## **Core Concept**
Peritonitis is inflammation of the peritoneum, typically caused by a bacterial infection. It can arise from various sources, including perforation of the gastrointestinal tract, allowing bacteria to spill into the peritoneal cavity. In adult males, the most common cause of peritonitis is related to the perforation of a viscus.

## **Why the Correct Answer is Right**
The correct answer, **C. Perforated peptic ulcer**, is the most common cause of peritonitis in adult males. This condition occurs when a peptic ulcer perforates through the stomach or duodenal wall, releasing acidic gastric contents and bacteria into the peritoneal cavity. This leads to a severe inflammatory response and infection. The perforation of a peptic ulcer is a surgical emergency requiring immediate intervention.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While **Spontaneous bacterial peritonitis (SBP)** is a known cause of peritonitis, it is more commonly associated with cirrhosis and ascites, rather than being the most common cause in adult males without specific risk factors like liver disease.
- **Option B:** **Appendicitis** can lead to peritonitis if the appendix ruptures. However, it is more commonly seen in younger individuals and is not the most frequent cause in adult males.
- **Option D:** **Diverticulitis** can also cause peritonitis, especially in older adults, but it is not the most common cause in adult males.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the most common causes of peritonitis can vary based on age, sex, and underlying health conditions. For adult males, a perforated peptic ulcer is a critical and life-threatening cause that requires immediate surgical evaluation. Recognizing the typical presentations and risk factors for these conditions can guide diagnosis and management.

## **Correct Answer:** C. Perforated peptic ulcer