Leaving colitis untreated can lead to severe complications, including the risk of colon perforation, which is a life-threatening condition where a hole forms in the colon wall. Patients may also develop toxic megacolon, characterized by rapid swelling and potential rupture of the colon. Furthermore, untreated colitis increases the risk of colon cancer due to chronic inflammation and can heighten the likelihood of developing other inflammatory diseases, such as arthritis or skin disorders. Early diagnosis and management are crucial to prevent these serious health outcomes.