Omental cyst torsion is a clinical manifestation of omental cysts. Omental torsion refers to the twisting of the greater omentum along its longitudinal axis and causes its blood circulation to become impaired. It is generally classified as primary or secondary. The torsion is often clockwise and can be twisted multiple times. What can cause omental cysts? I. Pathogenesis Its etiology may be related to the following factors: 1. obstruction of a segment of the lymphatic vessels and enlargement to form a cyst. 2.Variation of embryonic cells: cysts can develop from the proliferation of leftover or ectopic embryonic tissues. 3. Injurious bleeding: degeneration from a hematoma, which may be a foreign body or surgical injury. 4.Inflammatory reaction: pseudocysts mostly occur after inflammatory reaction and can be the result of fat necrosis or due to other causes. Second, the pathogenesis of large omental cysts are divided into two categories: true cysts and pseudocysts. True cysts are rare and are caused by abnormal development of congenital ectopic lymphoid tissue or obstruction of lymphatic vessels. The cysts are thin-walled, covered with a single layer of endothelial cells, and may be single- or multi-housed, and the contents are mostly pale yellow plasma and celiac fluid. Pseudocysts are mostly secondary to traumatic hematoma, inflammation, fat necrosis or foreign body reaction of the greater omentum. Its cyst wall is thick, only fibrous tissue, no lining endothelial cells, mostly single room, containing cloudy inflammatory exudate or blood. Gastrointestinal barium meal X-ray can reveal small intestine displacement and compression signs, which are not easily distinguished from mesenteric masses. Dermatomal cysts are occasionally seen as calcifications or structures such as teeth and bones. Ultrasound helps to determine whether the cyst is unicompartmental or multicompartmental, but it needs to be differentiated from mesenteric cysts, retroperitoneal cysts and ovarian cysts, which are seen on ultrasound to move up and down with breathing and the small intestine to move to the retroperitoneal wall. Intravenous pyelogram helps to differentiate from retroperitoneal cysts. CT scan is best for exact localization, but the source of the cyst is not easily identified by CT either. Abdominal arteriography is also available and can show images of the greater omental artery and its branches extending and encircling the cyst. Surgical exploration is often required for final confirmation of the diagnosis.