Isometric Tubular Epithelial Vacuolization in Renal Allograft Biopsy Specimens of Patients Receiving Low-Dose Intravenous Immunoglobulin for a Positive Crossmatch

Synthetic hemoglobin-based oxygen carriers are an acceptable alternative for packed red blood cells in normothermic kidney perfusion

Normothermic machine perfusion presents a novel platform for pretransplant assessment and reconditioning of kidney grafts. Maintaining the metabolic activity of a preserved graft at physiologic levels requires an adequate oxygen supply, typically delivered by crystalloid solutions supplemented with red blood cells. In this study, we explored the feasibility of using a synthetic hemoglobin-based oxygen carrier (HBOC) in human kidney normothermic perfusion. Fourteen discarded human kidneys were perfused for 6 hours at a mean temperature of 37°C using a pressure-controlled system. Kidneys were perfused with a perfusion solution supplemented with either HBOC (n = 7) or packed red blood cells (PRBC) (n = 7) to increase oxygen-carrying capacity. Renal artery resistance, oxygen extraction, metabolic activity, energy stores, and histological features were evaluated. Throughout perfusion, kidneys from both groups exhibited comparable behavior regarding vascular flow (P = .66), oxygen consumption (P = .88), and reconstitution of tissue adenosine triphosphate (P = .057). Lactic acid levels were significantly higher in kidneys perfused with PRBC (P = .007). Histological findings were comparable between groups, and there was no evidence of histological damage caused by the HBOC. This feasibility experiment demonstrates that a HBOC solution can offer a logistically more convenient off-the-shelf alternative to PRBC in normothermic machine perfusion of human kidneys.

Pathology of Calcineurin and Mammalian Target of Rapamycin Inhibitors in Kidney Transplantation

The recent evolution in immunosuppression therapy has led to significant improvement in short-term kidney allograft outcomes; however, this progress did not translate into similar improvement in long-term graft survival. The latter, at least in part, is likely to be attributed to immunosuppressant side effects. In this review, we focus on the histologic manifestations of calcineurin inhibitor and mammalian target of rapamycin inhibitor toxicity. We discuss the pathologic features attributed to such toxicity and allude to the lack of highly specific pathognomonic lesions. Finally, we highlight the importance of clinicopathologic correlation to achieve a meaningful pathologic interpretation.

Comparison of normothermic and hypothermic perfusion in porcine kidneys donated after cardiac death

BACKGROUND

Normothermic machine perfusion (NMP) is an alternative strategy for preserving kidneys donated after cardiac death (DCD). The relative efficacy of prolonged NMP compared to hypothermic machine perfusion (HMP) in DCD kidneys with moderate ischemic injury is undetermined. This study compares NMP and HMP kidney preservation in a porcine DCD model.

METHODS

Ten porcine kidneys underwent NMP or HMP preservation following 45 minutes of warm ischemia and 5 hours of cold ischemia. After 8 hours of machine preservation, hemodynamic stability, renal function, perfusate biomarkers, and histologic integrity were assessed in a simulated reperfusion model.

RESULTS

During simulated reperfusion, no differences were observed in oxygen consumption, urine production, creatinine clearance, fractional excretion of sodium, proteinuria, and perfusate levels of lactate dehydrogenase and aspartate aminotransferase. Resistance was no different after 30 minutes of simulated reperfusion. Histologically, NMP kidneys demonstrated increased vacuolization after preservation and greater loss of tubular integrity after simulated reperfusion. Perfusate levels of alkaline phosphatase (AP) and gamma glutamyltransferase (GGT) were higher in NMP kidneys during preservation, but upon simulated reperfusion, AP and GGT levels were higher in HMP-preserved kidneys. Peak AP and GGT during simulated reperfusion of HMP kidneys were over 14 times higher than peak AP and GGT during preservation of NMP kidneys.

CONCLUSIONS

NMP provided comparable preservation of renal function as HMP and minimized AP and GGT release upon reperfusion.

Sirolimus-induced isometric tubular vacuolization: a new sirolimus histopathologic manifestation

The clinical and pathological experience with sirolimus is limited at this time. In this study, we report severe isometric vacuolization of the proximal tubules after sirolimus therapy in two kidney transplant patients. Patient 1 is a hepatitis C virus-positive, 30-year-old African American man who had end-stage renal disease (ESRD) of unknown etiology. Patient 2 is a 62-year-old white woman with ESRD due to unknown etiology. Both patients were initially placed on tacrolimus, mycophenolic acid, and prednisone immunosuppressive therapy. These patients were switched to sirolimus at 1 and 5 month posttransplant, respectively, due to the development of new-onset hyperglycemia and an elevated serum creatinine. Both patients presented with acute renal failure and high sirolimus levels at 5 years (patient 1) and 10 months posttransplant (patient 2). Biopsies of their kidney transplants showed widespread isometric tubular cytoplasmic vacuolization and severe arterial hyalinosis. Acute renal insufficiency improved after sirolimus dose reduction. In this case report, we introduce a new morphological appearance after sirolimus therapy of isometric cytoplasmic vacuolization of the renal tubules and severe arterial hyalinosis, similar to that seen in calcineurin inhibitor induced tubular toxicity.

Drug-induced Kidney Disease – Pathology and Current Concepts

The kidneys can be damaged by a large number of therapeutic agents. The aim of this article is to discuss the pathological features of drug-induced renal disease as diagnosed by kidney biopsy. The literature is reviewed and cases seen by the authors that have a known drug association are analysed. Mechanisms of injury are varied and all renal structures may be affected. The tubulointerstitial compartment is most frequently involved, but glomerular and vascular lesions are seen in a significant proportion of cases. Key words: Drug, Kidney, Nephrotoxicity, Pathology

High-dosage intravenous immunoglobulin-associated macrovacuoles are associated with chronic tubulointerstitial lesion worsening in renal transplant recipients

BACKGROUND AND OBJECTIVES

Intravenous immunoglobulins (IVIg) may induce acute renal failure associated with tubular vacuolization. Although the use of IVIg is increasing in kidney transplantation, their impact on graft histology and function remains unknown.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Twenty-seven kidney transplant recipients who had high immunologic risk and were treated with four courses of IVIg after transplantation were studied retrospectively at a transplant center, and findings were compared with those of 27 control subjects. Protocol kidney biopsies were performed at time of transplantation and at 3 mo and 1 yr after transplantation.

RESULTS

No episode of IVIg-related acute renal failure occurred. Nevertheless, screening biopsies revealed the presence of "microvacuoles" and "macrovacuoles." Widespread microvacuolizations were often detected (70%) on preimplantation biopsy and not associated with IVIg. Macrovacuoles, which were absent on preimplantation biopsies, were observed exclusively in IVIg-treated patients. Macrovacuoles among IVIg-treated patients were seen in kidneys from older donors and were associated with chronic tubulointerstitial changes at 3 mo, with similar trends at 1 yr. Macrovacuoles were associated with lower creatinine clearance at last follow-up in IVIg-treated patients.

CONCLUSIONS

IVIg frequently induce tubular macrovacuoles in kidney transplant recipients. These are more frequently observed in grafts from older donors, suggesting a higher vulnerability to IVIg. These data suggest a deleterious impact of IVIg-induced macrovacuoles on chronic tubulointerstitial changes and long-term renal function.

Perioperative fluid management in renal transplantation: a narrative review of the literature

Adequate volume maintenance is essential to prevent acute renal failure during major surgery or to ensure graft function after renal transplantation. The various recommendations on the optimum fluid therapy are based, at best, on sparse evidence only from observational studies. This article reviews the literature on perioperative fluid management in renal transplantation. Crystalloid solutions not exerting any specific side-effects are the first choice for volume replacement in kidney transplantation. The use of colloids should be restricted to patients with severe intravascular volume deficits necessitating high volume restoration. The routine application of albumin, dopamine, and high dose diuretics is no longer warranted. Mannitol given immediately before removal of the vessel clamps reduces the requirement of post-transplant dialysis, but has no effects on graft function in the long term. There is insufficient evidence on the best use of dialysis, but it seems peritoneal dialysis pretransplant is associated with less delayed graft function, whereas the preference of dialysis post-transplant is not yet well-founded. This review article should provide better guidance for fluid management in kidney transplantation until best-evidence guidelines can be established based upon more research.

Extending options for highly sensitized patients to receive a suitable kidney graft

Highly sensitized patients (anti-HLA) on the kidney waiting list wait longer for a suitable crossmatch negative organ. At the moment there are two strategies to enhance transplantation of these patients. One approach is the determination of acceptable HLA mismatches and application of this knowledge for the selection of crossmatch negative donors, and the second is the desensitization of patients with intravenous immunoglobulin-based protocols to enable transplantation of an organ from a donor towards which antibodies were originally present. Both approaches have advantages and disadvantages and are only successful in a proportion of the patients. The optimal solution is an integrated strategy whereby desensitization is used for those patients for whom the acceptable mismatch approach is not successful.