## **Core Concept**
The question tests the ability to diagnose acute abdomen in a patient with prolonged fever, which could indicate an infectious or inflammatory process. The acute onset of abdominal pain and distension, along with tenderness and guarding, points towards a surgical abdomen.

## **Why the Correct Answer is Right**
The correct answer, **Typhoid perforation**, is a well-known complication of untreated or undertreated typhoid fever, especially in areas where typhoid is common. Typhoid fever, caused by *Salmonella Typhi*, can lead to intestinal perforation in the third week of illness due to ulceration of Peyer's patches in the intestine. This condition presents with acute abdominal pain, tenderness, guarding, and often, signs of peritonitis. The prolonged fever (15 days) fits with the timeline for typhoid fever complications.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While **Appendicitis** can present with acute abdominal pain and tenderness, it typically doesn't have a prolonged fever before the onset of abdominal pain. Appendicitis can perforate, leading to peritonitis, but the history of prolonged fever doesn't strongly suggest appendicitis.
- **Option B:** **Intestinal obstruction** can cause abdominal distension and pain but usually doesn't present with prolonged fever. It can have a variety of causes, including mechanical obstruction or ileus, but fever isn't a primary presenting symptom.
- **Option C:** This option seems to be missing but based on the context, if it were another condition like **Diverticulitis** or a different diagnosis, it would likely not fit as well with the prolonged fever history and acute presentation of pain and distension.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that **typhoid perforation** is a classic cause of acute abdomen in areas endemic for typhoid fever, particularly if the patient has had untreated or undertreated typhoid fever. A high index of suspicion is crucial in such cases, especially with a history of prolonged fever.

## **Correct Answer:** D. Typhoid perforation