**Core Concept:** Right Iliac Fossa Pain, Neutrophilia, and Abdominal Ultrasound Findings

A 25-year-old female presents with acute abdominal pain and tenderness in the right iliac fossa, along with raised neutrophil count. The absence of a history of tuberculosis and normal X-ray abdomen rules out certain possibilities, leaving us with a narrowed differential diagnosis. An ultrasound abdomen is performed and shows focal wall thickening and peristalsis disturbance in the cecum and ascending colon.

**Why the Correct Answer is Right:**

The correct diagnosis is **Option D:** Crohn's Disease. Crohn's Disease is a type of inflammatory bowel disease (IBD) that can affect any part of the gastrointestinal tract, but it commonly presents with abdominal pain, tenderness in the right iliac fossa, and a history of diarrhea, weight loss, and malabsorption. In this case, the patient's pain and tenderness are in the right iliac fossa, which is a characteristic presentation of Crohn's Disease affecting the terminal ileum. The raised neutrophil count is also suggestive of an inflammatory process.

The abdominal ultrasound findings of focal wall thickening and peristalsis disturbance in the cecum and ascending colon are indicative of inflammation and bowel wall thickening, which are common in Crohn's Disease. The absence of tuberculosis in the patient's history and normal X-ray abdomen rules out other differential diagnoses like appendicitis, which would typically show periappendicular inflammation and gas under the right costal margin on X-ray.

**Why Each Wrong Option is Incorrect:**

**Option A:** Ulcerative Colitis is another IBD, but it typically affects the colon and rectum, resulting in a more diffuse rather than focal wall thickening on ultrasound.

**Option B:** Pancreatic enzymes and amylase are elevated in acute pancreatitis, not neutrophilia. Tenderness in the right iliac fossa is also less specific in pancreatitis.

**Option C:** Infectious enterocolitis may present with abdominal pain, but the focal wall thickening and peristalsis disturbance in the cecum and ascending colon are more consistent with Crohn's Disease. Additionally, the patient has no history of diarrhea, weight loss, or malabsorption, which are more common in infectious enterocolitis.

**Option E:** Chronic appendicitis would typically show periappendicular inflammation and gas under the right costal margin on X-ray, which is not mentioned in the patient's history or examination findings.

**Clinical Pearls:**

1. The combination of abdominal pain, focal wall thickening, and tenderness in the right iliac fossa in a young patient (typically below 40 years) without a history of diarrhea, weight loss, or malabsorption is more suggestive of Crohn's Disease.
2. Focal wall thickening and peristalsis disturbance in the cecum and ascending colon is more consistent with Crohn's Disease than