No increase in rejection or graft loss in kidney transplant recipients with thrombophilia treated with anticoagulation and triple immunosuppression.

INTRODUCTION: Recent studies from Europe have demonstrated that patients with end-stage renal disease who receive a kidney transplant are at an increased risk for rejection and graft loss when compared with patients who have no known thrombophilia. The role of anticoagulation has not been investigated in these patients. MATERIALS AND METHODS: We prospectively tested patients who were evaluated for a kidney transplant for 8 thrombophilias, protein S and C deficiencies, factor V Leiden mutation, antithrombin III deficiency, anticardiolipin antibody, lupus anticoagulant, prothrombin gene mutation, and heparin-induced platelet antibody (HIPA). Patients with any identified thrombophilia received heparin or argatroban (for HIPA (+) patients) followed by coumadin for 1 year after transplantation. Triple therapy included cyclosporine, prednisone, and CellCept (Roche Pharmaceuticals, Nutley, NJ, USA). Sensitized, black, or repeat transplantation patients received induction with an interleukin (IL)-2 inhibitor. Data were collected in a retrospective manner. Rejection was biopsy-proven. RESULTS: Of the 112 transplant recipients who were tested for thrombophilia, 37 had 1 or more thrombophilia and 75 had no thrombophilia identified. Twenty-six patients received heparin and 11 received argatroban. There were no differences in recipient age, cold storage time, graft loss, HLA match, rejection episodes, 1-year graft survival, or serum creatinine level at 1 year. Significant differences were noted in posttransplantation bleeding, 35% versus 5%, and delayed graft function, 32% versus 15%, in patients with thrombophilia versus no thrombophilia, respectively. CONCLUSION: This is the first study to demonstrate that there is no increase in rejection or graft loss in kidney transplant recipients with thrombophilia when treated with anticoagulation and triple immunosuppression.

Development of diabetes mellitus post-renal transplantation is associated with poor short-term clinical outcomes.

BACKGROUND: Although posttransplant diabetes mellitus (PTDM) is associated with poor long-term outcomes short-term outcomes are not well studied in renal transplant recipients (RTRs). METHODS: RTRs between January 1999 and December 2000 (n = 181) stratified according to the occurrence of diabetes mellitus (DM), namely, non-DM (n = 72), previous DM (n = 88), and PTDM (n = 21) were compared for infections, hospital readmissions, and graft rejections during the first 6 months posttransplantation. RESULTS: PTDM showed patients affected by a significantly higher rate of infections (57.1% vs 29.2%) and recurrent infections (28.5% vs 11.1%) compared to non-DM and a trend toward an increase compared to previous DM. PTDM patients had a significantly higher incidence of multiple readmissions compared to both previous DM (52.4% vs 20.5%) and non-DM (52.4% vs 23.6%). Subjects with PTDM showed a significantly higher occurrence of rejection (28.6% vs 9.1%) and recurrent rejection (14.3% vs 2.3%) than previous DM and a greater trend compared to non-DM. CONCLUSION: PTDM is associated with poorer short-term outcomes than either non-DM or previous DM.

Surgical site infections following pediatric liver transplantation: risks and costs.

PURPOSE: Infectious complications following orthotopic liver transplantation (OLT) represent a significant cause of morbidity and mortality in both adults and children. In adults, surgical site infections complicating OLT have been shown to significantly increase resource utilization, but their impact in children has not been studied. In this study we identify risk factors for surgical site infections in children undergoing primary OLT for end-stage liver disease and estimate their impact on patient survival, graft survival, length of stay, and charges. METHODS: All pediatric liver transplants (n = 77) less than 16 years of age from the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) Liver Transplantation Database were included in the analysis. Surgical site infections (n = 25) were defined as wound infections, abdominal abscesses, and bacterial or fungal infections of the liver, intestine, or peritoneum during the initial transplant admission. Risk of infection was estimated using logistic regression, survival rates were estimated using the Kaplan-Meier method, and length of stay and charges were compared using Student's t-test. Multivariate analysis of charges was performed using linear regression. RESULTS: Of the 77 patients, 25 (32.5%) developed a surgical site infection. Several factors were associated with increased risk of infections, including a leak at the biliary anastomosis (odds ratio [OR] 115, P = 0.003), preoperative white blood cell count (OR = 1.28, P = 0.009), surgery > 7 h (OR = 15.0, P = 0.011), HLA mismatches (OR = 6.0, P = 0.03), and female gender (OR = 8.0, P = 0.038). Surgical site infections did not significantly decrease either patient survival or graft survival, and increased hospital stay by an average of 21 days (P = 0.14). After controlling for other factors, patients who developed surgical site infections incurred on average $132,507 (P = 0.03) more in charges than patients who did not develop infections. CONCLUSIONS: Surgical site infections in pediatric patients following liver transplantation are significantly influenced by surgical technique and endogenous patient characteristics. Though survival outcomes are not different, the development of such infections has significant implications for resource utilization in the care of these patients.

The effect of surgical site infections on outcomes and resource utilization after liver transplantation.

BACKGROUND: Although postoperative infections have a significant impact on morbidity and mortality after orthotopic liver transplantation (OLT), less is known about their economic implications. In this study, we sought to identify risk factors and estimate the impact of surgical site infections on 1-year mortality, graft survival, and resource utilization after OLT. METHODS: We studied 777 first, single-organ liver transplant recipients from the National Institute of Diabetes and Digestive and Kidney Diseases Liver Transplantation Database. Surgical site infections (n = 292, 37.8%) were defined as bacterial or fungal infections of the liver, intestine, biliary tract, surgical wound, or peritoneum within 1 year of transplantation. A subset of these (n = 159) occurred during the transplant hospitalization and were used to estimate excess charges associated with surgical site infections. RESULTS: Leaks in the choledochojejunostomy (odds ratio [OR] = 7.1, P =.001) and choledochocholedochostomy (OR = 2.5, P =.002), extended operation duration in hours (OR = 1.2, P =.002), serum albumin levels in grams per liters (OR = 0.71, P =.009), ascites (OR = 1.43, P =.037), and administration of OKT3 within 7 days (OR = 1.49, P =.039) significantly increased risk of infection. Surgical site infections did not significantly increase 1-year mortality (88.5% vs 91.5%, P =.19) but significantly increased 1-year graft loss (79.8% vs 86.5%, P =.022). Patients with surgical site infections incurred approximately 24 extra hospital days and $159,967 in excess charges (P =.0001). Multivariate analysis reduced the estimate of excess charges to $131,276 (P =.0001). CONCLUSIONS: Liver transplant recipients who develop surgical site infection have significantly higher resource utilization requirements than those who do not. These results imply substantial returns to preventative efforts directed at surgical site infections in patients undergoing OLT.

The dual kidney transplant registry.

There has been a steady increase in the utilization of aged donor kidneys for dual transplantation during the past several years. As the follow-up of these dual kidney recipients accrues, it is clear that the long-term graft survival rate approaches that seen in recipients of single kidneys transplanted from younger donors. Because the kidneys used for dual kidney transplants would have otherwise been discarded, it is imperative to recognize that kidneys from cadaver donors that fall outside the normal acceptance criteria are a valuable resource and can provide excellent long-term function when properly placed. Reducing cold storage time may be the single most important aspect to insuring long-term graft survival in recipients of aged dual kidney transplants.

Evaluation of the older cadaveric kidney donor: the impact of donor hypertension and creatinine clearance on graft performance and survival.

BACKGROUND: The use of older donors for cadaveric renal transplantation (CRT) remains controversial because older donors are associated with decreased graft survival, yet offer the opportunity for donor pool expansion. We investigated the impact of two age-related donor factors, hypertension and calculated creatinine clearance (C(Cr)), as predictors of graft outcome in recipients of CRTs from donors > or =55 years of age. METHODS: We reviewed 33,595 recipients of CRTs reported to UNOS since 4/1/94, of which 4,732 were from donors aged > or =55 years. Outcome measures were graft survival, serum creatinine, and incidence of delayed graft function with 3 years of follow-up. We first analyzed the effect of hypertension on outcome from donors > or =55 years: 2679 donors had no hypertension, 1058 had hypertension < or =10 years, and 557 had hypertension > 10 years. Next, the effect of donor C(Cr) as a risk predictor was investigated. Based on this analysis, recipients of older donors were grouped into two cohorts for comparison: 2570 donors with C(Cr)<80 ml/min and 2162 donors with C(Cr) > or =80 ml/min. RESULTS: Actuarial graft survival from donors aged <55 years was 88.0, 83.4, and 78.5% at 1, 2, and 3 years, vs. 80.6, 73.5, and 65.3% from donors > or =55 years (P<0.0001). When stratified by hypertension, older donors hypertensive > 10 years had survivals of 77, 66, and 57% vs. 81, 73, and 65% from donors without hypertension (P<0.017) and 80, 74, and 66% from donors hypertensive <10 years (P<0.017). When stratified by C(Cr), older donors with C(Cr) <80 ml/min had survivals of 77, 69, and 62% vs. 83, 76, and 66% from donors with C(Cr) > or =80 (P<0.0001). Finally, older donors with both hypertension > 10 years and C(Cr) <80 ml/min had survivals of 77, 61, and 53%. CONCLUSIONS: Long-standing hypertension and low calculated creatinine clearance are risk factors for decreased graft survival of CRTs from older donors. When both factors are present, graft survival is significantly decreased.

Prolonged cold ischemia time obviates the benefits of 0 HLA mismatches in renal transplantation.

HYPOTHESIS: Recipients of 0 HLA mismatch kidneys with prolonged cold ischemia times of longer than 36 hours do not have superior outcomes compared with recipients of kidneys with 1 or more mismatches. DESIGN: Retrospective review. SETTING: Transplanation centers. PATIENTS AND METHODS: A total of 63,688 recipients who underwent transplantation between January 1, 1990, and July 31, 1998. MAIN OUTCOME MEASURES: Delayed graft function, serum creatinine level, and patient and renal graft survival. RESULTS: Recipients of 0 HLA mismatch kidneys with fewer than 36 hours of cold ischemia time had better 5-year graft survival (75%) when compared with recipients with 1 or more mismatches (67%) (P<.001). However, recipients of 0 HLA mismatch kidneys with longer than 36 hours of cold ischemia time did not have any graft survival advantage (71% in 0 HLA mismatch kidneys vs 72% in 1 or more mismatches, P =.24). CONCLUSIONS: Cold ischemia times of longer than 36 hours obviate the benefits of better graft survival conferred by better matching.

The effect of age and prolonged cold ischemia times on the national allocation of cadaveric renal allografts.

BACKGROUND: National sharing of cadaveric renal allografts for perfectly matched kidneys (0 antigen mismatch) has improved outcome in the recipients of these kidneys despite increasing cold storage times. However, there may be limits to outcome improvement of matched kidneys based on age and cold storage time. MATERIALS AND METHODS: To determine if national sharing of kidneys based on matching improves outcome regardless of donor age and cold storage time, we evaluated the United Network for Organ Sharing (UNOS) Scientific Registry for all recipients of cadaveric kidney transplants between January 1, 1990 and July 31, 1998. We divided the recipients into four groups based on donor age and cold storage time. Group 1 comprised young donors (donor age <55 years) with average (<24 h) cold storage time; group 2, young donors with long (>/=24 h) cold storage time; group 3, older donors (donor age >/=55 years) with average cold storage time; and group 4, older donors with long cold storage time. RESULTS: A total of 64,046 recipients were evaluated: 35,061 (55%) in group 1, 21,264 (33%) in group 2, 4308 (7%) in group 3, and 3414 (5%) in group 4. Early graft performance progressively decreased from group 1 to group 4. Delayed graft function (DGF: dialysis requirement in the first 7 days posttransplant) was 18, 29, 33, and 42% (P < 0.0001); serum creatinine at 3 years (in mg/dl) was 1.70 +/- 0.8, 1.73 +/- 0.9, 2. 31 +/- 1.0, and 2.42 +/- 1.1 (P < 0.0001); 1-year graft survival was 87, 84, 79, and 77% (P < 0.0001); and 3-year graft survival was 77, 74, 63, and 62% (P < 0.0001, for groups 1 and 2 vs groups 3 and 4, respectively). The trends in DGF persisted through the groups in 0 antigen mismatched kidneys. CONCLUSIONS: Early function is adversely affected by prolonged cold storage, despite matching, in recipients of younger and older donor kidneys. Long-term function does not appear to be affected by prolonged cold storage. Recipients of kidneys from donors >/=55 years of age have significantly worse short- and long-term outcome and may not benefit from national sharing.

Outcome in recipients of dual kidney transplants: an analysis of the dual registry patients.

BACKGROUND: A novel but controversial method to increase the utilization of aged donor kidneys is the transplantation of both kidneys as a dual transplant. Initial single-center reports demonstrated outcomes similar to single kidneys from younger donors. In this report, we compare outcome in recipients of kidneys from donors > or =54 years of age who received a single kidney transplant reported to the United Network for Organ Sharing Scientific Registry versus a dual kidney transplant reported to the Dual Kidney Registry. METHODS: A retrospective analysis was performed, comparing four donor and nine recipient and outcome variables between recipients of a single versus a dual transplant between March 1993 and March 1999. RESULTS: Dual versus single transplants from donors > or =54 years of age have a significantly decreased incidence of delayed graft function, and lower serum creatinines up to 2 years after transplant despite having kidneys from significantly older donors with poorer HLA matching. CONCLUSIONS: Dual kidney transplants improve graft performance and outcome in recipients of kidneys from donors > or =54 years of age.

Severe glomerular sclerosis is not associated with poor outcome after kidney transplantation.

BACKGROUND: The increased utilization of expanded criteria kidney donors has necessitated the reevaluation of multiple donor risk factors to insure the best outcome from this valuable resource. Reports of decreased graft survival in recipients of kidneys from donors with > or =20% glomerular sclerosis (GS) have led many transplant centers to refuse these donor kidneys. The purpose of this study is to compare outcome in recipients of cadaveric donor kidneys with > or =20% GS versus those with <20% or no GS at our center. METHODS: We retrospectively reviewed 18 donor and 19 recipient and outcome variables in 89 recipients of kidneys, which were biopsied at the time of transplantation, between February 1995 and November 1998. We evaluated outcome based upon the percent of GS and the degree of vasculopathy. RESULTS: Donors with > or =20% GS were older and had more hypertension. Recipients of kidneys with > or =20% GS were older, had higher serum creatinine values at 1 and 2 years, but similar rates of delayed graft function and 2-year graft survival. Vasculopathy did not correlate to any important donor criteria except the percent GS. However, serum creatinine was significantly higher in recipients of kidneys with moderate vasculopathy versus none, up to 2 years after transplantation. There was no significant difference in graft loss based upon vasculopathy. CONCLUSION: Kidneys from donors with > or =20% GS provide excellent outcome similar to kidneys from donors with no GS.

A new, unique and simple method for ureteral implantation in kidney recipients with small, defunctionalized bladders.

BACKGROUND: Major, almost insurmountable, deterrents exist to the use of the small capacity, defunctionalized, nonneurogenic urinary bladder in renal transplantation, namely, the technical difficulty in performing a satisfactory ureteral implantation with conventional methods and the potential secondary problems with high grade ureteral reflux and obstruction. Alternatives are less than ideal and include transplantation into a bowel-augmented urinary bladder with intermittent self-catheterization, ileal conduit urinary diversion, or avoidance of transplantation and relegating the patient to life-long dialysis. METHODS: Eight consecutive patients (ages 13 months to 29 years) with small, defunctionalized urinary bladders underwent a new method of intravesical implantation of the transplant ureter. The mean capacity of these bladders was 18.5+/-13.1 ml (range 6 to 45 ml), with the bladders defunctionalized for a mean 81.6+/-24.3% of the patients' total lifetime. The technique involved placement of the transplant ureter into a shallow, mucosa-denuded, rectangular trough extending from a superiorly placed ureteral hiatus distally to the trigone. We hypothesized that the mucosal margins on the two lateral aspects of the rectangular trough would grow over the anterior surface of the ureter until they met the advancing mucosal edges from the contralateral side to form a natural neosubmucosal tunnel. RESULTS: Posttransplantation cystoscopic examination demonstrated bladder mucosal regeneration and growth over the ureter, confirming the spontaneous development of a good length neosubmucosal tunnel. All patients demonstrated no evidence of ureteral reflux or ureteral obstruction, whereas an immediate prior cohort of four consecutive patients with bladder capacities < or =30 ml showed that three of four had ureteral reflux (P=0.02) and four of four developed hydronephrosis (P=0.002). All urinary bladders in the present cohort enlarged to expected normal or nearnormal capacities. Serum creatinines were stable throughout the entire follow-up period, with the exception of one patient who had rejection episodes. Two patients had urinary tract infections posttransplantation, but there were no episodes of acute pyelonephritis. CONCLUSIONS: This novel technique for ureteral implantation successfully capitalizes on the regenerative potential of the bladder mucosa, resulting in a physiological, anatomically natural, and very effective neosubmucosal tunnel. It appears to guarantee success against both ureteral reflux and obstruction, no matter how small the urinary bladder, and offers no hindrance to enlarging the bladder to near normal capacity posttransplantation. The implantation technique is simple and safe, and its use should eliminate the reluctance to use these bladders. Moreover, this procedure offers a major incentive for the successful rehabilitation of small, defunctionalized, nonneurogenic bladders after kidney transplantation.

Excellent outcome in recipients of dual kidney transplants: a report of the first 50 dual kidney transplants at Stanford University.

HYPOTHESIS: Recipients of dual kidney transplants from older expanded criteria donors (ECDs) have outcomes similar to recipients of single kidneys from younger donors. Dual transplantation is the use of both adult donor kidneys into a single adult recipient. DESIGN: Donor and recipient variables were entered into a database. Analysis was performed in a retrospective fashion. The unpaired t test and chi2 test were used as appropriate. SETTING: A university teaching hospital. PATIENTS: All adult recipients of cadaveric kidney-only transplants from adult donors between November 1991 and January 1999. Patients were grouped based on whether they received a dual or single transplant and whether the donor was an ECD. The control group of patients received non-ECD cadaveric kidneys. RESULTS: Donors for recipients of dual kidneys were older and had a lower creatinine clearance on hospital admission than recipients of single control kidneys. Recipients of dual transplants were older, had fewer rejections, and had similar 3-month and 1-year serum creatinine levels vs controls. Predictors of an elevated serum creatinine level or graft loss at 3 months in recipients of ECD dual and single transplants included kidneys from donors with unstable preprocurement renal function, and recipients who developed delayed graft function. CONCLUSION: Recipients of dual kidney transplants from ECDs have excellent outcomes similar to recipients of single control kidneys.

The influence of combined trophic factors on the success of fetal pancreas grafts.

BACKGROUND: Fetal pancreas (FP) has the capacity for abundant proliferation and beta cell differentiation. Insulin-like growth factor-1 (IGF-1) promotes FP engraftment in the i.m. site and reversal of diabetes in a rodent model. However, reversal of diabetes by an FP transplant in rats under the influence of IGF-1 is still an inefficient process requiring multiple FP grafts and a prolonged latent period. Numerous other growth and differentiation factors, which include platelet derived growth factor (PDGF), vascular endothelial growth factor, endothelial cell growth factor-alpha and pancreatic islet neogenesis-associated protein, have been implicated in beta cell neogenesis and proliferation. We have analyzed the in vivo role of these growth factors in FP engraftment and reversal of streptozotocin-induced diabetes in rats. METHODS: IGF-1 alone or in combination with other trophic factors was locally administered to eight FP isografts in the thigh muscle of diabetic rats. RESULTS: Diabetes was reversed in a mean of 60+/-26 days in 11 of 11 animals treated with IGF-1. PDGF alone did not promote reversal of diabetes; however, PDGF + IGF-1 resulted in euglycemia in 6 of 6, with a mean of 36+/-14 days (P<0.05). Islet neogenesis-associated protein +IGF-1 resulted in reversal of diabetes in 6 of 6 rats with a mean interval of 50+/-10 days. Vascular endothelial growth factor or endothelial cell growth factor-alpha + IGF-1 provided no advantage compared with IGF-1 alone. CONCLUSIONS: These results demonstrate that IGF-1 is a potent trophic factor for transplanted FP and that PDGF acts synergistically with IGF-1 to promote reversal of diabetes by transplanting FP.

PAH extraction and estimation of plasma flow in human postischemic acute renal failure.

We determined the effect of postischemic injury to the human renal allograft on p-aminohippurate (PAH) extraction (E(PAH)) and renal blood flow. We evaluated renal function in 44 allograft recipients on two occasions: 1-3 h after reperfusion (day 0) and again on postoperative day 7. On day 0 subsets underwent intraoperative determination of renal blood flow (n = 35) by Doppler flow meter and E(PAH) (n = 25) by renal venous assay. Blood flow was also determined in another subset of 16 recipients on postoperative day 7 by phase contrast-cine-magnetic resonance imaging, and E(PAH) was computed from the simultaneous PAH clearance. Glomerular filtration rate (GFR) on day 7 was used to divide subjects into recovering (n = 23) and sustained (n = 21) acute renal failure (ARF) groups, respectively. Despite profound depression of GFR in the sustained ARF group, renal plasma flow was only slightly depressed, averaging 296 +/- 162 ml. min(-1). 1.73 m(-2) on day 0 and 202 +/- 72 ml. min(-1). 1.73 m(-2) on day 7, respectively. These values did not differ from corresponding values in the recovering ARF group: 252 +/- 133 and 280 +/- 109 ml. min(-1). 1.73 m(-2), respectively. E(PAH) was profoundly depressed on day 0, averaging 18 +/- 14 and 10 +/- 7% in recovering and sustained ARF groups, respectively, vs. 86 +/- 6% in normal controls (P < 0.001). Corresponding values on day 7 remained significantly depressed at 65 +/- 20 and 11 +/- 22%, respectively. We conclude that postischemic injury to the renal allograft results in profound impairment of E(PAH) that persists for at least 7 days, even after the onset of recovery. An ensuing reduction in urinary PAH clearance results in a gross underestimate of renal plasma flow, which is close to the normal range in the initiation, maintenance, and recovery stages of this injury.

Dual kidney transplantation: older donors for older recipients.

BACKGROUND: Dual kidney transplantation, the transplantation of both donor kidneys into a single recipient, allows increased use of expanded criteria donors (eg, older donors with a history of hypertension) to alleviate the disparity between available donors and potential recipients. We evaluated outcomes in our dual kidney transplant program that started in 1995. STUDY DESIGN: A retrospective comparison of donor and recipient data between recipients of dual (n = 41) versus single (n = 199) cadaveric renal transplants from February 1, 1995, to March 22, 1998, was performed. Dual kidney transplantation was selectively performed when the calculated donor admission creatinine clearance was less than 90 mL/min and the donor age was greater than 60 years, or if the donor had an elevated terminal serum creatinine. Every attempt was made to age- and size-match the donor and recipients. RESULTS: Recipients of dual kidneys had donors who were older than single kidney donors (59 +/- 12 versus 42 +/- 17 years respectively, p < 0.0001) and had more hypertension (51% versus 29%, p = 0.024). Average urine output was lower in the dual versus single kidney group (252 +/- 157 versus 191 +/- 70 mL/hr, p = 0.036). Donors for dual kidney recipients had a lower donor admission creatinine clearance of 82 +/- 28 mL/min versus 105 +/- 45 mL/min in the single kidney group (p = 0.005). Recipients of dual versus single kidneys were older (58 +/- 11 versus 47 +/- 12 years, p > 0.0001). Dual versus single kidney recipients had similar serum creatinines up to 2 years posttransplant (1.6 +/- 0.3 versus 1.6 +/- 0.7 mg/dL at 2 years, p = NS) and a comparable incidence of delayed graft function (24% versus 33%, p = NS) and 3-month posttransplant creatinine clearance (54 +/- 23 versus 57 +/- 25 mL/min, p = NS). One-year patient and graft survival for single kidney transplantation was 97% and 90%, respectively, and 98% and 89% for dual kidney transplantation (p = NS). CONCLUSIONS: Dual kidney donors were significantly older, had more hypertension, lower urine outputs, and lower donor admission creatinine clearance. Despite these differences, dual kidney recipients had comparable postoperative function, outcomes, and survival versus single kidney recipients. We believe selective use of dual kidney transplantation can provide excellent outcomes to recipients of kidneys from older donors with reduced renal function.

Power Doppler imaging of acute renal transplant rejection.

PURPOSE: We evaluated the usefulness of power Doppler imaging (PDI) in diagnosing acute renal-transplant rejection. METHODS: Twenty-eight patients underwent 33 renal-transplant biopsies for suspected acute rejection. Patterns of renal parenchymal vascularity revealed by PDI in patients with abnormal biopsy results were compared with patterns in a group who had normal biopsy results. PDI examinations were reviewed retrospectively by 2 independent radiologists who had no knowledge of the biopsy results. A PDI diagnosis of acute rejection required marked vascular pruning in both the cortex and medulla. PDI results then were compared with transplant-biopsy results. RESULTS: The sensitivity and specificity of PDI for diagnosing acute renal-transplant rejection were 40% and 100%, respectively. None of the patients with negative biopsy results had PDI abnormalities. The negative predictive value of PDI was 33%, and the positive predictive value was 100%. CONCLUSIONS: In our study, an abnormal sonogram was highly predictive of acute transplant rejection. However, a normal sonogram did not exclude the possibility of rejection.