recurrent or de novo IMN were reviewed. IMN was the primary etiology of ESRD in 28 of the 149 txp recipients. Eleven children had biopsy-proven post-txp IMN-six were recurrent and five had de novo. Presentation varied with changes in SCr and/or proteinuria. Initial therapy included higher doses of steroids, MMF, and tacrolimus. Outcome was excellent with only one late graft loss. Full remission was achieved in all other patients, but some had re-recurrence of the IMN. Median follow-up time was 11.8 years. IMN (recurrent or de novo) occurred in 7.4% (11 of 149) of all kidney txp performed at our center. IMN post-txp was often seen late post-txp, usually asymptomatic and noted to have relapsing pattern. Early diagnosis and prompt therapy resulted in excellent long-term outcome in children diagnosed with post-txp IMN.

Risk of steroid withdrawal in pediatric renal allograft recipients (a 5-year follow-up)

Withdrawal of steroid therapy in renal allograft recipients remains controversial despite the many side effects of this treatment. We have previously presented data on 16 pediatric renal transplant recipients in whom prednisone was withdrawn 6 months or later post-transplantation. To assess the impact of steroid withdrawal, we retrospectively compared this group of patients (Group 1) with a group of 12 patients (Group 2) with renal transplants who continued on prednisone. The groups were compared as to age, sex, ethnicity, source of graft, number of HLA-DR mismatches and incidence of ATN in the immediate postoperative period. The only significant difference was that Group 2 was older. Group 1 had significantly fewer episodes of early acute rejection in the first 6 months post-transplantation than the control group (3/16 vs 8/12, p = 0.009) but nevertheless, without prednisone, had significantly more late acute rejections (11/16 vs 3/12, p = 0.03). Acute rejections occurred as late as 4 years after withdrawal of steroids. Only 5 of the 16 patients in Group 1 have maintained stable graft function without steroids. All of these patients are now alive more than 5 years after steroid withdrawal. In comparing these patients to the other 11, who failed a trial of steroid withdrawal, we found that a serum creatinine of less than 1.7 mg/dl at the time of withdrawal of steroids was predictive of a successful outcome (p = 0.03). In conclusion, withdrawing steroids in pediatric renal allograft recipients has a high risk of late acute rejection and subsequent graft loss, especially for those who have higher baseline creatinine levels.

Comparative value of urinalysis, urine cytology and urine sIL2R in the assessment of renal disease in patients with systemic lupus erythematosus (SLE)

Serial immunological testing has been recently proposed for monitoring patients with lupus nephritis as routine serological tests have shown sub-optimal correlation with clinical status. To assess the value of urine cytology and urine sIL2R in the evaluation of patients with SLE, in particular those with lupus nephritis, we conducted a prospective double-blind study of 31 patients with SLE, during an 18-month period. A comparison of routine urinalysis with urine cytology and urine sIL2R was performed in 84 samples: 15 from patients without a history of renal involvement and 69 from patients with a history of renal involvement. A high urine cytology score (> or = 6), particularly in the presence of lymphoblasts, plasma cells or monocytes, was significantly associated with lupus nephritis in relapse. Urine sIL2R levels were significantly elevated during all SLE relapses, unrelated to the presence of renal involvement. Fifteen urine specimens were obtained at the time of a kidney biopsy: 9 with active lesions and 6 with inactive renal disease. UC score was 2.0 +/- 1.89 for those with absent activity, 8.4 +/- 3.4 for mild activity and 11.0 +/- 2.4 for moderate/severe activity (p < 0.001 between active vs inactive disease). No urinalysis parameter alone permitted distinguishing the degree of renal disease activity. In the subgroup of patients with renal disease urinalysis was overall less accurate than urine cytology or urinary sIL2R levels for predicting renal disease activity defined by biopsy. Urine cytology and urine sIL2R proved to be reliable measures of lupus activity.

Urine cytology and urine flow cytometry in renal transplantation--a prospective double blind study

Urine cytology (UC) has proved to correlate well with core and fine-needle aspiration kidney biopsies of renal allograft recipients undergoing acute rejection (AR). This study was undertaken to compare the relative usefulness of urine flow immunocytometry (UFC) (using fluorescinated antibodies anti-HLA-DR, anti-CD3 and antirenal epithelial cells) with UC in its ability to diagnose AR by analyzing 200 urine specimens during a prospective double-blind study of 40 renal transplant recipients. Clinical diagnosis was retrospectively assigned to one of the following categories: group I--AR, 15; group II--ischemic injury period (first 5 days postop.), 12; group III, 173 (including 168 stable grafts, 1 pyelonephritis and 4 cyclosporine toxicity), by investigators blinded to the urine results. Both tests were highly sensitive for the diagnosis of AR (UC = 86.6% vs. UFC = 100%; P = NS) with a specificity after the ischemic injury period of 78% by UC and 87.9% by UFC. Samples obtained during AR revealed higher levels of expression of HLA-DR as well as higher numbers of CD3-positive cells. These tests had specificity values of 95.3% and 97.6%, respectively, for the diagnosis of AR. The degree of immune activation (established by numbers of lymphocytes/lymphoblasts seen by UC) correlated with the severity of biopsy-proven ARs and with response to antirejection therapy. In conclusion, both test are highly accurate in diagnosing AR. The highest specificity value was obtained when both UC and UFC were utilized together (93%). We suggest that the routine use of these tests can provide an important adjunct to the evaluation of renal transplant recipients.