Human Leukocyte Antigen Homozygosity Contributes to Sensitization in Kidney Transplant Candidates

Background: Homozygosity for human leukocyte antigens (HLA) has been associated with adverse outcomes after viral infection as well as pregnancy-induced HLA sensitization. We sought to assess the relationship between HLA locus homozygosity and the level of HLA antibody sensitization. Methods: We measured sensitization using the calculated panel reactive antibody (CPRA) value for a large cohort of 147,461 patients added to the US OPTN/UNOS kidney transplant waitlist between December 2014 and December 2019. We used multinomial logistic modeling to compare 62,510 sensitized patients to 84,955 unsensitized controls. Results: We found that the number of homozygous HLA loci was strongly associated with the level of sensitization. Within highly- or extremely-sensitized candidates, women displayed a higher relative abundance of HLA homozygosity at multiple HLA loci as compared to men, with attenuation of this effect in Black candidates. In multinomial logistic modeling, the number of homozygous HLA loci was an independent predictor of sensitization and interacted with female sex but not with other factors associated with sensitization. Conclusions: This study shows that HLA homozygosity is an innate genetic factor that contributes to HLA sensitization, and enhances the effect of pregnancy-related sensitization.

The Tangential Extraperitoneal Retrorenal Approach in Kidney Transplant Biopsy: An Observational Study to Assess Complication and Adequacy Rates

Introduction: Ultrasound-guided percutaneous kidney allograft biopsy is the gold-standard for pathology work-up. Recent studies postulate better safety and efficacy for tangential approaches, however, there is no recommendation regarding biopsy needle path. In this context, we previously described the unified tangential extraperitoneal retrorenal (TER) approach for standard allograft biopsy.Methods: A single-center retrospective observational study evaluated safety and efficacy of the TER biopsy approach among 250 patients that underwent 330 ultrasound-guided kidney transplant biopsies between January 2011 and May 2020.Results: The overall major complication rate was 0.56% per biopsy attempt (1.21% per biopsy) including blood transfusion, arterial embolization and bladder catheterization for gross hematuria in 0.28, 0.14 and 0.14% of biopsy attempts, respectively (0.61, 0.30 and 0.30% of biopsies, respectively). Minor complications included subcapsular and/or perinephric hematoma, superficial bleeding, arteriovenous fistula and gross hematuria in 12.6, 3.0, 2.5 and 1.4% of biopsy attempts, respectively (27.0, 6.4, 5.5 and 3.0% of biopsies, respectively). Sample adequacy rate was 86.7%, ranging from 82.2 to 94.1% if one or ≥two cores were analyzed, respectively. Residents and consultants yielded similar complication and adequacy rates.Conclusion: According to current literature, ultrasound-guided TER kidney transplant biopsy is a safe and efficient approach eligible for nephrology training.

Arterial Embolization of Polycystic Kidneys for Heterotopic Transplantation

Introduction: The purpose of this study was to evaluate the efficacy of polycystic kidney embolization, performed to reduce kidney volume before heterotopic kidney transplantation, as this technique could be an alternative to pretransplant nephrectomy. Materials and Methods: All patients who underwent pretransplant embolization of polycystic kidneys were included in a prospective register from June 2014 to February 2020. All patients underwent computed tomography (CT) scan with volumetric reconstruction (OsiriX, Bernex, Switzerland) before embolization and were then followed up at 3 and 6 months after embolization. Primary outcome was percentage of kidney volume reduction. Secondary outcomes were 30 day mortality and morbidity. Results: Thirty-one embolizations performed on 29 patients (medium age = 55.6; 62.1% male) were included between June 2014 and February 2020. All patients were under dialysis before embolization (9 peritoneal dialysis and 20 hemodialysis). Technical success was observed in 96.8% of cases. Mean procedural time was 65 minutes (range = 35–106 minutes) and mean length of in-hospital stay was 3.8 days (range = 3–6 days). A volume reduction allowing a kidney transplant was obtained for 28 patients (96.5%). The mean volume reduction was 39.9% (range = 6.01–68.2). The main observed complication was postembolization pain in 10 cases (32.2%). One patient needed complementary nephrectomy due to insufficient volume reduction. Twenty-three patients (79.3%) received renal transplant during follow-up with a mean delay of 19.5 month (range = 4–54). Conclusion: Polycystic kidney embolization is an effective and safe minimally invasive technique. It can be proposed as the first-choice technique for kidney transplant recipients as an alternative to pretransplantation nephrectomy.