**Core Concept**
Lymphocytic colitis is a type of microscopic colitis characterized by an increase in intraepithelial lymphocytes (IELs) in the colonic mucosa. This condition is often associated with non-bloody, watery diarrhea.

**Why the Correct Answer is Right**
Intraepithelial lymphocytes are a hallmark feature of lymphocytic colitis. The condition is diagnosed by the presence of increased numbers of IELs in the colonic epithelium. This is typically assessed through histopathological examination of colonic biopsies. The increased IELs are thought to play a role in the pathogenesis of the condition, although the exact mechanisms are not fully understood. The presence of IELs is a key distinguishing feature from other forms of microscopic colitis, such as collagenous colitis.

**Why Each Wrong Option is Incorrect**
**Option A:** Bloody diarrhea is more commonly associated with collagenous colitis, another type of microscopic colitis, rather than lymphocytic colitis.
**Option C:** Lymphocytes in stools are not a specific diagnostic feature of lymphocytic colitis; rather, the diagnosis is made through histopathological examination of colonic biopsies.
**Option D:** Peyer's patches are not typically associated with lymphocytic colitis; they are more commonly found in the small intestine and are involved in immune function.

**Clinical Pearl / High-Yield Fact**
Lymphocytic colitis and collagenous colitis are two distinct forms of microscopic colitis, and their diagnosis relies on the presence of specific histopathological features. A high index of suspicion and careful histopathological examination are essential for accurate diagnosis.

**✓ Correct Answer: B. Intra epithelial lymphocytes**