Omental cyst is a rare disease, accounting for about 50% of all mesenteric cysts.

bubble_chart Pathogenesis

Membrane cysts can be divided into two types: primary and secondary:

1. Primary (true) cysts are congenital and form during the embryonic period.

2. Secondary (pseudo) cysts are mostly caused by various inflammatory reactions in the abdominal cavity, such as post-traumatic hematomas or fat necrosis. Their cystic fluid is relatively turbid or bloody.

bubble_chart Pathological Changes

Cystic masses are formed due to congenital developmental abnormalities or acquired obstruction of the lymphatic system in the greater omentum. They are generally multilocular but can also be unilocular. The cysts can grow very large, and the cystic fluid is usually clear serous lymph. Over 80% of the cyst walls are lined with endothelium, while dermoid cysts are extremely rare and may contain various components such as skin and hair. If caused by trauma or complicated by torsion, intracystic hemorrhage may occur, turning the cystic fluid bloody or brownish-yellow. In very rare cases, the fluid may be purulent. Although trauma and fat necrosis contribute to the formation and development of certain pseudocysts, the cause of most cysts remains unknown.

bubble_chart Clinical Manifestations

Small cysts usually have no clinical symptoms and are often discovered incidentally during other abdominal surgeries. Large cysts often cause abdominal distension, fullness, and dull pain. Patients may notice them accidentally when lying flat, feeling a soft abdominal mass. They can also cause abdominal discomfort, a sense of heaviness, and dull pain. Sometimes, extremely large cysts may occupy the entire abdominal cavity. Physical examination may occasionally reveal a poorly defined mass.

Abdominal B-ultrasound can detect cysts and compression of adjacent organs, but it cannot confirm an omental cyst. X-rays may show fluid-filled masses in the abdomen compressing internal organs, but they also cannot confirm the diagnosis. It is often misdiagnosed as a mesenteric cyst before surgery.

bubble_chart Treatment Measures

Multilocular omental cysts should be excised together with the omentum. Unilocular small cysts can be separated and removed from the adipose tissue. Omental cysts are prone to complications such as intracystic hemorrhage or torsion. Once these occur, the cyst rapidly enlarges, presenting with abdominal pain and/or peritoneal irritation signs, requiring prompt surgical removal.

bubble_chart Prognosis

The prognosis after membrane cyst excision is good, with rare recurrence.

bubble_chart Differentiation

This disease needs to be differentiated from ascites, subcutaneous nodular peritonitis, mesenteric tumors, and giant ovarian cysts.