In the hydrated state (A), contrast is filtered and passes into the tubule lumen but does not accumulate and is not reabsorbed. Consequently, the inflammasome in infiltrating leukocytes is not stimulated, and there is insufficient immune activation to induce a prolific leukocyte infiltration and strong inflammatory response. In contrast (B), in the volume-depleted state, filtered contrast accumulates in the tubule lumen and is reabsorbed, resulting in stimulation of infiltrating leukocytes in addition to resident macrophages, leading to a massive influx of leukocytes and an excessive inflammatory response that ultimately precipitates AKI. DPEP-1, dipeptidase-1.