D’Costa, Matthew R.

ABSTRACTPurposeThis study aimed to assess whether kidney stone burden and risk factors at the time of kidney donor evaluation were associated with a symptomatic stone event post‐donor evaluation.MethodsWe identified adults evaluated at Mayo Clinic (two sites) (2000–2011) for living kidney donation and had either a personal history or radiological evidence of kidney stone disease. We analyzed demographics, stone risk factors, stone number/size, and the committee's donation decision and reasons. A follow‐up survey (2022–2023) assessed post‐evaluation symptomatic kidney stones and related morbidity.ResultsAmong 412 potential donors with kidney stone disease, 258 donated, 75 did not donate due to kidney stones, and 79 did not donate for other reasons. Multivariable analysis showed that candidates not donating due to stones had higher body mass index (BMI), prior symptomatic kidney stones, multiple stones on imaging, bilateral kidney stones, and diameter of largest stone ≥3 mm. Of 147 who completed the survey, 26 (18%) had a symptomatic kidney stone post‐donor evaluation. Younger age (p = 0.031) and multiple stones on imaging (p = 0.02) were significant predictors of post‐evaluation symptomatic stones regardless of donation status (p = 0.41).ConclusionsStone burden on imaging and prior symptomatic stone events were associated with not donating. Younger age and stone burden on imaging were the primary risk factors for a symptomatic kidney stone event after donor evaluation.

Background The urine metabolites and chemistries that contribute to kidney stone formation are not fully understood. This study examined differences between the urine metabolic and chemistries profiles of first-time stone formers and controls. Methods High-resolution 1 H-nuclear magnetic resonance (NMR) spectroscopy-based metabolomic analysis was performed in 24-hour urine samples from a prospective cohort of 418 first-time symptomatic kidney stone formers and 440 controls. In total, 48 NMR-quantified metabolites in addition to 12 standard urine chemistries were assayed. Analysis of covariance was used to determine the association of stone former status with urine metabolites or chemistries after adjusting for age and sex and correcting for the false discovery rate. Gradient-boosted machine methods with nested cross-validation were applied to predict stone former status. Results Among the standard urine chemistries, stone formers had lower urine oxalate and potassium and higher urine calcium, phosphate, and creatinine. Among NMR urine metabolites, stone formers had lower hippuric acid, trigonelline, 2-furoylglycine, imidazole, and citrate and higher creatine and alanine. A cross-validated model using urine chemistries, age, and sex yielded a mean AUC of 0.76 (95% CI, 0.73 to 0.79). A cross-validated model using urine chemistries, NMR-quantified metabolites, age, and sex did not meaningfully improve the discrimination (mean AUC, 0.78; 95% CI, 0.75 to 0.81). In this combined model, among the top ten discriminating features, four were urine chemistries and six NMR-quantified metabolites. Conclusions Although NMR-quantified metabolites did not improve discrimination, several urine metabolic profiles were identified that may improve understanding of kidney stone pathogenesis.

Background. Nephrolithiasis in living kidney donors is concerning due to the potential impact on long-term postdonation kidney function. Methods. We performed a cohort study of living kidney donors from 2 centers with a baseline computed tomography scan and implantation renal biopsy. Donors (>5 y since donation) completed a follow-up survey or underwent chart review to assess eGFR and incident hypertension. Stone formers were classified as symptomatic if they had a past symptomatic episode or asymptomatic if only incidental radiographic kidney stones were identified during donor evaluation. We compared baseline clinical, imaging, and biopsy characteristics by stone former status including review of metabolic evaluations in stone formers. Long-term risks of renal complications (low eGFR and hypertension) by stone former status were evaluated. Results. There were 12 symptomatic and 76 asymptomatic stone formers among 866 donors. Overall, baseline clinical characteristics and implantation biopsy findings were similar between stone formers and non-stone formers. After a median follow-up of 10 y, stone former status was not associated with eGFR <60 mL/min/1.73 m2, eGFR <45 mL/min/1.73 m2, or hypertension. Conclusions. Both asymptomatic and symptomatic SF have favorable histology findings at baseline. Long-term kidney outcomes were favorable in select stone formers with no evident increased long-term risk for decreased kidney function or hypertension after donation.

Background. Improving both patient and graft survival after kidney transplantation are major unmet needs. The goal of this study was to assess risk factors for specific causes of graft loss to determine to what extent patients who develop either death with a functioning graft (DWFG) or graft failure (GF) have similar baseline risk factors for graft loss. Methods. We retrospectively studied all solitary renal transplants performed between January 1, 2006, and December 31, 2018, at 3 centers and determined the specific causes of DWFG and GF. We examined outcomes in different subgroups using competing risk estimates and cause-specific Cox models. Results. Of the 5752 kidney transplants, graft loss occurred in 21.6% (1244) patients, including 12.0% (691) DWFG and 9.6% (553) GF. DWFG was most commonly due to malignancy (20.0%), infection (19.7%), cardiac disease (12.6%) with risk factors of older age and pretransplant dialysis, and diabetes as the cause of renal failure. For GF, alloimmunity (38.7%), glomerular diseases (18.6%), and tubular injury (13.9%) were the major causes. Competing risk incidence models identified diabetes and older recipients with higher rates of both DWFG and nonalloimmune GF. Conclusions. These data suggest that at baseline, 2 distinct populations can be identified who are at high risk for renal allograft loss: a younger, nondiabetic patient group who develops GF due to alloimmunity and an older, more commonly diabetic population who develops DWFG and GF due to a mixture of causes—many nonalloimmune. Individualized management is needed to improve long-term renal allograft survival in the latter group.

AbstractBackgroundThe medium‐ to long‐term outcomes of living kidney donors with hypertension compared to normotensive donors are not well understood, especially with the recent changes in hypertension guidelines.MethodsWe studied a cohort of 950 living kidney donors using different definitions of hypertension based on either ≥140/90 or ≥130/80 mmHg thresholds and based on either office or ambulatory blood pressure readings. Microstructural features on kidney biopsy at the time of donation were compared using different definitions of hypertension.ResultsAfter adjusting for years of follow‐up, age, sex, and baseline eGFR, hypertension (by any definition) did not significantly predict an eGFR < 45 ml/min/1.73 m2 at a median follow‐up of 10 years postdonation, though there was a borderline association with ambulatory blood pressure ≥ 130/80 mmHg predicting a 40% decline in eGFR (OR = 1.53, 1.00–2.36; p = .051). Proteinuria was predicted by office blood pressure ≥ 140/90 mmHg and by nondipper profile on nocturnal ambulatory blood pressure measurements. At the time of donation, larger glomeruli and arterial hyalinosis on biopsy were associated with hypertension defined by either ≥140/90 or ≥130/80 mmHg (by office or ambulatory measurements). Nocturnal nondipper status was associated with larger glomeruli size but not arteriolar hyalinosis when compared to dippers.ConclusionsIn programs that accept donors with controlled hypertension, various definitions of hypertension are associated with histological findings in the donated kidney, but none predict a clinically significant decline in kidney function 10 years after donation. These data support allowing healthy individuals with controlled hypertension to donate a kidney. However, donors with office hypertension (≥140/90 mmHg) and nondippers (regardless of hypertension status) are at greater long‐term risk for proteinuria, and particularly for these donors, longer follow‐up is warranted.

Background. At 5 and 10 y after kidney transplantation, chronic histologic changes such as arteriolar hyalinosis and mesangial expansion are common; however, determining cause is difficult. We compared surveillance biopsies in living donor kidney transplants (LDKTx) from HLA-matched siblings (termed HLA-identical [HLA-ID]) with HLA non-ID to investigate which histologic changes were likely due to alloimmune injury and which were due to nonalloimmune injury. Methods. We performed a retrospective, cohort study comparing HLA-ID sibling LDKTx (n = 175) with HLA non-ID LDKTx (n = 175; matched for age, sex, and year of transplant ±2 y) performed at a single institution from March 1999 to November 2018. Results. Baseline characteristics and maintenance immunosuppression were similar. Mortality rates were similar, but in the HLA-ID group, 10-y death-censored graft survival was higher (93.8% versus 80.9% HLA non-ID LDKTx; P < 0.001), rejection rates were lower (after 1 y 9.6% versus 27.1%; P < 0.001), and Banff inflammation scores including glomerulitis and peritubular capillaritis were lower on surveillance biopsies at 1, 5, and 10 y. In contrast, chronic Banff scores (interstitial fibrosis, arteriolar hyalinosis, mesangial expansion, etc) were similar in prevalence and severity on surveillance biopsies at 1, 5, and 10 y. Conclusions. HLA-ID LDKTx have less inflammation and less transplant glomerulopathy, but most chronic histologic changes were similar to less well-matched LDKTx. We conclude that these types of chronic changes are not associated with HLA mismatches and may be due to nonimmunologic causes (hypertension, obesity, etc), suggesting that new management approaches to prevent these lesions may be needed.

AbstractDeath with a functioning graft and death‐censored renal allograft failure remain major problems for which effective preventative protocols are lacking. The retrospective cohort study aimed to determine whether histologic changes on a 5‐year surveillance kidney biopsy predict adverse outcomes after transplantation in recipients who had: both Type 2 diabetes (T2DM) and obesity (BMI ≥ 30 kg/m2) at the time of transplantation (T2DM/Obesity, n = 75); neither (No T2DM/No obesity, n = 78); No T2DM/Obesity (n = 41), and T2DM/No obesity (n = 47). On 5‐year biopsies, moderate‐to‐severe mesangial expansion was more common in the T2DM/Obesity group (Banff mm score ≥2 = 49.3%; Tervaert classification MS ≥ 2b = 26.7%) compared to the other groups (p < .001 for both scores). Risk factors included older age, higher BMI, HbA1C, and triglycerides at 1‐year post‐transplant. Moderate‐to‐severe mesangial expansion correlated with death with function (HR 1.74 (1.01, 2.98), p = .045 Banff and 1.89 (1.01, 3.51) p = .045 Tervaert) and with death‐censored graft loss (HR 3.2 (1.2, 8.8), p = .02 Banff and HR 3.8 (1.3, 11.5), p = .01 Tervaert) over a mean of 11.6 years of recipient follow‐up post‐transplant. These data suggest that mesangial expansion in recipients with T2DM and obesity may reflect systemic vascular injury and might be a novel biomarker to predict adverse outcomes post renal transplant.