My Father Is 72 Years Old And Has Type 2

My father is 72 years old and has type 2 diabetes. He went to the bathroom last night and large amounts of blood and water gushed out. My mom took him to the ER today and he was admitted. They are doing a colonoscopy tomorrow morning. He complained of severe abdominal pain when they pressed on his stomach. What do you think is wrong? They recently took him off a medicine that was causing his stomach to be upset.