**Core Concept**
Peritonitis is a severe inflammation of the peritoneum, the thin layer of tissue that lines the abdominal cavity, often caused by bacterial infection. This condition can lead to various complications, including organ dysfunction, sepsis, and even death if left untreated.

**Why the Correct Answer is Right**
Peritonitis often causes a cascade of events that can lead to severe complications. However, one complication that is not typically seen with peritonitis is the formation of an **aneurysm**. Aneurysms are abnormal dilations of blood vessels that can occur due to various factors, including atherosclerosis, trauma, or infections like endocarditis. Peritonitis primarily affects the peritoneum and surrounding organs, but it does not directly cause vascular wall damage leading to aneurysm formation.

**Why Each Wrong Option is Incorrect**
* **Option A:** Sepsis is a well-known complication of peritonitis, characterized by a systemic inflammatory response to an infection. Sepsis can lead to organ dysfunction and failure if not promptly treated.
* **Option B:** Abscess formation is a common complication of peritonitis, where a collection of pus forms in the abdominal cavity, often requiring surgical drainage.
* **Option D:** Intestinal obstruction can occur as a complication of peritonitis, particularly if the infection leads to adhesions or scar tissue formation that blocks the normal flow of intestinal contents.

**Clinical Pearl / High-Yield Fact**
When managing a patient with peritonitis, it is essential to consider the potential for complications such as sepsis, abscess formation, and intestinal obstruction. Prompt recognition and treatment of these complications can significantly improve patient outcomes.

**Correct Answer:** D.