Recent studies have identified several promising biomarkers—syndecan-1 (SDC1), neutrophil gelatinase-associated lipocalin (NGAL), proenkephalin (PENK), and presepsin (PSPN)—that have shown diagnostic and prognostic potential in critical care settings, although their comparative value in S-AKI prediction and outcome assessment continues to be refined. The gene discussed is PENK; the disease is acute kidney injury.