**Question:** Which is true of Ulcerative colitis:

A. It affects the small intestine.
B. It is characterized by inflammation of the colon.
C. It is primarily a pediatric disease.
D. It is a rare condition.

**Core Concept:** Ulcerative colitis is a type of inflammatory bowel disease (IBD) that primarily affects the colon and rectum, causing chronic inflammation and ulceration of the gastrointestinal tract. IBD includes two main types: Crohn's disease and ulcerative colitis.

**Why the Correct Answer is Right:**
B. Ulcerative colitis is characterized by inflammation of the colon (large intestine). This is a key feature that distinguishes it from Crohn's disease, which can affect any part of the gastrointestinal tract from the mouth to the anus.

**Why Each Wrong Option is Incorrect:**
A. Ulcerative colitis does not affect the small intestine; it primarily affects the colon.
C. Ulcerative colitis is not primarily a pediatric disease; it can affect both adults and children. However, Crohn's disease is more common in children and young adults.
D. Ulcerative colitis is not a rare condition; it is relatively common, affecting approximately 1 in 200-500 people in the general population.

**Clinical Pearl:** Understanding the differences between ulcerative colitis and Crohn's disease is crucial for appropriate diagnosis and management of IBD patients. Both disorders share common symptoms, such as abdominal pain, diarrhea, and weight loss, but they differ in their distribution and extent of involvement. Ulcerative colitis typically presents with continuous inflammation along the colon, whereas Crohn's disease can involve any part of the gastrointestinal tract and often presents with skip lesions (areas of normal mucosa between affected areas).

**Correct Answer:** B. Ulcerative colitis is characterized by inflammation of the colon.