What is the Lesser Sac?

The lesser sac, also known as the omental bursa or bursa omentalis, is a potential space within the abdomen.

Understanding the Lesser Sac

The lesser sac is not an actual cavity but rather a potential space, meaning it's a space that can exist and may become apparent under certain conditions. According to the reference, it is located between the stomach and the pancreas. It's formed by the lesser and greater omentum, which are folds of peritoneum (the membrane lining the abdominal cavity).

Key Features of the Lesser Sac

• Location: Situated behind the stomach and in front of the pancreas.
• Formation: Created by the layers of the lesser and greater omentum.
• Nature: A potential space that can become a real space in the presence of fluid or other contents.
• Synonyms: Often referred to as the omental bursa or bursa omentalis.

How the Lesser Sac Forms

The lesser sac arises from the complex development of the abdominal organs and the peritoneum. It is essentially an invagination of the peritoneal sac. The greater omentum, a large apron-like fold, hangs down from the stomach and folds back on itself, creating the boundaries of this space. The lesser omentum, a smaller peritoneal fold, extends from the liver to the stomach.

Clinical Significance

Understanding the lesser sac's anatomy is essential in clinical practice for several reasons:

• Surgical procedures: It's an important landmark for surgeons during abdominal operations, especially those involving the stomach, pancreas, and surrounding areas.
• Spread of infection: Infections or inflammation within the abdomen can spread into the lesser sac.
• Fluid accumulation: Fluid can accumulate within the lesser sac, indicating underlying issues like pancreatitis or ascites.
• Tumor growth: Tumors in the adjacent organs can grow into or originate within the lesser sac.

Visualizing the Lesser Sac

While typically a potential space, the lesser sac can be visualized using imaging techniques such as:

• CT Scans: Helps visualize fluid, tumors, or other abnormal structures within the lesser sac.
• MRI: Provides detailed images of soft tissues and can identify pathologies within the sac.
• Ultrasound: Can be used to visualize fluid collections in the lesser sac.