Kidney Biopsy Findings Among Allogenic Hematopoietic Stem Cell Transplant Recipients With Kidney Injury: A Case Series.

Rationale and Objective: The incidence of kidney disease is high in patients after allogeneic hematopoietic cell transplantation (aHCT). Although rarely performed, kidney biopsy may be useful to make a precise diagnosis because several mechanisms and risk factors can be involved, and to adjust the treatment accordingly. This case series aimed to report the spectrum of biopsy findings from patients with kidney injury after aHCT. Study Design: Single-center retrospective case series. Setting and Participants: All individuals who underwent a native kidney biopsy, among all adult patients who received aHCT in a tertiary hospital in Montreal (Canada) from January 1, 2010, to December 31, 2020, were identified, and the clinical data were extracted from their medical records. Results: A total of 17 patients were included. Indications for biopsy included acute kidney injury (n=6), chronic kidney disease (n=5), nephrotic syndrome (n=4), and subnephrotic proteinuria (n=2). Pathologic findings from the kidney biopsy were heterogenous: 10 patients showed evidence of thrombotic microangiopathy (TMA), 5 of acute tubular injury, and 4 of membranous nephropathy. Cases of acute interstitial nephritis, BK virus nephropathy, immune complex nephropathy, focal and segmental glomerulosclerosis, minimal change disease, and karyomegalic-like interstitial nephritis were also described. Limitations: There was no systematic kidney biopsy performed for all patients with kidney injury after aHCT. Only a small proportion of patients with kidney damage underwent biopsy, making the results less generalizable. Conclusions: Kidney biopsy is useful in patients with kidney disease after aHCT to make a precise diagnosis and tailor therapy accordingly. This series is one of the few published studies describing pathologic findings of biopsies performed after aHCT in the context of acute kidney injury and chronic kidney disease. TMA was widely present on biopsy even when there was no clinical suspicion of such a diagnosis, suggesting that the current clinical criteria for a diagnosis of TMA are not sensitive enough for kidney-limited TMA.