Fujigaki Y, et al. - Herein, the mechanisms of acute kidney injury (AKI) in adult minimal change nephrotic syndrome (MCNS) patients were assessed. In MCNS patients without renal dysfunction, the existence of proximal tubular injuries with increased urinary N-acetyl-β-D-glucosaminidase (uNAG) was reported, with more severity noted in the AKI group vs in the non-AKI group. The unique tubular injuries possibly ascribed to massive proteinuria might represent a factor that predisposes for the development of severe AKI in adult MCNS patients.

Methods

• This study was performed on a total of 37 adult MCNS patients.
• Researchers retrospectively analyzed clinical data and tubular cell changes using the immunohistochemical expression of vimentin as a marker of tubular injury and dedifferentiation at kidney biopsy.
• For defining AKI, the criteria of the Kidney Disease was used: Improving Global Outcomes (KDIGO) Clinical Practice Guidelines for AKI.

Results

• Data showed that, at kidney biopsy, 13 patients (35.1%) were designated with AKI.
• Researchers found that AKI and non-AKI groups did not differ significantly in terms of age, history of hypertension, chronic kidney disease, diuretics use, proteinuria, and serum albumin.
• In both groups, increased urinary N-acetyl-β-D-glucosaminidase (uNAG) and urinary alpha1-microglobulin (uA1MG) were noted as markers of tubular injury, but the levels were found to be significantly increased in the AKI group vs the non-AKI group.
• A comparable incidence of vimentin-positive tubules was reported between AKI (84.6%) and non-AKI (58.3%) groups, but in the AKI group (19.8%) vs the non-AKI group (6.8%) (p=0.011), significant increase was noted in the vimentin-positive tubular area per interstitial area.
• Furthermore, in both groups, vimentin-positive injured tubules with tubular simplification (loss of brush-border of the proximal tubule/dilated tubule with flattening of tubular epithelium) were observed in the vicinity of glomeruli, indicating injury to the proximal convoluted tubules, in particular.
• Results also revealed that 2 patients had relatively severe tubular injuries with vimentin positivity and needed dialysis within 2 weeks following kidney biopsy.
• In the non-AKI group, a positive correlation of the percentage of the vimentin-positive tubular area with uNAG but not with uA1MG was observed.