The presence of high concentrations of fibrin degradation products, plasminogen activator, kallikrein, interleukin-6, platelet-activating factor, fibroblast growth factor and vascular endothelial growth factor in postoperative drainage was associated with a higher rates of hematoma recurrence.[21,22] Postoperative drainage may accelerate the excretion of residual subdural hematoma and brain expansion, and therefore may contribute to early recovery of motor and cognitive function, followed by improved daily activities and self-care. Here, KLK4 is linked to hematoma.