Borderline kidney graft donors--what are the problems?

Can only histological evaluation determine the allocation of ECD kidneys?

INTRODUCTION

There is a recent debate on the "transplantability" of ECD (Expanded Criteria Donors) kidneys and the selection criteria used to allocate them to single or double transplantation. Remuzzi et al. have defined a protocol incorporating pre-transplant donor biopsy to guide the use of older donor organs. They allocated organs as single or double transplants on the basis of histological findings. We aim to show the pros and cons of the only histological evaluation in the allocation of ECD kidneys, to compare the different experiences in United States and Europe and thus to discuss whether this tool should be used alone or included in a comprehensive clinical and histopathological evaluation.

DISCUSSION

In the United States many Authors stated that the biopsy actually increases the percentage of kidney discarded and they raised questions about the importance of the biopsy in evaluating ECD kidneys for transplantation. On the other hand, the experiences of the majority of european transplant centers showed that allocating kidneys as single or dual transplant based on biopsy findings may achieve good graft and patient outcomes. Moreover, the experience of some centers as ours showed that kidneys allocated as DKT (Dual Kidney Transplant) on the basis of Remuzzi's score could have been suitable for single transplantation suggesting the need of an adjustment of the Remuzzi Score System. Many Authors, who are in favor of histological evaluation, actually believe that a comprehensive clinical and histopathological assessment before transplantation remains necessary. We lack precise national- or international-based selection criteria to guide clinicians. An adjustment of the Remuzzi Score System could be taken into consideration such as narrowing the indication for DKT from those ECD kidneys with higher scores and including the histological evaluation in a multifactor score.

Influence of donor age on renal graft function in first seven post transplant days

Increasing gap between demand and availability of human kidneys for transplantation has forced a re-evaluation of the limits on donor age acceptability. The present study included 74 patients who underwent kidney transplantation in University Clinical Centre Tuzla. In an observational cohort study we assessed impact of donor age on post transplant renal function by analyzing following parameters: 24 hour urine output, creatinine clearance (Cr Cl) and glomerular filtration rate (GFR). Depending on donor age recipients were allocated in to two groups. Group I included patients who received renal graft from donors age up to 55 years, and Group II encountered recipients who received renal graft from donors older than 55 years. Our goal was to determine whether donor age over 55 years significantly diminishes renal graft function in first seven post transplant days. No statistically significant difference was found between Group I and II regarding 24 hour urine output. From second to fifth postoperative day creatinine clearance values were higher in the group of patients who received kidney from donors older than 55 years (47+/-19, 1 vs. 44, 4+/-20, 8). On the fifth, sixth and seventh post operative day GFR was significantly higher in patients who received renal graft from donors age up to 55 years (p<0, 0161). Our data showed no significant difference in observed variables between the two groups, thus indicating that utilization of renal grafts from donors' age > 55 years is acceptable and may considerably expand the donor pool.

The finding of vascular and urinary anomalies in the harvested kidney for transplantation

INTRODUCTION

In kidney transplantation, anatomical vascular and excretory anomalies may represent causes of failure. Today's surgical techniques have made the most of the organs with anatomic anomalies and iatrogenic injury successfully used for transplantation.

MATERIALS AND METHODS

From January 2000 to June 2006, we harvested 230 kidneys, of including 88 kidneys (20%) with vascular, urinary, or vascular-urinary anomalies; 64 kidneys were implanted and 15 were sent to other transplantation centers. Only 9 kidneys were not appropriate for transplantation.

RESULTS

All patients who received kidneys with the above-mentioned anomalies were carefully examined after the transplantation and short-term and long-term complications were evaluated with respect to controls without anomalies.

DISCUSSION

Renal anatomic anomalies are frequently observed during kidney transplantation and may produce postsurgical complications. However, the presence of these anomalies does not necessarily imply the impossibility of using the kidney for a transplant, especially because of improved surgical techniques. Our experience in transplantation procedures showed that even if kidneys present the above-mentioned anomalies they can still be considered appropriate for transplantation when we perform a correct harvesting/back-table transplant surgery. So vascular and urinary anomalies have to be considered always an incentive to research new surgical solutions and to perform a careful surgical technique.

Preferential allocation of marginal kidney allografts to elderly recipients combined with modified immunosuppression gives good results

BACKGROUND

There is an increasing tendency to allocate kidneys from marginal donors in older recipients. This combination optimizes the uses of an expanded donor pool but demands attention for the higher nephrotoxic sensitivity of the kidney and the increased immunosuppression vulnerability of the elderly recipients. We aimed to reduce these hazards by means of a calcineurin-free induction therapy followed by a maintenance regimen targeted to minimize/withdraw steroid.

METHODS

Eighty-eight single (43%) or double (57%) transplant recipients (58.4+/-5.7 years) from 88 marginal donors (67+/-8.3 years) received monoclonal anti-IL-2 receptor antibodies, mycophenolate mofetil (MMF), and steroid. When serum creatinine was less than 2.6 mg/dL, tacrolimus was started and MMF was withdrawn when the tacrolimus trough level was above 15 ng/ml. Steroid was tapered to 5 mg at day 45 and then progressively reduced.

RESULTS

Overall patient and graft survival at the first and fourth year were respectively 100 and 96%, and 98 and 79%. Acute rejection rate was 13.6% (12/88), creatinine clearance remained stable (48.2 ml/min at the sixth month, 50.9 ml/min at 48th month). At the first, second, third, and fourth years, 23, 69, 80, and 100% of recipients were off steroids. For those on steroids, mean dose was respectively 2.6 mg/day from month 12. No recipient re-assumed steroids

CONCLUSIONS

In the "old-for-old" allocation, the calcineurin-inhibitor avoidance at induction and the steroid withdrawal/minimization during the tacrolimus-based maintenance regimen allow a low acute rejection rate, a stable renal function, and favorable recipient and graft outcomes.

Pharmacokinetic Considerations Relating to Tacrolimus Dosing in the Elderly

Relaxation of the upper age limits for solid organ transplantation coupled with improvements in post-transplant survival have resulted in greater numbers of elderly patients receiving immunosuppressant drugs such as tacrolimus. Tacrolimus is a potent agent with a narrow therapeutic window and large inter- and intraindividual pharmacokinetic variability. Numerous physiological changes occur with aging that could potentially affect the pharmacokinetics of tacrolimus and, hence, patient dosage requirements. Tacrolimus is primarily metabolised by cytochrome P450 (CYP) 3A enzymes in the gut wall and liver. It is also a substrate for P-glycoprotein, which counter-transports diffused tacrolimus out of intestinal cells and back into the gut lumen. Age-associated alterations in CYP 3A and P-glycoprotein expression and/or activity, along with liver mass and body composition changes, would be expected to affect the pharmacokinetics of tacrolimus in the elderly. However, interindividual variation in these processes may mask any changes caused by aging. More investigation is needed into the impact aging has on CYP and P-glycoprotein activity and expression. No single-dose, intense blood-sampling study has specifically compared the pharmacokinetics of tacrolimus across different patient age groups. However, five population pharmacokinetic studies, one in kidney, one in bone marrow and three in liver transplant recipients, have investigated age as a co-variate. None found a significant influence for age on tacrolimus bioavailability, volume of distribution or clearance. The number of elderly patients included in each study, however, was not documented and may have been only small. It is likely that inter- and intraindividual pharmacokinetic variability associated with tacrolimus increase in elderly populations. In addition to pharmacokinetic differences, donor organ viability, multiple co-morbidity, polypharmacy and immunological changes need to be considered when using tacrolimus in the elderly. Aging is associated with decreased immunoresponsiveness, a slower body repair process and increased drug adverse effects. Elderly liver and kidney transplant recipients are more likely to develop new-onset diabetes mellitus than younger patients. Elderly transplant recipients exhibit higher mortality from infectious and cardiovascular causes than younger patients but may be less likely to develop acute rejection. Elderly kidney recipients have a higher potential for chronic allograft nephropathy, and a single rejection episode can be more devastating. There is a paucity of information on optimal tacrolimus dosage and target trough concentration in the elderly. The therapeutic window for tacrolimus concentrations may be narrower. Further integrated pharmacokinetic-pharmacodynamic studies of tacrolimus are required. It would appear reasonable, based on current knowledge, to commence tacrolimus at similar doses as those used in younger patients. Maintenance dose requirements over the longer term may be lower in the elderly, but the increased variability in kinetics and the variety of factors that impact on dosage suggest that patient care needs to be based around more frequent monitoring in this age group.

Suboptimal kidney: the experience of a single transplant unit

Not all kidneys are suitable for transplantation. In 2001 in Italy, only 1530 of 1748 organs were transplanted. This difference (-12.5%) not only represents organs harvested from marginal donors considered not suitable, but also kidneys that, although collected from standard donors, had a vascular, parenchymal, or urologic anomaly that made them unsuitable for transplantation. In our center, we established a procedure that defined the characteristics of suboptimal kidneys and allowed us to specifically select the appropriate recipient. We considered as suboptimal all organs with complex arterial anomalies (more than 2 arteries although on a single patch or separated such as to need a double anastomosis or a bench reconstruction); organs with noticeable parenchymal damage (macroscopic sclerosis areas or sutured polar branches accidentally damaged during removal), and organs with complex anomalies of the excretory tract (complete double district). The organs were not considered as suboptimal if they had venous anomalies revised on the bench or if they had a double artery with a single patch <2.5 cm. Such organs were transplanted to recipients who were between 55 and 60 years of age with a body weight of at least 20% less than the donor, and female.

Drug Therapy in Transplant Recipients

Elderly patients with end-stage organ failure are now more frequently undergoing transplantation. Medication management in this population is challenging because of the combination of multiple comorbidities, polypharmacy, and immunological, pharmacokinetic and pharmacodynamic changes attributable to the aging process. Immunosuppressive medications can exacerbate pre-existing medical conditions and promote the development of disease processes. Cardiovascular disorders, such as hypertension, coronary artery disease, congestive heart failure and arrhythmias are common in elderly transplant recipients, and account for most of the deaths in this population. Blood pressure, blood glucose and cholesterol control is of particular concern because elderly transplant recipients frequently have or develop these complications. Elderly transplant recipients are commonly receiving anticoagulation therapy with warfarin and are at a higher risk of bleeding, especially if they have renal dysfunction. Infectious complications occur frequently in the transplanted population, with pneumonia being the most common infection seen in hospitalised patients. Attention to vaccination for the prevention of influenza and pneumococcal infections is important because of the increased risk of these diseases in this population. Depression itself has been associated with decreased survival in older individuals, and depression in elderly transplant recipients may be reversible with the administration of pharmacological agents. Effective long-term care of transplant recipients demands an understanding of how particular medications affect clinical evaluation and treatment. This article addresses some of the practical issues surrounding medication management and prevention of these particular problems in elderly transplant recipients.

Evaluation of the Eurotransplant Senior Program. The results of the first year

On 4 January 1999, the Eurotransplant Senior Program (ESP) was implemented within the Eurotransplant kidney allocation scheme.

PATIENTS AND METHODS

Kidneys obtained from donors aged over 65 years of age (65+) were allocated to a selected group of nonimmunized 65+ patients undergoing their first transplant. All transplants were performed locally to minimize cold-ischemic time. All transplants performed with kidneys from elderly donors that were allocated via ESP (ESP group) were compared to transplants performed with similar kidneys allocated via the standard renal allocation system (control group). Initial kidney function and 1-year graft outcome were assessed.

RESULTS

In 1999, 227 ESP and 102 control transplants were performed. The duration of cold-ischemic time was 12 and 19 h for the ESP and control groups, respectively. No rejection episodes occurred in 60% and 67% of the ESP patients and controls, respectively, while a direct kidney function was observed in 59% of ESP and 49% of control patients. The 1-year graft survival rates, censoring for graft losses due to deaths in patients with functioning grafts, were 86% and 79%, respectively.

CONCLUSION

An old-for-old renal allocation algorithm can be successful provided that risk factors, such as cold-ischemic time, are reduced.