Giuliani KTK, Kassianos AJ, Kildey K, et al. - Researchers investigated the cellular as well as the molecular pathophysiology of human bile cast nephropathy (BCN). For this purpose, they used immunohistochemistry (IHC) to stain paraffin‐embedded sections of renal biopsy tissue from a BCN patient. They compared quantitative analyses of IHC staining vs healthy renal cortical tissue. The BCN case was characterized by yellow to brown granular casts, consistent with the presence of bile pigment. Strong tubular 4‐hydroxynonenal staining intensity, a marker of oxidative stress, was evident in relation to the presence of bile pigment. Experts found diffuse tubulointerstitial inflammatory cell infiltrate, with elevated CD1c (dendritic cells), CD68 (macrophages) and CD3 (T cells) staining. Overall, it was suggested, for the first time ever, that bile casts may cause oxidative stress as well as trigger the inflammasome signalling cascade, resulting in interstitial inflammation and driving acute kidney injury pathobiology.