Importance of donor/recipient body weight ratio as a cause of kidney graft loss in the short to medium term

Prediction of early graft function after living donor kidney transplantation by quantifying the "nephron mass" using CT-volumetric software

Early renal function after living-donor kidney transplantation (LDKT) depends on the "nephron mass" in the renal graft. In this study, as a possible donor-recipient size mismatch parameter that directly reflects the "nephron mass," the cortex to recipient weight ratio (CRWR) was calculated by CT-volumetric software, and its ability to predict early graft function was examined. One hundred patients who underwent LDKT were enrolled. Patients were classified into a developmental cohort (n = 79) and a validation cohort (n = 21). Using the developmental cohort, the correlation coefficients between size mismatch parameters, including CRWR, and the posttransplantation estimated glomerular filtration rate (eGFR) were calculated. Multiple regression analysis was conducted to define a formula to predict eGFR 1-month posttransplantation. Using the validation cohort, the validity of the formula was examined. The correlation coefficient was the highest for CRWR (1-month r = 0.66, p < 0.001). By multiple regression analysis, eGFR at 1-month was predicted using the linear model: 0.23 × donor preoperative eGFR + 17.03 × CRWR + 8.96 × preemptive transplantation + 5.10 (adjusted coefficient of determination = 0.54). In most patients in the validation cohort, the observed eGFR was within a 10 ml/min/1.73 m2 margin of the predicted eGFR. CRWR was the strongest parameter to predict early graft function. Predicting renal function using this formula could be useful in clinical application to select proper donors and to avoid unnecessary postoperative medical interventions.

Nonimmunologic Donor-Recipient Pairing, HLA Matching, and Graft Loss in Deceased Donor Kidney Transplantation

Background

In kidney transplantation, nonimmunologic donor-recipient (D-R) pairing is generally not given the same consideration as immunologic matching. The aim of this study was to determine how nonimmunologic D-R pairing relates to independent donor and recipient factors, and to immunologic HLA match for predicting graft loss.

Methods

Seven D-R pairings (race, sex, age, weight, height, cytomegalovirus serostatus, and HLA match) were assessed for their association with the composite outcome of death or kidney graft loss using a Cox regression-based forward stepwise selection model. The best model for predicting graft loss (including nonimmunologic D-R pairings, independent D-R factors, and/or HLA match status) was determined using the Akaike Information Criterion.

Results

Twenty three thousand two hundred sixty two (29.9%) people in the derivation data set and 9892 (29.7%) in the validation data set developed the composite outcome of death or graft loss. A model that included both independent and D-R pairing variables best predicted graft loss. The c-indices for the derivation and validation models were 0.626 and 0.629, respectively. Size mismatch (MM) between donor and recipient (>30 kg [D < R} and >15 cm [D < R]) was associated with poor patient and graft survival even with 0 HLA MM, and conversely, an optimal D-R size pairing mitigated the risk of graft loss seen with 6 HLA MM.

Conclusions

D-R pairing is valuable in predicting patient and graft outcomes after kidney transplant. D-R size matching could offset the benefit and harm seen with 0 and 6 HLA MM, respectively. This is a novel finding.

The impact of donor and recipient weight incompatibility on renal transplant outcomes

BACKGROUND

Donor/recipient size mismatching and correlation to allograft outcome remains poorly defined. This study assessed the impact of donor body weight (DBW) to recipient body weight (RBW) ratio on allograft function and survival.

METHODS

A total of 898 deceased donor renal transplant recipients were included in the study. Patients were divided into quartiles depending on the ratio of DBW/RBW: Q1 (≤ 0.88), Q2 (0.89-1.00), Q3 (1.01-1.22) and Q4 (> 1.22). Donor and recipient characteristics were obtained from the national kidney transplant service database. Serum creatinine and estimated glomerular filtration rate (eGFR) at 1 and 5 years after transplant were compared.

RESULTS

Q4 patients had a higher eGFR 1 year post-transplant (median 59.5 ml/min, IQR 46.8-76.2) compared to Q1-Q3 which had median eGFRs of 54.3, 54.8 and 55.3 ml/min, respectively (p < 0.001). At 5 years post-transplant, there were modest differences in the eGFR across the four quartiles, Q1-4 with median eGFRs of 56.9, 61.1, 61.2 and 58.6 ml/min, respectively (p = 0.02). However, there were no significant differences in 1- and 5-year allograft survival between groups.

CONCLUSIONS

In the setting of deceased donor renal transplantation, mismatching of donor to recipient weight had no impact on 5-year allograft survival, but a low DBW/RBW ratio is modestly associated with lower eGFR.

Influence of Various Living Donor Kidney Measurements in Relation to Recipient Body Measurements on Posttransplant Allograft Functional Outcomes

OBJECTIVES

Donor kidney measurements may affect outcomes of transplanted allografts. We tested allograft and recipient measurements on kidney allograft outcomes. In this study, we compared the effects of kidney allograft volumes, which were measured using computed tomographic angiography before transplant, and allograft weight, which was measured during surgery, in relation to the recipient's body weight and body mass index on kidney function at 6 and 12 months after transplant.

MATERIAL AND METHODS

We included 74 patients (40 female and 34 male patients, mean age of 50.42 ± 9.75 y) in this study.

RESULTS

Intraoperative allograft weight was 182.68 ± 40.33 g (range, 104-266 g). The allograft volume measured using computed tomographic angiography scanning was 123.34 ± 24.26 mL (range, 78-181 mL). The estimated glomerular filtration rates of the recipients at 6 and 12 months after transplant correlated negatively with age and recipient body mass index but correlated positively with allograft volume/recipient body weight, allograft volume/recipient body mass index, allograft weight, allograft weight/recipient body weight, and allograft weight/recipient body mass index values, as concluded by univariate analyses. From multivariate analyses, we found variables of interest presumed to significantly affect the 12-month estimated glomerular filtration rates, including recipient age, allograft volume/recipient body weight, allograft volume/recipient body mass index, allograft weight, allograft weight/recipient body weight, and allograft weight/recipient body mass index.

CONCLUSIONS

Transplanted allograft and recipient body values may be used as predictors of estimated glomerular filtration rates 6 and 12 months after transplant.

A study to evaluate the effect of ratio of donor kidney weight to recipient body weight on renal graft function

AIM AND OBJECTIVES

To study the effect of the ratio of donor kidney weight (dkw) to recipient body weight (rbw) on short and long term graft function in live donor kidney transplant patients.

MATERIALS AND METHODS

It was a prospective study of 79 live donor kidney transplant recipients. Patients were divided into three groups depending on the ratio of dkw in grams to rbw in kilograms. Serum creatinine in milligrams percent on the day of surgery, 7(th) day, 1 month, 6 months, 1 year, and 3 years after the surgery was recorded and their means compared.

RESULTS

The comparison showed that the decrease in mean creatinine level was more in group three patients as compared with group 2 and one patients at 7 days (1.04,1.44 and 1.59 in group 3,2 and 1 respectively) and 30 days (1.12,1.36 and 1.45 in group 3,2 and 1 respectively), showing that higher dkw/rbw ratio is beneficial with respect to the early graft function. However this decrease was not statistically significant (P value -0.256 and 0.358 respectively on 7(th) and 30(th) day). Furthermore long-term function was not different among these three groups.

CONCLUSION

The ratio of dkw to rbw does not have a significant effect on long-term graft function inspite of an early improvement in the function with increased dkw to rbw ratio.

Does donor kidney to recipient body weight ratio influence long-term outcomes of living-donor kidney transplantation?

This study evaluated the effect of the donor kidney to recipient body weight (Kw/Rw) ratio on long-term graft function and survival. We investigated retrospectively whether there was any association between Kw/Rw ratio and long-term graft survival and function after a follow-up of >10 years. We studied a consecutive series of 123 adult-to-adult living kidney transplants. According to the Kw/Rw ratio, patients were divided into 3 groups: "low" (Kw/Rw <2.85; n = 29), "medium" (2.85 ≤ Kw/Rw < 4.04; n = 63), and "high" (≥4.04; n = 31). Among the 3 groups, the mean serum creatinine levels at 1 and 6 months as well as 1 year after transplantation were significantly lower among patients with a high Kw/Rw ratio than in those with a medium or low ratio, but serum creatinine levels at 3 and 5 years did not differ significantly (P = .394 and 0.620, respectively). Graft survival rates at 5 and 10 years after transplantation were significantly lower in the "low" group. We observed a significant association between Kw/Rw ratio and graft survival (P = .018). The Kw/Rw ratio is an important factor for long-term graft survival and early graft function. However, it did not significantly affect subsequent renal function.

Donor kidney adapts to body dimensions of recipient: no influence of donor gender on renal function after transplantation

Female kidneys and kidneys from small donors have been suggested to perform worse after kidney transplantation. Here, we evaluate the impact of gender and body dimensions on posttransplantation GFR in living donor transplantation. Two hundred and ninety-three donor-recipient pairs, who were transplanted at our center were evaluated. All pairs had detailed renal function measurement ((125) I-iothalamate and (131) I-hippuran) 4 months predonation in the donor and 2.5 months posttransplantation in donor and recipient. For 88 pairs, 5 years of recipient follow-up was available. Delta GFR was calculated as (recipient GFR-donor single kidney GFR). Recipients of both male and female kidneys had similar renal function at early and long term after transplantation. Male recipients had higher ERPF, ΔGFR and ΔERPF at both time points. Kidneys of donors smaller than their recipient had higher ΔGFR and ΔERPF than kidneys of larger donors at both time points (p < 0.05). In multivariate analysis, ΔGFR was predicted by donor/recipient BSA-ratio together with transplantation related factors (R(2) 0.19), irrespective of donor and recipient gender. In conclusion, in living donor transplantation, female kidneys perform as well as male donor kidneys. Kidneys adapt to the recipient's body size and demands, independent of gender, without detrimental effects in renal function and outcome up to mid-long term.

Kidney and recipient weight incompatibility reduces long-term graft survival

Long-term function of kidney allografts depends on multiple variables, one of which may be the compatibility in size between the graft and the recipient. Here, we assessed the long-term consequences of the ratio of the weight of the kidney to the weight of the recipient (KwRw ratio) in a multicenter cohort of 1189 patients who received a transplant between 1995 and 2006. The graft filtration rate increased by a mean of 5.74 ml/min between the third and sixth posttransplantation months among patients with a low KwRw ratio (<2.3 g/kg; P<0.0001). In this low KwRw ratio group, the graft filtration rate remained stable between 6 months and 7 years but then decreased at a mean rate of 3.17 ml/min per yr (P<0.0001). In addition, low KwRw ratios conferred greater risk for proteinuria, more antihypertensive drugs, and segmental or global glomerulosclerosis. Moreover, a KwRw ratio<2.3 g/kg associated with a 55% increased risk for transplant failure by 2 years of follow-up. In conclusion, incompatibility between graft and recipient weight is an independent predictor of long-term graft survival, suggesting that avoiding kidney and recipient weight incompatibility may improve late clinical outcome after kidney transplantation.

High weight differences between donor and recipient affect early kidney graft function--a role for enhanced IL-6 signaling

The frequency of delayed function of kidney transplants varies greatly and is associated with quality of graft, donor age and the duration of cold ischemia time. Furthermore, body weight differences between donor and recipient can affect primary graft function, but the underlying mechanism is poorly understood. We transplanted kidney grafts from commensurate body weight (L-WD) or reduced body weight (H-WD) donor rats into syngeneic or allogeneic recipients. Twenty-four hours posttransplantation, serum creatinine levels in H-WD recipients were significantly higher compared to L-WD recipients indicating impaired primary graft function. This was accompanied by upregulation of IL-6 transcription and increased tubular destruction in grafts from H-WD recipients. Using DNA microarray analysis, we detected decreased expression of genes associated with kidney function and an upregulation of other genes such as Cyp3a13, FosL and Trib3. A single application of IL-6 into L-WD recipients is sufficient to impair primary graft function and cause tubular damage, whereas immediate neutralization of IL-6 receptor signaling in H-WD recipients rescued primary graft function with well-preserved kidney graft architecture and a normalized gene expression profile. These findings have strong clinical implication as anti-IL6R treatment of patients receiving grafts from lower-weight donors could be used to improve primary graft function.

The effect of donor/recipient body surface area ratio on outcomes in pediatric kidney transplantation

In pediatric kidney transplantation, the effect of inadequate nephron dosing on graft survival remains undetermined. The aim of this study was to assess the use of D/R BSA, as a reliable indicator of adequate nephron dosing, and eventually a tool to optimize pediatric graft allocation. Following Institutional Review Board approval, we reviewed deceased donor pediatric kidney transplantation (N = 156). We divided patients into three groups, based on D/R BSA: A < or =0.8; B 0.81-1.19; C > or =1.2. Five-yr graft survival rates in the groups were: A 82.0%; B 94.9%; C 97.1% (p = 0.01). Group C had the lowest rate of acute rejection, suggesting a protective effect of increased D/R BSA (group A = 35.7%, group B = 38.9%, group C = 18.8%; p = 0.029). The logistic regression analysis showed that decreased D/R BSA ratio is a risk factor for loss of graft function, at one and five yr [i.e., group A OR 6 (95% CI 1.14-39.30, p = 0.015) and OR 4.49 (95% CI 1.46-13.79, p = 0.009), respectively]. We conclude that for pediatric recipients, D/R BSA is a valuable adjunct when determining long-term graft survival. Its utility may avoid an alloimmune-independent risk factor, increasing the long-term protective value of a good matching policy.

Impact of obesity on renal transplant outcomes

Obesity is a frequent and important consideration to be taken into account when assessing patient suitability for renal transplantation. In addition, posttransplant obesity continues to represent a significant challenge to health care professionals caring for renal transplant recipients. Despite the vast amount of evidence that exists on the effect of pretransplant obesity on renal transplant outcomes, there are still conflicting views regarding whether obese renal transplant recipients have a worse outcome, in terms of short- and long-term graft survival and patient survival, compared with their non-obese counterparts. It is well established that any association of obesity with reduced patient survival in renal transplant recipients is mediated in part by its clustering with traditional cardiovascular risk factors such as hypertension, dyslipidaemia, insulin resistance and posttransplant diabetes mellitus, but what is not understood is what mediates the association of obesity with graft failure. Whether it is the higher incidence of cardiovascular comorbidities jeopardising the graft or factors specific to obesity, such as hyperfiltration and glomerulopathy, that might be implicated, currently remains unknown. It can be concluded, however, that pre- and posttransplant obesity should be targeted as aggressively as the more well-established cardiovascular risk factors in order to optimize long-term renal transplant outcomes.

The effect of donor gender on graft survival

Differences in actuarial graft survival according to donor gender have been reported for renal allografts and for cardiac and hepatic allografts, but for the latter in small series with limited biostatistical power. Using the large database of the Collaborative Transplant Study (CTS), this study is an evaluation of graft survival according to donor and recipient gender for renal (n = 124,911), cardiac (n = 25,432), and hepatic (n = 16,410) transplants. Confounders, such as calendar year, geographical area, race, donor and recipient age, HLA mismatch, cold ischemia time, and others, as well as interaction terms were taken into consideration. Death-censored actuarial renal allograft survival from female compared with male donors was less in female recipients and even more so in male recipients. The donor gender-associated risk ratio for graft loss was 1.15 in female recipients and 1.22 in male recipients. The age-gender interaction term was statistically significant, the gender effect being more pronounced for younger (16 to 45 yr) compared with older (>45 yr) donors. Serum creatinine concentrations 1 yr after transplantation were also higher for recipients with kidney grafts coming from female donors irrespective of recipient gender. For first cardiac transplants, graft survival was inferior when the donor was female and the recipient male, but no statistical difference according to donor gender was demonstrable in female recipients. For first hepatic transplants overall, no significant differences according to donor gender were noted. The proportion of recipients who had treatment for rejection crisis during the first year was higher for male recipients of kidneys from female donors compared with male donors. No difference according to donor gender was demonstrable in female recipients. For cardiac and hepatic grafts, no significant effect of donor gender on the proportion of patients treated for rejection episodes was noted. The data show that adverse effects of female donor gender for different organs is much less uniform than reported in the past. An important confounder is donor age. A gender effect on graft survival is also observed for cardiac allografts. Therefore, in addition to potential "nephron underdosing," further pathomechanisms must play a role, possibly differences in immunogenicity according to donor gender.

Inadequate donor size in cadaver kidney transplantation

There have been conflicting reports that kidneys from small donors may be at increased risk for late graft failure if they are transplanted into large recipients. Data from the United States Renal Data System was used to study all first cadaver kidney transplantations performed during the years 1994 to 1999. Donor and recipient body surface area (BSA) combinations were included along with other patient and transplant characteristics in a Poisson analysis of factors associated with early (in the first 4 mo) and late (> or =4 mo) graft failure. The numbers of large (BSA >2.2 m(2)) and medium size (BSA 1.6 to 2.2 m(2)) recipients that received kidneys from small (BSA <1.6 m(2)) donors are less than expected (chi(2) = 118.09; P < 0.0001), suggesting that transplant centers may be refusing some kidneys on the basis of donor-recipient size differences. Large recipients who received kidneys from small donors made up 1.5% of the population and had a 43% (95% CI, 17 to 75%; P = 0.0004) increased risk of late graft failure compared with medium-size recipients who received kidneys from medium-size donors (53.4% of the population). Medium-size recipients who received kidneys from small donors made up 12.0% of the population and had a 16% (95% CI, 6 to 26%; P = 0.0012) increased risk of late graft failure. Disparities in recipient and donor size had similar adverse affects on mortality. Effects of recipient obesity (body mass index) and donor gender on late graft survival were no longer statistically significant after the effects of donor and recipient body size were taken into account. In conclusion, the relative size of the donor and recipient should possibly be taken into account when choosing kidneys for transplantation.

Evidence that the ratio of donor kidney weight to recipient body weight, donor age, and episodes of acute rejection correlate independently with live-donor graft function

BACKGROUND

We demonstrated that higher donor kidney weight-to-recipient body weight (KW/BW) ratio showed better graft function in acute rejection-free renal recipients.

METHODS

We investigated the impacts of KW/BW ratios on the graft function including acute rejection and donor's age in 259 live-donor renal recipients. Renal parameters were measured yearly. Correlations between the variables and each parameter were assessed by mixed regression and analysis of variance.

RESULTS

Renal function showed a positive correlation with the KW/BW ratio, but an inverse correlation with the rejection episodes and donor's age. The regression slope for serum creatinine or creatinine clearance by these covariants was consistent each year. On comparing the lower KW/BW ratios (<3.0) with higher ratios (> or =4.5), the higher was associated with better graft function. Increased donor's age was associated with worse graft function.

CONCLUSIONS

KW/BW ratio, donor's age, and the number of acute rejections are independent covariants for graft function.

Influence of allograft size to recipient body-weight ratio on the long-term outcome of renal transplantation

BACKGROUND

The critical nephron mass needed to meet the metabolic demands of an individual depends on the body-weight. This study evaluated the effect of the kidney transplant ultrasonographic size to recipient body-weight ratio (Tx/W) on the outcome of kidney transplantation.

METHODS

A consecutive series of 104 cadaveric renal transplants was studied. Transplant cross-sectional area (TXSA) was measured ultrasonographically in the first week after transplantation as an index of renal size. A 'nephron dose' index (Tx/W) was calculated by dividing TXSA by recipient weight and was used to define three groups of patients, with high (more than 0.45), medium (0.3-0.45) or low (less than 0.3) Tx/W ratios. Isotope glomerular filtration rate (GFR) measurements were made at 1, 6 and 12 months after transplantation.

RESULTS

The serum creatinine level was significantly lower in the first 5 years after transplantation in patients with a high Tx/W ratio than in those with a medium or low ratio. GFR measurements were marginally higher in the groups with a high and medium Tx/W ratio compared with the low Tx/W group. A statistically significant association between Tx/W ratio and graft survival was not found.

CONCLUSION

The renal transplant size to recipient weight ratio was an important determinant of long-term renal allograft function in this study. Extreme mismatching between allograft and recipient size should be avoided where possible, but the findings presented require confirmation in larger studies before clear recommendations can be made about size matching and kidney allocation.

Early immunologic and nonimmunologic predictors of arterial hypertension after renal transplantation

We followed up a cohort of 680 renal transplant recipients receiving cyclosporine (CsA) immunosuppression with the aim of establishing an early-risk profile for early and late hypertension (HT) after renal transplantation (RTx), specifically comparing the predictive role of immunologic and nonimmunologic markers of graft prognosis. HT was defined as the need for antihypertensive drugs. The prevalence of HT was 65% at the time of RTx, increased to a peak of 78% at the end of the first year, and stabilized between 71% and 73% thereafter. Multivariate analysis identified HT at the time of RTx, basal renal disease, and grafting the right kidney as independent predictors of HT 3 months after RTx. The risk profile for HT 12 months after RTx included HT present at RTx, grafting the right kidney, markers of early ischemia-reperfusion injury (delayed graft function, cold and warm ischemia), and transplant from an elderly or female donor. Polytransfusion before RTx was associated with a decreased risk for HT, but retransplantation, increased reactivity against the lymphocyte panel, poor HLA compatibility, and early acute rejection did not portend an increased risk for the complication under study. The CsA schedule (dose, trough levels) correlated poorly with the blood pressure status of the patients, but simultaneous graft function was independently associated with late HT. In conclusion, the early predictive profile for HT after RTx includes, preferentially, nonimmunologic markers of graft prognosis. Hyperfiltration damage may be a significant pathogenic mechanism for this complication of RTx.

Renal transplantation with limit donors: to what should the good results obtained be attributed?

BACKGROUND

With the aim of offsetting the reduction in donors of kidneys for transplantation, we extended the acceptance criteria, considering donors over 60 years old.

METHODS

The results obtained in 84 transplants carried out with this type of donor (group A) was compared with those of a control group of 125 transplants carried out with kidneys from donors under 60 years old (group B). The protocol for selection of donors was appropriate creatinine clearance, minimum proteinuria, and normal renal scan. The histological study was not included because it was not considered appropriate to assess the extent of the possible glomerulosclerosis, as this has a focal, segmented distribution. There were no significant differences between the recipients except for age (57.8 years old in group A vs. 39.2 years in group B).

RESULTS

After the transplantation, there were significant differences in the duration of hospitalization (26.8 days vs. 21.8 days, P<0.009), annual plasma creatinemia (177, 225, 233, 235, and 205 micromol/L vs. 136, 150, 121, 111, and 133 micromol/L, P<0.0002/0.0004), graft survival (87%, 85%, 81%, 81%, and 81% vs. 89%, 88%, 86%, 86%, and 85%, P<0.03), and patient survival (92%, 89%, 85%, 85%, and 85% vs. 99%, 99%, 97%, 96%, and 95%, P<0.0004). Death of the patient was the only significantly more frequent cause of graft loss among group A patients (7 vs. 1 death, P<0.004). No kidney was "never working" and none were lost because of chronic rejection.

CONCLUSIONS

It was concluded that elderly donors should be considered as suitable for transplantation irrespective of their chronological age, provided that they fulfill the acceptance criteria. The quality of life achieved was comparable in both groups. Despite the lower renal function in group A, this remained constant during the follow-up period.