**Question:** Backwash ileitis is seen in

A. Crohn's disease
B. Ulcerative colitis
C. Inflammatory bowel disease (IBD)
D. Celiac disease

**Correct Answer:** D. Celiac disease

**Core Concept:**

Backwash ileitis is a clinical entity characterized by inflammation of the terminal ileum and its adjacent areas, caused by the backwash of inflammatory substances from the adjacent inflamed regions, typically in the setting of Inflammatory Bowel Disease (IBD). In this context, IBD encompasses both Crohn's disease (CD) and ulcerative colitis (UC).

**Why the Correct Answer is Right:**

Celiac disease (CD) is an autoimmune disorder triggered by ingesting gluten in genetically susceptible individuals. In CD, the ingestion of gluten leads to an immune response causing damage to the small intestine's mucosal lining. However, CD primarily affects the small intestine, not the terminal ileum.

**Why Each Wrong Option is Incorrect:**

A. Crohn's disease (CD) is another IBD characterized by transmural inflammation involving any part of the gastrointestinal tract. CD can certainly present with backwash ileitis, making this option incorrect.

B. Ulcerative colitis (UC) is another IBD affecting the colon and rectum, not the terminal ileum, making this option incorrect.

C. IBD encompasses both CD and UC, but the correct answer is CD as it is the one that can present with backwash ileitis.

**Clinical Pearl:**

Backwash ileitis can be a manifestation of IBD, particularly CD, due to the backwash of inflammatory substances from the inflamed segments of the gastrointestinal tract. It is essential for clinicians to consider this possibility in patients presenting with terminal ileitis, as early recognition can lead to appropriate diagnosis and management.