An autopsy case with tubular obstruction by impacted swollen blebs due to ischemic acute kidney injury.

Abstract

Background: Oliguric acute kidney injury (AKI) is one of the critical conditions which needs emergent treatment due to the lack of the capacity of excreting toxins and fluids, and plasma membrane bleb formation is considered as one of the characteristic morphologic alterations in ischemic AKI in both animal models and human. We present here an autopsy case with clear electron microscopy images capturing a definitive instance of blebbing in ischemic AKI.

Case presentation: A 66-year-old man was admitted for oliguric AKI with nephrotic syndrome (NS). Because of the existence of hematuria with red blood cell casts and rapid deterioration of renal function and severe systemic symptoms such as loss of appetite and general fatigue, we started immunosuppressive therapy with steroids, considering a vasculitis-like condition with NS, and hemodialysis was also started for oliguria. However, he suddenly died of hemorrhagic shock due to gastric ulcer. Histological findings of the kidney by autopsy showed segmental sclerosis and acute tubular necrosis (ATN) in paraffin sections, which suggests that this is the case with ATN showing oliguric AKI as a clinical presentation. Interestingly, in electron microscopical study, not only apical membrane blebbing but also numerous cytoplasmic bodies were observed in proximal tubules (PT), and this bleb formation was also observed as foamy blebs in the Toluidine blue stained Epon section, where it appeared to fill the tubular lumen.

Conclusion: Our distinct finding of bleb formation with tubular obstruction strongly indicates that blebbing could be related to the mechanism of oliguric AKI in human, which supports the tubular obstruction theory as a contributing factor to the pathogenesis of ischemic AKI.