Magnetic resonance imaging assessment of renal flow distribution patterns during ex vivo normothermic machine perfusion in porcine and human kidneys

Acceptance criteria of deceased donor organs have gradually been extended toward suboptimal quality, posing an urgent need for more objective pre-transplant organ assessment. Ex vivo normothermic machine perfusion (NMP) combined with magnetic resonance imaging (MRI) could assist clinicians in deciding whether a donor kidney is suitable for transplantation. Aim of this study was to characterize the regional distribution of perfusate flow during NMP, to better understand how ex vivo kidney assessment protocols should eventually be designed. Nine porcine and 4 human discarded kidneys underwent 3 h of NMP in an MRI-compatible perfusion setup. Arterial spin labeling scans were performed every 15 min, resulting in perfusion-weighted images that visualize intrarenal flow distribution. At the start of NMP, all kidneys were mainly centrally perfused and it took time for the outer cortex to reach its physiological dominant perfusion state. Calculated corticomedullary ratios based on the perfusion maps reached a physiological range comparable to in vivo observations, but only after 1 to 2 h after the start of NMP. Before that, the functionally important renal cortex appeared severely underperfused. Our findings suggest that early functional NMP quality assessment markers may not reflect actual physiology and should therefore be interpreted with caution

Considerable Variability Among Transplant Nephrologists in Judging Deceased Donor Kidney Offers

Introduction: Transplant clinicians may disagree on whether or not to accept a deceased donor kidney offer. We investigated the interobserver variability between transplant nephrologists regarding organ acceptance and whether the use of a prediction model impacted their decisions.Methods: We developed an observational online survey with 6 real-life cases of deceased donor kidneys offered to a waitlisted recipient. Per case, nephrologists were asked to estimate the risk of adverse outcome and whether they would accept the offer for this patient, or for a patient of their own choice, and how certain they felt. These questions were repeated after revealing the risk of adverse outcome, calculated by a validated prediction model. Results: Sixty Dutch nephrologists completed the survey. The intraclass correlation coefficient of their estimated risk of adverse outcome was poor (0.20, 95% confidence interval [CI] 0.08–0.62). Interobserver agreement of the decision on whether or not to accept the kidney offer was also poor (Fleiss kappa 0.13, 95% CI 0.129–0.130). The acceptance rate before and after providing the outcome of the prediction model was significantly influenced in 2 of 6 cases. Acceptance rates varied considerably among transplant centers. Conclusion: In this study, the estimated risk of adverse outcome and subsequent decision to accept a suboptimal donor kidney varied greatly among transplant nephrologists. The use of a prediction model could influence this decision and may enhance nephrologists’ certainty about their decision.</p

Optimizing utilization and quality assessment of deceased donor kidneys

When patients have end-stage organ failure, organ transplantation is often the best (and sometimes even the only) option. The shortage of donor organs remains a persistent global problem. As deceased donor organs are scarce, it is of great importance that available organs are used optimally. This thesis sheds light on the donation process and kidney utilization of deceased donor kidneys in the Netherlands, clinical decision-making in kidney offers for transplantation, long-term outcomes of kidney preservation methods, and finally it discusses the role of MRI in pre-transplant kidney quality assessment, and in identifying possible complications after transplantation. We concluded that 24% of deceased donor kidneys, that seemed medically suitable in the first place, were not transplanted. Furthermore, we objectified that kidney acceptance is very prone to subjective judgments by doctors, with little consensus on which suboptimal donor kidney should be transplanted or discarded. Finally, we developed a method to visualize intrarenal regional physiological and metabolic processes of a procured kidney on a pump, by several MRI techniques. To conclude, we provide suggestions to improve kidney utilization of deceased donors covering the entire donation cascade, starting during a potential donor’s treatment at the intensive care unit, via a complex sequence of events until eventual transplantation

The correlation between the hemodynamic parameters blood pressure, mean arterial pressure, cardiac index and systemic vascular resistance on serum creatinine in recipients of living donor kidney transplantation

Background: For patients with end-stage renal disease, kidney transplantation is proven to be the best treatment. Within the field of anaesthesiology, hemodynamic parameters are expected to have an impact on the graft function of the transplanted kidney. It is well known that an adequate intra vascular volume is an important indicator for immediate graft function (IGF).17,18 However, intra vascular volume is related to several hemodynamic parameters and it is still relatively uncertain which of those represents best the hemodynamic condition of the patient and the micro circulation of the renal graft. Moreover, in literature most studies contain patient populations in the field of post mortal donors, so even less is known about the hemodynamic state in living donor kidney transplantation (LDKT). This leads to our research question: Is there a correlation between hemodynamic parameters (systolic, diastolic and mean arterial pressure, systemic vascular resistance and cardiac index) and the serum creatinine in the recipient of living donor kidney transplantation? Materials and methods: The study design is an observational prospective cohort pilot. Only patients from the age of 18 were included. Exclusion criteria were right kidney transplantation, a body mass index (BMI) of ≤ 17 or ≥ 35, neurological conditions, altruistic donors and participation in the ABO-incompatible program. In total 23 patients were included. Hemodynamic parameters (systolic, diastolic en mean arterial pressure, systemic vascular resistance and cardiac index) were measured with the PiCCO catheter and a central venous line. Renal function after transplantation was assessed by the serum creatinine. The quantification of the creatinine decline was calculated by 3 different quantification methods (absolute difference, area above the curve and logarithmic decline gradient) over 3 and 9 post-operative days. The investigated hemodynamic time points were: pre-operative, 30 seconds after start reperfusion, 10 minutes after start reperfusion, the average of the entire procedure and the lowest measured value during the entire procedure. Correlation was calculated with Spearman’s correlation coefficient and p<0.05 was considered to be statistically significant. Results: The mean value of serum creatinine before transplantation was 558 μmol/L and 141 μmol/L 9 days after surgery. Regarding 9 days post-operative, the average intra-operative diastolic blood pressure shows a correlation coefficient with a p value of <0,01 in all methods for the quantification of the creatinine. Also the average intra-operative MAP shows significant results among 2 out of 3 methods, with a p value of 0,035 and 0,009. With regard to 3 days post-operative, results show correlation coefficients with significant p values for the average diastolic blood pressure, with p=0,002, p=0,022 and p=0,001. Also the SVR measured 30 seconds after the start of reperfusion shows correlation coefficients with significant p values, with all 3 methods p<0,05. Conclusion: This study shows a correlation between the serum creatinine decline until the 9th postoperative day and the average intra-operative diastolic pressure as well as with the mean arterial pressure. When looking to the serum creatinine decline until the 3rd post-operative day, a correlation is found with the average intra-operative diastolic pressure and the systemic vascular resistance at the moment of 30 seconds after the start of reperfusion

MRI for diagnosis of post-renal transplant complications:current state-of-the-art and future perspectives

Kidney transplantation has developed into a widespread procedure to treat end stage renal failure, with transplantation results improving over the years. Postoperative complications have decreased over the past decades, but are still an important cause of morbidity and mortality. Early accurate diagnosis and treatment is the key to prevent renal allograft impairment or even graft loss. Ideally, a diagnostic tool should be able to detect post-transplant renal dysfunction, differentiate between the different causes and monitor renal function during and after therapeutic interventions. Non-invasive imaging modalities for diagnostic purposes show promising results. Magnetic resonance imaging (MRI) techniques have a number of advantages, such as the lack of ionizing radiation and the possibility to obtain relevant tissue information without contrast, reducing the risk of contrast-induced nephrotoxicity. However, most techniques still lack the specificity to distinguish different types of parenchymal diseases. Despite some promising outcomes, MRI is still barely used in the post-transplantation diagnostic process. The aim of this review is to survey the current literature on the relevance and clinical applicability of diagnostic MRI modalities for the detection of various types of complications after kidney transplantation

A bottom-up approach to model the environmental impact of the last-mile in an urban food-system

Addressing urban consumption and the inherent environmental impacts is considered indispensable for climate change mitigation. However, city-specific insights in urban food-systems are often missing. This study uses a novel bottom-up approach to evaluate the environmental impact of the last-mile of consumers within the food-system. Primary data was gathered by means of a survey (N=663) to model the last-mile, which was combined with secondary data sets, largely from regional studies. Jointly, they informed our hybrid Urban Metabolism - Life Cycle Analysis (UM-LCA) model. This model allowed us to assess the likely environmental impacts of the food-system on global warming, freshwater quality and land use, in relation to urban food consumption behaviour. In our case study, we found that last-mile movements of consumers account for as much as 5.3-5.8 percent of the food-system's total global warming potential. This is a considerable share, especially in proportion to the impact share of all other transport for distribution in the system (11.5-15.6 percent). This is a result of the numerous shopping trips, and while the majority of visits is almost equally shared by motorized and active modes, the vast majority of kilometres for the last-mile is travelled by motorized modes (68.2 percent). Furthermore, interesting differences could be found between city districts in terms of transport modes used by households resulting in different last-mile impacts, which is relevant to explore further for potential policy interventions to stimulate active modes. Food will inevitably get on the urban agenda, and therefore it is important to gain city-specific insights in relation to urban food consumption and its impacts. This study confirms that the influence of consumer choices is considerable and therefore it is worth further mapping these to develop adequate sustainability strategies. We argue that the bottom-up approach provides for both a measuring and monitoring tool, as well as an evaluation tool of urban policy and design towards more sustainable food systems.</p