Comparison of kidney transplant outcomes in HLA compatible and incompatible transplantation: a national cohort study

BACKGROUND

Reports of HLA incompatible (HLAi) kidney transplant outcomes are inconclusive, especially in the context of lower level Donor Specific Antibodies (DSA).

METHODS

Multi-centre national cohort study of HLAi kidney transplant recipients matched in 1:2 ratio with HLA compatible (HLAc) kidney transplant recipients. HLAi defined as DSA identified by Luminex. Antibody mediated rejection (AMR) and transplant-survival were analysed using Kaplan-Meier plots. Propensity score (PS) matching was used to compare recipient and transplant survival between groups.

RESULTS

We included 61 HLAi and 122 HLAc recipients; mean age 46 years; 60% female. MFI_T0 : 3327 (IQR 1352 - 6458), 23 (38%) were Flow cytometry crossmatch positive (FC-XM_POS) . DSA_POS /FC-XM_POS transplantation carried an increased risk of AMR at 1 year (52%) compared to DSA_POS /FC-XM_NEG (27%) and HLAc (0%). Unadjusted death censored graft loss at 3 years was 13% (HLAi) and 8% (HLAc). Three-year patient survival was 95% in HLAc, 84% in DSA_POS /FC-XM_NEG and 69% in DSA_POS /FC-XM_POS recipients; 58% of HLAi deaths were infection-related. HLA incompatibility was associated with a decreased 3-year survival in our PS-matched cohort.

CONCLUSION

In kidney transplantation, DSA and positive FC-XM carries an increased risk of AMR. Despite inferior transplant and survival outcomes compared to HLAc transplantation, it remains a realistic option for highly sensitised patients facing prolonged waiting times and reduced survival on dialysis.

Perfusate Composition and Duration of Ex-Vivo Normothermic Perfusion in Kidney Transplantation: A Systematic Review

Ex-vivo normothermic perfusion (EVNP) is an emerging strategy in kidney preservation that enables resuscitation and viability assessment under pseudo-physiological conditions prior to transplantation. The optimal perfusate composition and duration, however, remain undefined. A systematic literature search (Embase; Medline; Scopus; and BIOSIS Previews) was conducted. We identified 1,811 unique articles dating from January 1956 to July 2021, from which 24 studies were deemed eligible for qualitative analysis. The perfusate commonly used in clinical practice consisted of leukocyte-depleted, packed red blood cells suspended in Ringer’s lactate solution with Mannitol, dexamethasone, heparin, sodium bicarbonate and a specific nutrient solution supplemented with insulin, glucose, multivitamins and vasodilators. There is increasing support in preclinical studies for non-blood cell-based perfusates, including Steen solution, synthetic haem-based oxygen carriers and acellular perfusates with supraphysiological carbogen mixtures that support adequate oxygenation whilst also enabling gradual rewarming. Extended durations of perfusion (up to 24 h) were also feasible in animal models. Direct comparison between studies was not possible due to study heterogeneity. Current evidence demonstrates safety with the aforementioned widely used protocol, however, extracellular base solutions with adequate oxygenation, supplemented with nutrient and metabolic substrates, show promise by providing a suitable environment for prolonged preservation and resuscitation.

Systematic Review Registration:https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42021231381, identifier PROSPERO 2021 CRD42021231381

The New UK National Kidney Allocation Scheme With Maximized "R4-D4" Kidney Transplants: Better Patient-to-Graft Longevity Matching May Be at the Cost of More Resources

OBJECTIVES

A new kidney matching scheme for allocation of deceased donor kidneys for transplantation was introduced in the United Kingdom in September 2019. Donors and recipients are stratified into quartiles derived from demographic and retrieval indices associated with risk of adverse outcome. We present data on 2 years of transplants, with the aim of understanding the potential impacts ofthe scheme on patient/transplant outcomes, hospitalization, and resource utilization.

MATERIALS AND METHODS

All deceased donortransplants from 2015 and 2016 were reclassified using the risk quartiles (D1-D4 for donor and R1-R4 for recipient, where 4 is highestrisk). Inpatientlength of stay, kidney function defined by estimated glomerular rate at 1 year, and patient survival data were collected.

RESULTS

Of the 195 deceased donor transplants analyzed, 144 recipients (73.4%) were in the highest risk R4 category, including 55 with R4-D4 combination (28.1%). Recipients in the R4 category had longer index admissions (mean of 12.4 vs 8.1 days for R1-R3; P = .002) and higher subsequent admission rates 90 days posttransplant(185.7 vs 122.7/1000 patient days for R1-R3; P < .001). Kidney transplant function at 1 year was lower for grafts categorized as D4 (mean estimated glomerular filtration rate of 35.7 vs 54.8 mL/min/1.73 m2 for D1-D3; P < .001). However, survival for R4 recipients with D4 kidneys was not significantly differentfrom R4 recipients with D1 to D3 kidneys (4-year patient survival rate with R4-D4 combination was 90.9%).

CONCLUSIONS

The principles ofthe allocation scheme in matching graft and patient survival were already largely being observed (matching higher risk deceased donor kidneys to higher risk recipients). However, an increase in D4 proportions in the R4 group may be associated with longer hospitalization posttransplant. Consideration should be given to mitigation strategies to address this. Despite poorer graft function, patient survival appears satisfactory.

Viability assessment and utilization of declined donor kidneys with rhabdomyolysis using ex vivo normothermic perfusion without preimplantation biopsy

The role of ex vivo normothermic perfusion (EVNP) in both organ viability assessment and reconditioning is increasingly being demonstrated. We report the use of this emerging technology to facilitate the transplantation of a pair of donor kidneys with severe acute kidney injury (AKI) secondary to rhabdomyolysis. Donor creatinine was 10.18 mg/dl with protein (30 mg/dl) present in urinalysis. Both kidneys were declined by all other transplantation units and subsequently accepted by our unit. The first kidney was perfused with red cell-based perfusate at 37°C for 75 min, mean renal blood flow was 110 ml/min/100 g and produced 85 ml of urine. Having demonstrated favorable macroscopic appearance and urine output, the kidney was transplanted into a 61-year-old peritoneal dialysis dependent without complication. Given the reassuring information from the first kidney provided by EVNP, the second kidney was not perfused with EVNP and was directly implanted to a 64-year-old patient. The first kidney achieved primary function and the second functioned well after delayed graft function. Recipient eGFR have stabilized at 88.5 and 55.3, respectively (ml/min/1.73 m² ), at 2 months posttransplant.

The impact of age on patient tolerance of mycophenolate following kidney transplantation

BACKGROUND

In Scotland, standard maintenance immunosuppression following kidney transplantation consists of mycophenolate (MPA), tacrolimus and prednisolone irrespective of recipient age. We analyzed the tolerability of this immunosuppression regimen and the association with transplant outcomes.

METHODS

A national, multicentre retrospective analysis of patients transplanted in 2015 and 2016, comparing graft function, acute rejection, significant infection rates and immunosuppression dosing between patients aged 18 and 59 years (Group 1) and ≥60 years (Group 2).

RESULTS

Of the 490 patients, 26% were aged ≥60 years. Acute rejection (AR) rates at 1 year were 15% and 11% in Groups 1 and 2, respectively. Full-dose MPA was poorly tolerated with 53% in Group 1 and 77% in Group 2 requiring dose reduction or cessation. Female gender and age ≥60 years were independent predictors for MPA dose changes. One year following MPA dose reduction, AR risk was low (5%) in Group 2, however, those remaining on full dose MPA had a 79% increased rate of serious infections.

CONCLUSION

The majority of renal transplant recipients aged ≥60 fail to tolerate full-dose MPA. In this group, MPA dose reduction is associated with low rejection rates, but full-dose MPA is associated with high infection rates. We suggest that a tailored approach to immunosuppression in elderly recipients incorporating lower doses of MPA may be appropriate.

Characterizing the early inflammatory contribution of the donor kidney following reperfusion

Background

Donor kidneys contain a large reservoir of passenger leucocytes that contribute to acute rejection via direct alloantigen presentation and pro-inflammatory cytokine secretion. However, the early contribution of these cells following revascularization has not previously been described. We performed a secondary, high-volume preservation flush following cold storage to characterize the inflammatory contribution of the donor kidney upon reperfusion.

Methods

Porcine kidneys were retrieved using a protocol analogous to current UK clinical practice. Following 2 h of cold static preservation, kidneys underwent a secondary flush with Ringer's solution. The venous effluent was collected and leucocytes phenotyped via flow cytometry. Inflammatory mediators, including cytokines and cell-free DNA, were then assessed to determine the inflammatory contribution of the donor kidney.

Results

Upon reperfusion, a significant population of donor-derived CD45 +  leucocytes mobilized from the renal vasculature via the renal vein [mean 4.738 × 10 8  (SD 1.348 × 10 8 )]. Within this population, T cells were dominant, representing >60% of the leucocyte repertoire. Granulocytes, monocytes and natural killer cells were also identified, but in comparatively lower numbers. Significant concentrations of cytokines and cell-free DNA were also eluted upon reperfusion.

Conclusions

The donor kidney contains a significant immune load that rapidly mobilizes following reperfusion. Performing a secondary preservation flush prior to implantation may reduce this inflammatory burden via diversion of donor leucocytes and inflammatory mediators from entry into the recipient circulation. This may modulate direct presentation and reduce the inflammatory contribution of the donor kidney following transplantation.

Deleterious effects of phosphate on vascular and endothelial function via disruption to the nitric oxide pathway

Background

Hyperphosphataemia is an independent risk factor for accelerated cardiovascular disease in chronic kidney disease (CKD), although the mechanism for this is poorly understood. We investigated the effects of sustained exposure to a high-phosphate environment on endothelial function in cellular and preclinical models, as well as in human subjects.

Methods

Resistance vessels from rats and humans (± CKD) were incubated in a normal (1.18 mM) or high (2.5 mM) phosphate concentration solution and cells were cultured in normal- (0.5 mM) or high-phosphate (3 mM) concentration media. A single-blind crossover study was performed in healthy volunteers, receiving phosphate supplements or a phosphate binder (lanthanum), and endothelial function measured was by flow-mediated dilatation.

Results

Endothelium-dependent vasodilatation was impaired when resistance vessels were exposed to high phosphate; this could be reversed in the presence of a phosphodiesterase-5-inhibitor. Vessels from patients with CKD relaxed normally when incubated in normal-phosphate conditions, suggesting that the detrimental effects of phosphate may be reversible. Exposure to high-phosphate disrupted the whole nitric oxide pathway with reduced nitric oxide and cyclic guanosine monophosphate production and total and phospho endothelial nitric oxide synthase expression. In humans, endothelial function was reduced by chronic phosphate loading independent of serum phosphate, but was associated with higher urinary phosphate excretion and serum fibroblast growth factor 23.

Conclusions

These directly detrimental effects of phosphate, independent of other factors in the uraemic environment, may explain the increased cardiovascular risk associated with phosphate in CKD.

Ex Vivo Normothermic Perfusion Induces Donor-Derived Leukocyte Mobilization and Removal Prior to Renal Transplantation

Introduction

Ex vivo normothermic perfusion offers an alternative method of organ preservation, allowing donor kidneys to be reanimated and evaluated prior to transplantation. Beyond preservation, it can be used to characterize the immunological contribution of the donor kidney in isolation. Furthermore, it has the potential to be used as an immunomodulatory strategy to manipulate donor kidneys prior to transplantation.

Methods

Explanted porcine kidneys underwent 6 hours of perfusion. Sequential perfusate samples were collected and leukocytes characterized via flow cytometry. An inflammatory profile was generated via cytokine quantification. Cell-free DNA was also determined as markers of cell death.

Results

All kidneys functioned within normal parameters and met the criteria for transplantation at the end of perfusion. Throughout perfusion there were continuous increases in pro-inflammatory cytokines, including large concentrations of interferon-γ, suggesting that perfusion drives a significant inflammatory response. Increasing concentrations in cell-free DNA were also observed, suggesting cell death. During perfusion there was a marked cellular diapedesis of T cells, B cells, natural killer (NK) cells, and monocytes from the kidney into the circuit. Minor populations of granulocytes and macrophages were also detected.

Discussion

We demonstrate that ex vivo normothermic perfusion initiates an inflammatory cytokine storm and release of mitochondrial and genomic DNA. This is likely to be responsible for immune cell activation and mobilization into the circuit prior to transplantation. Interestingly this did not have an impact on renal function. These data therefore suggest that normothermic perfusion can be used to immunodeplete and to saturate the pro-inflammatory capacity of donor kidneys prior to transplantation.

Predictors of sustained arteriovenous access use for haemodialysis

BACKGROUND

Guidelines encourage early arteriovenous (AV) fistula (AVF) planning for haemodialysis (HD). The aim of this study was to estimate the likelihood of sustained AV access use taking into account age, sex, comorbidity, anatomical site of first AVF and, for pre-dialysis patients, eGFR and proteinuria.

METHODS

1,092 patients attending our centre who had AVF as their first AV access procedure between January 1, 2000 and August 23, 2012 were identified from the electronic patient record. The primary end-point was time to first sustained AV access use, defined as use of any AV access for a minimum of 30 consecutive HD sessions.

RESULTS

52.9% (n = 578) of the patients ultimately achieved sustained AV access use. The main reasons for AV access non-use were AVF failure to mature and death. The 3-year Kaplan-Meier probability of sustained AV access use was 68.8% for those not on renal replacement therapy (RRT) (n = 688) and 74.2% for those already on RRT (n = 404) at the time of first AVF. By multivariate analysis in patients not on RRT, male sex (HR 2.22; p < 0.001), uPCR (HR 1.03; p = 0.03) and eGFR (hazard ratio, HR 0.85; p < 0.001) were independent predictors of AV access use. In patients already on RRT, age (HR 0.98; p < 0.001) and peripheral vascular disease (HR 0.48; p = 0.02) were independent predictors of AV access use.

CONCLUSION

Our data suggest that refinement of the current guideline for timing of AV access creation in planning RRT is justified to take into account individual factors that contribute to the likelihood of technical success and clinical need.

Hand-assisted laparoscopic living donor nephrectomy: initial Glasgow experience

AIMS

The study presents the early results of hand-assisted laparoscopic living donor nephrectomy (HALDN) carried out in West of Scotland from June 2009 to October 2010.

METHODS

The first 20 HALDN procedures carried out in our unit are presented. The outcomes reported are warm ischaemia time, operative time, delayed graft function, recipient renal function and one-month morbidity and mortality of donor and recipient. SPSS 15.0 was used for statistical analysis.

RESULTS

The mean age of the donors was 44 ± 10 years, predominantly females (n = 13), median operative time 135 ± 33 min and warm ischaemia time 41 ± 16 s. The length of the incision used was 65 mm in all cases. Duration of hospital stay was 5 ± 1 days. Patient mortality was 0 and morbidity minimal with two donors developing minor wound infection and no other clinically significant postoperative morbidity. Among the recipients, 18/20 (90%) transplants worked primarily with two delayed graft functions, one due to early surgical complications in a small paediatric recipient and one due to recipient renal artery thrombosis.

CONCLUSION

HALDN is safe and associated with minimal morbidity; further analysis aims to confirm excellent cosmetic results and quick return to activity compared with the standard open nephrectomy technique.

Pyogenic ventriculitis following enteral bacterial translocation in a patient with small bowel obstruction

The authors present a rare case of ventriculitis secondary to cerebro spinal fluid (CSF) colonization with Escherichia coli species in a 65-year-old woman. Passage of bacterial organisms from the lumen of the gastrointestinal tract to the bloodstream or lymphatic tissue is known as translocation. Once in the bloodstream, particular bacteria are able to cross the blood-brain barrier and migrate to CSF. Elective abdominal surgery, intestinal obstruction, colorectal cancer, ischaemic reperfusion injury and pancreatitis have all increased the risk of this phenomenon. This account highlights particular events in presentation and management of such a case, followed by a brief literature review.

Single-center experience of encapsulating peritoneal sclerosis in patients on peritoneal dialysis for end-stage renal failure

BACKGROUND

Encapsulating peritoneal sclerosis (EPS) is a rare but serious complication in patients undergoing continuous ambulatory peritoneal dialysis (CAPD) or automated peritoneal dialysis (APD). It is characterized by a progressive, intra-abdominal, inflammatory process resulting in sheets of fibrous tissue that cover, bind, and constrict the viscera, thereby compromising the motility and function of the bowel. Although recent therapeutic approaches have been reported with variable success, the ability to detect reliably at an early stage patients at risk for EPS would be beneficial and allow treatment standardization. The aim of this study was to evaluate the clinical features of EPS and identify possible risk factors for its development in CAPD and APD patients.

METHODS

This was a review of all cases of EPS in a single center over the last 5 years.

RESULTS

There were 810 CAPD and APD patients, managed in our program over this period. We identified 27 cases of EPS, giving an overall of 3.3% in this population. The mean duration of CAPD before diagnosis of EPS was 72.6 +/- 39.7 months (range 16-172). Sixteen cases required surgical treatment and were classified as severe; others were treated conservatively (mild to moderate group). Ten patients received tamoxifen treatment with apparent benefit. The overall mortality rate was 29.6%. Eight patients from the severe group and the entire moderate group survived on hemodialysis or transplantation at 48.71 and 27.63 months follow-up, respectively. Peritonitis rates were not different between the 2 groups and peritoneal history was unremarkable compared to overall peritonitis rates in the unit. Data on small solute transport were not available in all patients in this retrospective analysis.

CONCLUSION

EPS is a serious, life-threatening complication of CAPD. Most cases had PD duration of more than 4 years. Careful monitoring by CT scans of the peritoneal membrane in patients beyond 5 years, and early catheter removal in patients with peritoneal thickening should be considered for long-term CAPD patients. Treatment with tamoxifen may be of benefit in these patients.

Laryngopharyngeal pH measurement

OBJECTIVES

Most emergency department (ED) intubations are to prevent gastric contents aspiration. The incidence of aspiration is unknown and intubation has complications. Balancing these risks requires an idea of the incidence of aspiration. This study assessed one technique for investigating the aspiration risk in ED patients. Cricoid pressure is used to reduce this risk and the technique may also examine this manoeuvre.

METHODS

Cohorts of unconscious adult ED and elective surgical patients were recruited. The posterior pharyngeal wall pH was measured immediately before and after intubation. Pharyngeal pH was used to indicate risk of aspiration, and pH change to assess the efficacy of cricoid pressure.

RESULTS

Eight ED and 48 control patients were recruited. In the ED cohort, pH ranged from 6.0 to 8.0 before intubation and 4.7 to 8.0 after intubation: a mean decrease of 0.3 (95% CI 1.5 decrease to 0.9 increase). In the control cohort pH ranged from 5.8 to 8.0 before intubation and 6.0 to 8.0 after intubation: a mean increase of 0.4 (95% CI 0.1 to 0.6 increase).

CONCLUSIONS

This is a simple, cheap, and repeatable technique for assessing aspiration risk in emergency intubations. A larger study is required to assess the efficacy of cricoid pressure.

Bronchoscopic removal of an inhaled, sharp, foreign body: an unusual complication

A case is reported in which an inhaled sewing needle, stuck fast in the trachea, became displaced through the tracheal wall during attempted removal via flexible bronchoscopy. The inherent risks and pitfalls of this procedure are highlighted.