What is the Difference Between Peritoneal and Retroperitoneal?

The peritoneum and retroperitoneum are both located in the abdominal cavity, but they refer to different spaces and the organs they protect and nourish.

Peritoneal refers to the space within the peritoneum, which is a double-layer sheet that protects the organs in the abdominal cavity. The peritoneum consists of two layers: the parietal peritoneum and the visceral peritoneum. Intraperitoneal organs are directly visible and accessible after opening the peritoneal cavity.

Retroperitoneal refers to the space containing organs found behind the peritoneum and separated from the peritoneum by the parietal peritoneum. Retroperitoneal organs are not associated with visceral peritoneum; they are only covered in parietal peritoneum, and that peritoneum only covers their anterior surface. Retroperitoneal structures can be further subdivided into two groups based on their embryological development:

• Primarily retroperitoneal organs developed and remain outside of the parietal peritoneum. Examples include the esophagus, rectum, and kidneys.
• Secondarily retroperitoneal organs were initially intraperitoneal, suspended by mesentery. Through the course of embryogenesis, they became retroperitoneal as their mesentery fused with the posterior abdominal wall. Examples include the ascending and descending colon.

In summary, the main differences between peritoneal and retroperitoneal are:

• Peritoneal refers to the space within the peritoneum, while retroperitoneal refers to the space behind the peritoneum.
• Peritoneal organs are directly visible and accessible after opening the peritoneal cavity, while retroperitoneal organs are not.
• Peritoneal organs are covered by both parietal and visceral peritoneum, while retroperitoneal organs are only covered by parietal peritoneum.

Comparative Table: Peritoneal vs Retroperitoneal

Here is a table summarizing the differences between peritoneal and retroperitoneal spaces:

The peritoneal space contains organs such as the stomach, spleen, liver, and parts of the intestines, while the retroperitoneal space contains organs such as the ureters, suprarenal glands, and kidneys. The peritoneum is a continuous membrane that lines the abdominal cavity and covers the abdominal organs, providing support and protection. The retroperitoneal organs, on the other hand, are not associated with visceral peritoneum and are only covered by parietal peritoneum on their anterior surface.