A 40-year-old patient complains of chronic pain abdomen and diarrhea. She gives history of passing 22-25 stools per day. She also complains of weight loss. On examination, patient is noted to have mild fever with right lower quadrant tenderness. Lower GI endoscopy was done with the following findings: HPE reveals the following findings: An intern posted in the medicine ward makes a list of differential diagnosis for this patient. Which of the given option is most likely the diagnosis?

**Core Concept**
The patient's symptoms, including chronic abdominal pain, diarrhea (with a high frequency of 22-25 stools per day), weight loss, and mild fever, suggest a diagnosis of a gastrointestinal disorder with an infectious or inflammatory etiology. The right lower quadrant tenderness points towards a specific region of the gastrointestinal tract being involved.

**Why the Correct Answer is Right**
The patient's symptoms are highly suggestive of an ileal involvement, likely due to a bacterial infection. The high frequency of diarrhea is consistent with a toxin-mediated illness, where the bacteria produce a heat-stable toxin that causes increased intestinal secretion and fluid loss. The ileum is the primary site of absorption of vitamin B12 and bile salts, which may contribute to the patient's weight loss and malabsorption symptoms. The presence of mild fever indicates an inflammatory component to the disease.

**Why Each Wrong Option is Incorrect**
* **Option A:** Ulcerative colitis typically presents with bloody diarrhea, mucosal ulcers on endoscopy, and left lower quadrant tenderness, which does not match this patient's presentation.
* **Option B:** Crohn's disease can present with similar symptoms, but it often involves the terminal ileum and may cause fistulas, strictures, or abscesses, which were not mentioned in the patient's history.
* **Option C:** Irritable bowel syndrome (IBS) is characterized by chronic abdominal pain, changes in bowel habits, and bloating, but it does not typically cause fever, weight loss, or the high frequency of diarrhea seen in this patient.

**Clinical Pearl / High-Yield Fact**
The patient's symptoms are consistent with a diagnosis of traveler's diarrhea, which is often caused by enterotoxigenic Escherichia coli (ETEC). This bacterium produces a heat-stable toxin that causes increased intestinal secretion and fluid loss, leading to the characteristic symptoms of traveler's diarrhea.

**Correct Answer:** D.

✓ Correct Answer: B. Crohn disease