A 30-year-old male patient presented to the hospital with left lower abdominal pain, bloody diarrhea, and weight loss for the past three days. On examination, he had slight tenderness in the left iliac fossa. His symptoms, lab results, and colonoscopy findings were consistent with a diagnosis of ulcerative colitis. Ulcerative colitis is an autoimmune disease that causes inflammation of the colon's mucosal lining and is characterized by diarrhea, rectal bleeding, abdominal pain, and weight loss. Treatment involves medications like 5-aminosalicylic acid to reduce inflammation of the intestinal lining.