Prognostic significance of microvascular thrombosis in donor kidney allograft biopsies

Incidence, Nature and Natural History of Additional Histological Findings in Preimplantation and Implantation Kidney Transplant Biopsies

The quality assurance provided by preimplantation biopsy quantification of chronic damage may allow greater use of kidneys from expanded criteria donors, and thereby expand the deceased donor pool. Preimplantation biopsy may, however, identify additional acute or chronic pathologies not considered in the scoring of chronic damage, and these may influence the decision to implant or discard the kidney. This single-centre retrospective cohort study of a contemporary UK donor population systematically characterised the nature of additional findings in 1,046 preimplantation and implantation biopsies over an eight-year period. A diverse range of findings were identified in 111/1,046 (11%) organs; most frequently diabetic glomerulopathy, focal segmental glomerulosclerosis, (micro)thrombi, neutrophil casts, and immunoglobulin/complement staining. Seventy (63%) of these were transplanted, with subsequent biopsy in 41 (58%) cases confirming that 80% of the initial acute changes had spontaneously resolved, while there was no progression of diabetic glomerulopathy, and the lesions of focal segmental glomerulosclerosis were not identified. Over 75% of assessable grafts with additional histological findings at the time of transplant showed adequate function at one-year following transplant. In conclusion, most histological abnormalities that may be identified in addition to chronic scarring in preimplantation kidney biopsies would not preclude transplantation nor predict poor graft function.

Successful Utilization of Kidney Allografts with Diffuse Glomerular Fibrin Thrombi on the Preimplantation Biopsy after Circulatory Death: A Case Series

Background: Kidney allografts with the presence of diffuse glomerular fibrin thrombi are typically rejected by most centers due to concern for poor allograft outcomes in the recipients. The aim of this study was to report our single center experience in the use of such deceased donor allografts. Methods: Retrospective single-center cohort study of kidney transplant recipients who received deceased donor allografts with moderate-to-severe diffuse glomerular fibrin microthrombi on the pre-implantation biopsy. Results: Three adult recipients received deceased donor kidney transplantation from donation after circulatory death donors. One patient was pre-emptive to dialysis at the time of transplant. The donors had moderate-to-severe diffuse glomerular fibrin thrombi on preimplantation biopsies with no evidence of cortical necrosis. Mean follow-up period was 196 days. None of the recipients developed delayed allograft function. The mean 3-month and 6-month creatinine were 1.6 and 1.5 mg/dL, respectively, with corresponding mean eGFRs (estimated glomerular filtration rates) of 45.7 and 47.3 mL/min/1.73m2. Conclusions: After excluding significant cortical necrosis by experienced transplant renal pathologist, otherwise transplantable kidney allografts with diffuse fibrin thrombi may be successfully transplanted in renal transplant recipients with good renal outcomes.

Novel Ex-Vivo Thrombolytic Reconditioning of Kidneys Retrieved 4 to 5 Hours After Circulatory Death

BACKGROUND

Due to organ shortage, many patients do not receive donor organs. The present novel thrombolytic technique utilizes organs from donors with uncontrolled donation after circulatory deaths (uDCD), with up to 4-5 h warm ischemia, without advanced cardiopulmonary resuscitation (aCPR) or extracorporeal circulation (EC) after death.

METHODS

The study group of pigs (n = 21) underwent simulated circulatory death. After 2 h, an ice slush was inserted into the abdomen. Kidneys were retrieved 4.5 h after death. Lys-plasminogen, antithrombin-III (ATIII), and alteplase (tPA) were injected through the renal arteries on the back table. Subsequent ex vivo perfusion at 15 °C was continued for 3 h, followed by 3 h with red blood cells (RBCs) at 32 °C. Perfusion outcome and histology were compared between uDCD kidneys, receiving no thrombolytic treatment (n = 8), and live donor kidneys (n = 7). The study kidneys were then transplanted into pigs as autologous grafts with a single functioning autologous kidney as the only renal support. uDCD control pigs (n = 8), receiving no ex vivo perfusion, served as controls.

RESULTS

Vascular resistance decreased to <200 mmHg/mL/min ( P < 0.0023) and arterial flow increased to >100 mL/100 g/min ( P < 0.00019) compared to controls. In total 13/21 study pigs survived for >10 days, while all uDCD control pigs died. Histology was preserved after reconditioning, and the creatinine level after 10 days was next to normal.

CONCLUSIONS

Kidneys from extended uDCD, not receiving aCPR/EC, can be salvaged using thrombolytic treatment to remove fibrin thrombi while preserving histology and enabling transplantation with a clinically acceptable early function.

Ex-vivo Kidney Machine Perfusion: Therapeutic Potential

Kidney transplantation remains the gold standard treatment for patients suffering from end-stage kidney disease. To meet the constantly growing organ demands grafts donated after circulatory death (DCD) or retrieved from extended criteria donors (ECD) are increasingly utilized. Not surprisingly, usage of those organs is challenging due to their susceptibility to ischemia-reperfusion injury, high immunogenicity, and demanding immune regulation after implantation. Lately, a lot of effort has been put into improvement of kidney preservation strategies. After demonstrating a definite advantage over static cold storage in reduction of delayed graft function rates in randomized-controlled clinical trials, hypothermic machine perfusion has already found its place in clinical practice of kidney transplantation. Nevertheless, an active investigation of perfusion variables, such as temperature (normothermic or subnormothermic), oxygen supply and perfusate composition, is already bringing evidence that ex-vivo machine perfusion has a potential not only to maintain kidney viability, but also serve as a platform for organ conditioning, targeted treatment and even improve its quality. Many different therapies, including pharmacological agents, gene therapy, mesenchymal stromal cells, or nanoparticles (NPs), have been successfully delivered directly to the kidney during ex-vivo machine perfusion in experimental models, making a big step toward achievement of two main goals in transplant surgery: minimization of graft ischemia-reperfusion injury and reduction of immunogenicity (or even reaching tolerance). In this comprehensive review current state of evidence regarding ex-vivo kidney machine perfusion and its capacity in kidney graft treatment is presented. Moreover, challenges in application of these novel techniques in clinical practice are discussed.

Aggravation of fibrin deposition and microthrombus formation within the graft during kidney transplantation

In kidney transplantation, microthrombi and fibrin deposition may lead to local perfusion disorders and subsequently poor initial graft function. Microthrombi are often regarded as donor-derived. However, the incidence, time of development, and potential difference between living donor kidneys (LDK) and deceased donor kidneys(DDK), remains unclear. Two open-needle biopsies, taken at preimplantation and after reperfusion, were obtained from 17 LDK and 28 DDK transplanted between 2005 and 2008. Paraffin-embedded sections were immunohistochemically stained with anti-fibrinogen antibody. Fibrin deposition intensity in peritubular capillaries(PTC) and glomeruli was categorized as negative, weak, moderate or strong and the number of microthrombi/mm² was quantified. Reperfusion biopsies showed more fibrin deposition (20% to 100% moderate/strong, p < 0.001) and more microthrombi/mm² (0.97 ± 1.12 vs. 0.28 ± 0.53, p < 0.01) than preimplantation biopsies. In addition, more microthrombi/mm² (0.38 ± 0.61 vs. 0.09 ± 0.22, p = 0.02) and stronger fibrin intensity in glomeruli (28% vs. 0%, p < 0.01) and PTC (14% vs. 0%, p = 0.02) were observed in preimplantation DDK than LDK biopsies. After reperfusion, microthrombi/mm² were comparable (p = 0.23) for LDK (0.09 ± 0.22 to 0.76 ± 0.49, p = 0.03) and DDK (0.38 ± 0.61 to 0.90 ± 1.11, p = 0.07). Upon reperfusion, there is an aggravation of microthrombus formation and fibrin deposition within the graft. The prominent increase of microthrombi in LDK indicates that they are not merely donor-derived.

Potentiating Renal Regeneration Using Mesenchymal Stem Cells

BACKGROUND

The potential of a mesenchymal stem cell (MSC) therapy to accelerate the repair of ischemically damaged human kidneys during 24 hours of warm perfusion was evaluated. The hypothesis was that by administering MSC directly to the renal tissue, there would be an improved opportunity for cellular repair mediated by intrarenal paracrine effects.

METHODS

Studies were performed using the exsanguinous metabolic support (EMS) tissue-engineering platform. Five pairs of human kidney allografts from donation after circulatory death donors were studied. One human kidney was EMS perfused for 24 hours (control), whereas its paired kidney was EMS perfused with MSC (1 × 10). The kidneys were evaluated for DNA synthesis, cytokine/chemokine synthesis, cytoskeletal regeneration, and mitosis.

RESULTS

Treatment with MSC resulted in reduced inflammatory cytokines synthesized by the kidneys. Mesenchymal stem cell treatment led to a significant increase in the synthesis of adenosine triphosphate and growth factors resulting in normalization of metabolism and the cytoskeleton. Toluidine Blue staining of MSC-treated kidneys demonstrated a significant increase in the number of renal cells undergoing mitosis (26%) compared with EMS perfusion alone.

CONCLUSIONS

To our knowledge, our work is the first to have demonstrated actual renal regeneration while ischemically damaged human kidneys are perfused ex vivo for 24 hours. The observed regeneration entails: increased synthesis of adenosine triphosphate, a reduced inflammatory response, increased synthesis of growth factors, normalization of the cytoskeleton and mitosis. The ability to regenerate renal tissue ex vivo sufficiently to result in immediate function could revolutionize transplantation by solving the chronic organ shortage.

No impact of disseminated intravascular coagulation in kidney donors on long-term kidney transplantation outcome: A multicenter propensity-matched study

The diagnosis of disseminated intravascular coagulation (DIC) is often considered to be a contraindication to organ donation. The aim of this study was to evaluate the impact of DIC+ donors on kidney recipient (KR) evolution. We identified 169 KRs with DIC+ donation after brain death donors between January 1996 and December 2012 in 6 French transplant centers. Individuals were matched using propensity scores to 338 recipients with DIC- donors according to donor age and sex, whether expanded criteria for the donor existed, graft year, and transplantation center. After kidney transplantation, delayed graft function was observed in 28.1% of DIC+ KRs and in 22.8% of DIC- KRs (NS). Renal allograft survival at 1, 5, and 10 years was 94.5%, 89.3%, and 73.9% and 96.2%, 90.8%, and 81.3% in DIC+ KRs and DIC- KRs, respectively (NS). The median estimated glomerular filtration rate (eGFR) was similar between DIC+ and DIC- KRs at 3 months, 1 year, and 10 years: 45.9 vs 48.1 mL/min, 42.1 vs 43.1 mL/min, and 33.9 vs 38.1 mL/min, respectively. Delayed calcineurin inhibitor introduction or induction had no impact on delayed graft function rate or eGFR evolution at 10 years after transplantation in DIC+ KRs. Donor DIC did not seem to affect initial outcome, long-term graft function, or allograft survival.

Innate networking: Thrombotic microangiopathy, the activation of coagulation and complement in the sensitized kidney transplant recipient

Thrombotic microangiopathy (TMA) is a histological feature of antibody-mediated rejection and has the potential to cause problematic graft dysfunction, particularly for highly sensitized cross-match positive kidney transplant recipients. Prompt recognition of pertinent histopathological and systemic features of TMA in kidney transplantation is necessary. Underlying mechanisms of this process involve the activation of both complement and coagulation systems as a response to HLA antibody. As serine proteases, coagulation and complement cascades exhibit similar characteristics with respect to homeostatic function. Increasing evidence now exists for the interaction between these innate defenses in both activation and regulation, lending scope for intervention. Understanding the complexities of these interactions remains a challenge. This review provides an overview of the current understanding, particularly with respect to the activation of coagulation and complement by HLA antibody in the setting of highly sensitized kidney transplantation.

Fibrin thrombi in deceased donor kidneys: Prevalence and influence on graft function and graft survival in transplanted patients

Fibrin thrombi (FT) are occasionally found in the pre-implantation biopsy of kidneys from deceased donors. The aim of this study was to monitor the prevalence and answer the question whether FT has any impact on future graft function in a Danish patient cohort. We looked for FT in all donor kidney biopsies taken at the time of renal transplantation in a Danish transplantation unit during a 10-year period. Every recipient transplanted with a FT donor kidney (n = 15) were matched with up to five control recipients (n = 69), and graft function and graft survival were assessed. FT was present in 3% of the transplanted donor kidneys. Graft function was reduced in the FT group 6 months after transplantation (median estimated glomerular filtration rate (eGFR): 29 mL/min vs 46 mL/min; p = 0.017), but at 12 months, an apparent difference did not reach statistical significance. More patients were on dialysis in the FT group after 12 months compared with the control group (27% vs 6%; p = 0.049). In conclusion, FT in donor kidney biopsies at time of transplantation is a risk factor for the development of reduced renal function during the first year of transplantation.

Rapid Resolution of Donor-Derived Glomerular Fibrin Thrombi After Deceased Donor Kidney Transplantation

The aim of this study was to determine the clinical and histologic outcomes related to transplanting kidneys from deceased donors with glomerular fibrin thrombi (GFT). We included all cases transplanted between October 2003 and October 2014 that had either a preimplantation biopsy or an immediate postreperfusion biopsy showing GFT. The study cohort included 61 recipients (9.9%) with GFT and 557 in the control group without GFT. Delayed graft function occurred in 49% of the GFT group and 39% in the control group (p = 0.14). Serum creatinine at 1, 4, and 12 months and estimated GFR at 12 months were similar in the two groups. Estimated 1-year graft survival was 93.2% in the GFT group and 95.1% in the control group (p = 0.22 by log-rank). Fifty-two of the 61 patients in the GFT group (85%) had a 1-month protocol biopsy, and only two biopsies (4%) showed residual focal glomerular thrombi. At the 1-year protocol biopsy, the prevalence of moderate to severe interstitial fibrosis and tubular atrophy was 24% in the GFT group and 30% in the control group (p = 0.42). We concluded that GFT resolves rapidly after transplantation and that transplanting selected kidneys from deceased donors with GFT is a safe practice.

Enhancing kidney function with thrombolytic therapy following donation after cardiac death: a multicenter quasi-blinded prospective randomized trial

Kidneys from donors after cardiac death (DCD) are at risk for inferior outcomes, possibly due to microthrombi and additional warm ischemia. We describe an organ procurement organization-wide trial utilizing thrombolytic tissue plasminogen activator (tPA) during machine pulsatile perfusion (MPP). A kidney from each recovered kidney pair was prospectively randomized to receive tPA (50 mg Alteplase) or no tPA (control) in the MPP perfusate. From 2011 to 2013, 24 kidneys were placed with enrolled recipients from 19 DCD kidney donors. There were no significant differences for absolute values of flow or resistance while undergoing MPP between the groups, nor rates of achieving discrete flow and resistance targets. While there was a trend toward lower creatinine and higher glomerular filtration rates in the tPA group at 3, 6, 9, and 12 months, these differences were not significant. Delayed graft function (DGF) rates were 41.7% in the tPA group vs. 58.4% in the control group (OR 0.51, 95%CI 0.10-2.59, p = 0.68). Death-censored graft survival was similar between the groups. In this pilot study, encouraging trends are seen in kidney allograft function independent of MPP parameters following DCD kidney transplantation for those kidneys receiving thrombolytic tPA and MPP, compared with standard MPP.

Donor kidney microthrombi and outcomes of kidney transplant: a single-center experience

The kidney wait list has outgrown the supply of available organs every year. Efforts are being made to minimize discard rate of organs. One such area is the use of kidneys with glomerular microthrombi (MT). We retrospectively examined graft/patient outcomes in 28 cases with MT in pre-implantation biopsies. All patients had follow-up of at least 36 months, or until graft loss or death. In total, 17 of the 18 patients who underwent follow-up biopsy within 90 days of transplantation had cleared all MT. Most patients had excellent long-term graft function. On a closer review of the biopsies included in our study, we found that even in the organs with the most widespread thrombosis, the median percentage of glomeruli with more than 50 percentage of the capillary loops occluded was 8% (range 0-17%). The current practice of mentioning the % of glomeruli with thrombi cannot adequately capture the extent of donor organ pathology, as the actual % glomerular area involved can vary greatly from case to case. Future studies should attempt to quantify donor thrombi by a more robust method and revisit the issue of using clinico-pathologic parameters to predict allograft function in the setting of MT.

Exploring associations between anthropometric indices and graft function in patients receiving renal transplant

BACKGROUND

The aim of the present study was to identify indicators of malnutrition, as obtained by anthropometric measurements, that might be potential predictors of transplant outcomes.

METHODS

One hundred and three patients receiving a graft from a living or a deceased donor were included in this prospective study. Body mass index (BMI) based on pretransplant dry body weight, triceps skinfold, mid-arm muscle circumference and corrected mid-arm muscle area were measured. Post-transplant data on delayed graft function (DGF) and glomerular filtration rate (GFR) at discharge were collected until patient discharge.

RESULTS

Delayed graft function developed in 36.9% of the patients. BMI was the only anthropometric variable associated with a higher likelihood of DGF (odds ratio = 1.25, 95% confidence interval = 1.07-1.47) after adjusting for age, gender, donor group, donor age and years of dialysis before transplantation. Obesity was associated with a higher frequency of DGF (83.3% versus 31.1%, P = 0.001) compared to normal weight. GFR at discharge was negatively associated with BMI [β = -0.014 (0.005), P = 0.004], being overweight [β = -0.151 (0.041), P < 0.001] and obesity [β = -0.188 (0.053), P = 0.001], after adjusting for age, gender, donor group, donor age and years of dialysis, but was not associated with indices of muscle reserves.

CONCLUSIONS

The likelihood of DGF was higher among obese patients, whereas GFR at discharge was negatively associated with being overweight and obesity.

Donor Kidney Evaluation

In patients with end-stage renal disease, kidney transplantation is the best means to extend survival and offer a better quality of life. The current shortage of organs available for transplantation has led to an effort to expand the kidney donor pool, including the use of nonideal donor kidneys. Assessment of the quality of the donated kidney is essential, and would facilitate the decision to transplant a potential organ or discard it. Multiple clinical and histologic parameters have been examined to evaluate the donor kidney and relate the findings to the graft outcome, but clear-cut criteria are yet to be defined.

Successful renal transplantation from a brain-dead deceased donor with head injury, disseminated intravascular coagulation and deranged renal functions

Deceased donors (DDs) with the brain death due to head injury are the major source of organs for transplantation. The incidence of post-head injury disseminated intravascular coagulation (DIC) ranges from 24% to 50%. Many centers do not accept organs from donors with DIC due to increased risk of primary graft non-function and/or high chances of morbidity/mortality. We performed two successful renal transplants from a DD with head injury with DIC and deranged renal function. One of the recipients developed transient thrombocytopenia, but there was no evidence of DIC or delayed graft functions in either of the recipients. Over a follow-up of 1 month, both are doing well with stable graft function and hematological profile. Thus, a carefully selected DD with severe DIC even with deranged renal function is not a contraindication for organ donation if other risk factors for primary non-function are excluded. This approach will also help in overcoming organ shortage.

Implications of donor disseminated intravascular coagulation on kidney allograft recipients

BACKGROUND AND OBJECTIVES

Disseminated intravascular coagulation (DIC) is common in deceased kidney donors and is considered a relative contraindication to donation. The significance of donor DIC on recipient kidney function is poorly understood. Additionally, the significance of thrombocytopenia in recipients of kidneys from DIC-positive donors is understudied.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In a retrospective cohort of 162 kidney transplants, the presence of DIC in donors, the occurrence of thrombocytopenia in recipients, and risk factors for delayed or slow graft function (DGF/SGF) were assessed. The effects of DIC donor status on DGF/SGF in the study sample as a whole, and of thrombocytopenia on DGF/SGF in recipients of DIC-positive kidneys specifically, were examined using multiple logistic regression.

RESULTS

DIC donor status was not associated with occurrence of DGF/SGF, but thrombocytopenia was significantly associated with DIC-positive donor status (P=0.008). Thrombocytopenia was independently associated with DGF/SGF only in the recipients of DIC-positive kidneys (P=0.005). Patient and graft survival at 1 year were not affected by donor DIC status or by thrombocytopenia status.

CONCLUSIONS

Donor DIC was not associated with short-term suboptimal graft function, defined as DGF/SGF, nor with long-term patient or graft survival. However, thrombocytopenia appears to portend DGF/SGF in recipients of DIC-positive kidneys and may be a clinical sign on which the basis of therapeutic decisions could be undertaken.

Higher recipient body mass index is associated with post-transplant delayed kidney graft function

To examine whether a higher body mass index (BMI) in kidney recipients is associated with delayed graft function (DGF), we analyzed data from 11,836 hemodialysis patients in the Scientific Registry of Transplant Recipients who underwent kidney transplantation. The patient cohort included women, blacks, and diabetics; the average age was 49 years; and the mean BMI was 26.8 kg/m(2). After adjusting for relevant covariates, multivariate logistic regression analyses found that one standard deviation increase in pretransplant BMI was associated with a higher risk of DGF (odds ratio (OR) 1.35). Compared with patients with a pretransplant BMI of 22-24.99 kg/m(2), overweight patients (BMI 25-29.99 kg/m(2)), mild obesity patients (BMI 30-34.99 kg/m(2)), and moderate-to-severe obesity patients (BMI 35 kg/m(2) and over) had a significantly higher risk of DGF, with ORs of 1.30, 1.42, and 2.18, respectively. Similar associations were found in all subgroups of patients. Hence, pretransplant overweight or obesity is associated with an incrementally higher risk of DGF.

Significance of microvascular thrombosis in renal allografts: role of ex vivo thrombolytic therapy

BACKGROUND

Microvascular thrombosis is an uncommon pathologic finding in cadaveric kidneys. It is associated with disseminated intravascular coagulation most frequently associated with head injuries and massive blood transfusions. The high rate of non-function published in the literature portends an ominous significance for transplanted organs, which have been discarded by many transplant centers.

METHODS

In this report, we document the effectiveness of ex vivo thrombolytic therapy with activase, a plasminogen activator, injected intra-arterially in 12 kidneys with extensive histologic intraglomerular microvascular thrombosis prior to transplantation. All cold stored cadaveric kidneys were flushed for 50 min with 50 mg of activase diluted in University of Wisconsin solution. Pre-flush and post-flush wedge biopsies were performed on the allografts.

RESULTS

All biopsies showed complete resolution of the intraglomerular microthrombi following activase flush. One kidney clotted in the third week. Three patients developed delayed graft function (25%) of which one experienced allograft thrombosis following one month after transplantation. All remaining grafts are still functioning at a mean follow up of 55.1 months (range: 23-71) with a mean serum creatinine of 1.8 mg/dL (range: 0.8-2.5).

CONCLUSIONS

Back table flush with activase rapidly lyses severe intraglomerular microthrombi making them successfully transplantable. Pre-treatment with activase seems to be an effective therapeutic intervention for kidneys with massive intraglomerular thrombosis.

Delayed graft function in renal transplantation

PURPOSE OF REVIEW

Delayed graft function is an important determinant of patient and graft survival. A complex of pathologic mechanisms intervenes in the pathophysiology of this outcome. This paper reviews the main processes involved in delayed graft function as they relate to five chronologically related stages: donor tissue quality, brain death and related stress, preservation variables, immune factors, and recipient variables.

RECENT FINDINGS

Dialyzed delayed graft function and nondialyzed slow graft function both have a negative impact on graft survival and on the incidence of acute rejection. Expanded-criteria donors, older donors, and non-heart-beating donors are more frequently used. The long-term results of the use of well-selected non-heart-beating donors are surprisingly good. The process of ischemia/reperfusion injury is already initiated in the brain-death donor and continues during preservation of the graft. Graft-infiltrating T cells, heat shock proteins, and heme oxygenase-1 are implicated in the process. Modifications in immunosuppressive therapy and pharmacologic modulations have an effect on delayed graft function. Delayed graft function plays a part in the incidence of acute rejection, impaired graft function, and survival of patients and grafts.

SUMMARY

This review discusses the current literature on several recent findings of pathophysiologic mechanisms of, and possible therapeutic interventions in, delayed graft function.

Disseminated intravascular coagulation (DIC) in a kidney donor associated with transient recipient DIC

It has been controversial whether or not to accept kidneys for transplantation from donors with disseminated intravascular coagulation (DIC). We report two recipients who received the kidneys from a donor with DIC following traumatic head injury. Despite evidence of donor kidney glomerular fibrin deposits and ongoing low-grade DIC in the recipients, which resolved after 5-7 days; both recipients did well suggesting that donors with DIC can be successfully used for renal transplantation.