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Two metrics, a rise in serum creatinine concentration and a decrease in urine output, are considered tantamount to the injury of the kidney tubule and the epithelial cells thereof (AKI). Yet neither criterion emphasizes the etiology or the pathogenetic heterogeneity of acute decreases in kidney excretory function. In fact, whether decreased excretory function due to contraction of the extracellular fluid volume (vAKI) or due to intrinsic kidney injury (iAKI) actually share pathogenesis and should be aggregated in the same diagnostic group remains an open question. To examine this possibility, we created mouse models of iAKI and vAKI that induced a similar increase in serum creatinine concentration. Using laser microdissection to isolate specific domains of the kidney, followed by RNA sequencing, we found that thousands of genes responded specifically to iAKI or to vAKI, but very few responded to both stimuli. In fact, the activated gene sets comprised different, functionally unrelated signal transduction pathways and were expressed in different regions of the kidney. Moreover, we identified distinctive gene expression patterns in human urine as potential biomarkers of either iAKI or vAKI, but not both. Hence, iAKI and vAKI are biologically unrelated, suggesting that molecular analysis should clarify our current definitions of acute changes in kidney excretory function.

Biopsy findings at the time of procurement of deceased donor kidneys remain the most common reason cited for kidney discard. To determine the value of renal allograft histology in predicting outcomes, we evaluated the significance of histologic findings, read by experienced renal pathologists, in 975 postreperfusion biopsy specimens collected from 2005 to 2009 after living donor (=427) or deceased donor (=548) renal transplant. We evaluated specimens for the degree of glomerulosclerosis, interstitial fibrosis and tubular atrophy, and vascular disease; specimens with a score of 0 or 1 (scale, 0-3) for each parameter were considered optimal. Overall, 66.3% of living donor kidneys and 50.7% of deceased donor kidneys received an optimal histology score (<0.001). Irrespective of donor status, suboptimal kidneys came from older donors with a higher incidence of diabetes mellitus, hypertension, and obesity and a higher mean kidney donor risk index (all <0.001). Death-censored outcomes after transplant differed significantly between optimal and suboptimal kidneys only in the deceased donor transplants (=0.02). Regardless of histologic classification, outcomes with deceased donor kidneys were inferior to outcomes with living donor kidneys. However, 73.2% of deceased donor kidneys with suboptimal histology remained functional at 5 years. Our findings suggest that histologic findings on postreperfusion biopsy associate with outcomes after deceased donor but not living donor renal transplants, thus donor death and organ preservation-related factors may be of greater prognostic importance. Discarding donated kidneys on the basis of histologic factors may be inappropriate and merits further study.

Background: Most studies that have assessed the predictors of recurrent IgA nephropathy (IgAN) in the renal allograft have focused on post-transplant features. Identifying high-risk pre-transplant features of IgAN is useful for counseling patients and may help in tailoring post-transplant immunosuppression. Methods: We investigated the pre-transplant clinical and biopsy features of 62 patients with IgAN who received transplants at Columbia University Medical Center from 2001 to 2012 and compared the characteristics and outcomes of patients with IgAN recurrence to those without recurrence. The primary outcome was time to recurrent IgAN. Secondary outcomes were a composite of doubling of creatinine or allograft failure, and recurrent IgAN as a cause of allograft dysfunction. Results: Of the 62 patients, 14 had recurrent IgAN in the allograft. Mean time to recurrence was 2.75 years. Those with recurrent disease were younger at the time of native kidney biopsy (29 vs. 41 years, p < 0.0009). Black race and Hispanic ethnicity composed a higher proportion of the recurrent disease group. On multivariable analysis, significant predictors of recurrent IgAN included age at diagnosis (hazards ratio (HR) 0.911, 95% CI 0.85-0.98), burden of crescents on native biopsy (HR 1.21 per 10% increase in crescents, 95% CI 1.00-1.47) and allograft rejection (HR 3.59, 95% CI 1.10-11.7). Conclusions: Features of native IgAN can help predict the risk of recurrent disease in the renal allograft. In particular, immunologically active disease represented by earlier age of onset and greater burden of crescents on native biopsy is more likely to recur after transplant.

HIV-associated nephropathy (HIVAN) is a unique form of collapsing focal segmental glomerulosclerosis that typically occurs in patients with advanced HIV disease. The pathogenesis of HIVAN involves direct HIV infection and gene expression in tubular and glomerular epithelial cells; in effect, HIVAN can be considered a natural illustration of gene delivery to the kidney. HIV infection or expression of HIV genes results in dysregulation of tubular and glomerular epithelial cells and induction of local inflammatory cascades. Specific HIV genes, in particular Nef and Vpr, play prominent and synergistic roles in the pathogenesis of HIVAN, while other viral genes are not required for the development of HIVAN. The disproportionate burden of HIVAN and HIV-related end-stage renal disease in blacks suggests that host genetic factors are also important in the pathogenesis of HIVAN. Preliminary genetic studies in the mouse model have identified a potential genetic susceptibility locus, and a number of host genes are differentially expressed in the setting of HIVAN or HIV infection. The current management of HIVAN couples antiretroviral therapy with adjunctive agents that target downstream effects of HIV gene expression in the kidney. Future therapies could also target different steps in the pathogenesis of HIVAN, including viral replication, epithelial cell entry and viral gene expression, and downstream cellular pathways.

A 44-year-old woman with no medical history presented with edema and dyspnea of 4-week duration. Imaging revealed bilateral pleural effusions and mild anasarca. Serum creatinine was 1.57 mg/dl, and urine protein was 1.336 g/24 h. The patient was anemic (Hgb 8.2), thrombocytopenic (plt 29), and hypertensive (BP 184/109). A kidney biopsy showed a glomerular thrombotic microangiopathy (TMA)-like pattern without true fibrin thrombi and no fibrosis (Figure 1, A and B). A bone marrow biopsy showed reactive megakaryocyte hyperplasia. Serologic testing also revealed

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