A 16-year-old boy with a history of appendicitis presents with abdominal pain, malaise, weight loss, and bloody diarrhea. The nurse practitioner suspects ulcerative colitis (UC). What is the pathophysiology of UC?

Choice A reason: This describes the pathophysiology of gastroesophageal reflux disease (GERD), not ulcerative colitis. UC affects the colon, not the esophagus. Choice B reason: This explanation pertains to peptic ulcer disease, where H. pylori and NSAIDs disrupt gastric mucosal defenses. It does not apply to UC, which is an inflammatory bowel disease. Choice C reason: These factors may influence general gastrointestinal health or contribute to irritable bowel syndrome (IBS), but they do not explain the autoimmune and inflammatory nature of UC. Choice D reason: Ulcerative colitis is characterized by chronic inflammation of the colon due to defects in the epithelial barrier, dysregulated immune responses, abnormal leukocyte trafficking, and altered gut microbiota. These mechanisms lead to mucosal ulceration, bleeding, and systemic symptoms.