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Bile cast nephropathy

      To the Editor: van Slambrouck et al.
      • van Slambrouck C.M.
      • Salem F.
      • Meehan M.M.
      • et al.
      Bile cast nephropathy is a common pathologic finding for kidney injury associated with severe liver dysfunction.
      report that bile casts are common in patients with severe liver dysfunction. They suggest that bile casts may account for renal dysfunction, but do not provide any compelling data to support this hypothesis. As this is an observational study, we believe that their conclusions should be guarded with caution.
      First, bile casts in these patients might merely reflect reduced glomerular filtration rate (GFR), interfering with the washout of casts, in the same fashion persistent nephrogram appears following radiocontrast administration in patients with contrast nephropathy or with reduced GFR from any other cause.
      • Sagiv I.
      • Koslowsky B.
      • Korem M.
      • et al.
      Scattered striated persistent nephrogram in sepsis.
      Second, bilirubin, a potent endogenous antioxidant, has been found to be renoprotective in experimental settings.
      • Nath K.A.
      Heme oxygenase-1: a provenance for cytoprotective pathways in the kidney and other tissues.
      Unexpectedly, rats subjected to bile duct ligation and developing billiary cirrhosis with ascites were found to be resistant to contrast nephropathy following COX and NOS inhibition, and their medullary thick limbs hardly developed hypoxic injury (unpublished data). This happened despite marked medullary thick limb hypertrophy, presumably with enhanced transport activity and oxygen consumption. In the same line, higher plasma bilirubin has recently been found to be associated with reduced risk for contrast nephropathy,
      • Huang S.S.
      • Huang P.H.
      • Wu T.C.
      • et al.
      Association of serum bilirubin with contrast-induced nephropathy and future cardiovascular events in patients undergoing coronary intervention.
      with improved renal graft survival, with preserved kidney function in IgA nephropathy, and with a better endothelial function and flow-mediated vasodilation.
      Thus, we suggest that bilirubin casts, noted in patients succumbing to liver failure and the hepatorenal syndrome, might reflect reduced GFR and diminished washout of casts, rather than play a role in the pathogenesis of this disorder.

      REFERENCES

        • van Slambrouck C.M.
        • Salem F.
        • Meehan M.M.
        • et al.
        Bile cast nephropathy is a common pathologic finding for kidney injury associated with severe liver dysfunction.
        Kidney Int. 2013; 84: 192-197
        • Sagiv I.
        • Koslowsky B.
        • Korem M.
        • et al.
        Scattered striated persistent nephrogram in sepsis.
        Nephrol Dial Transpl. 2011; 26: 2053-2055
        • Nath K.A.
        Heme oxygenase-1: a provenance for cytoprotective pathways in the kidney and other tissues.
        Kidney Int. 2006; 70: 432-443
        • Huang S.S.
        • Huang P.H.
        • Wu T.C.
        • et al.
        Association of serum bilirubin with contrast-induced nephropathy and future cardiovascular events in patients undergoing coronary intervention.
        PLoS One. 2012; 7: e42594