Chronic inflammation is prolonged inflammation that can last weeks to years. It involves ongoing tissue destruction and attempts at repair through fibrosis. It can follow acute inflammation or result from persistent infections like tuberculosis. Common features include mononuclear cell infiltration of macrophages, lymphocytes and plasma cells, as well as proliferative changes like angiogenesis and fibrosis. Chronic inflammation can be non-specific or granulomatous, characterized by granulomas which form to contain hard to eliminate agents and involve epithelioid cells, giant cells, and caseous necrosis. Examples include chronic cholecystitis and pyelonephritis.