## **Core Concept**
The patient's presentation of acute abdominal pain, blood and mucous in the stool, and a palpable mass suggests an intestinal pathology, likely involving the lower gastrointestinal tract. The symptoms are indicative of an inflammatory or obstructive process.

## **Why the Correct Answer is Right**
The correct answer, **C. Intussusception**, is the most probable diagnosis given the combination of acute abdominal pain, the presence of blood and mucous in the stool (often described as "currant jelly" stool), and a palpable abdominal mass. Intussusception is a condition where a part of the intestine folds into the section next to it, often causing bowel obstruction and potentially cutting off blood supply. This condition is a common cause of intestinal obstruction and bleeding in children, particularly between the ages of 6 and 36 months, but can occur at any age.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While infections can cause abdominal pain and changes in stool, they less commonly present with a palpable mass.
- **Option B:** Although inflammatory bowel disease (IBD) can cause abdominal pain, blood in stool, and weight loss, a palpable mass is not a typical initial presentation.
- **Option D:** A Meckel's diverticulum can cause gastrointestinal bleeding, but it usually doesn't present with a palpable mass and acute abdominal pain simultaneously.

## **Clinical Pearl / High-Yield Fact**
A classic clinical presentation of intussusception is the triad of abdominal pain, vomiting, and bloody stools. However, this triad is present in only a minority of cases. The presence of a palpable mass is highly suggestive. Ultrasound is often used for diagnosis, showing a "target sign" or "pseudokidney" appearance.

## **Correct Answer:** C. Intussusception