Omental cyst

　　First, Etiology

　　The etiology may be related to the following factors:

　　1. Obstruction of a segment of the lymphatic vessels causes it to dilate and form a cyst.

　　2. The variation of embryonic cells in cysts can be formed by the proliferation of residual or ectopic embryonic tissue.

　　3. Traumatic hemorrhage is formed from the regression of a hematoma, possibly due to foreign body or surgical injury.

　　4. Inflammatory reaction False cysts are often secondary to inflammatory reactions, which can be the result of fat necrosis or other causes.

　　Second, Pathogenesis

　　Omental cysts are divided into true cysts and false cysts. True cysts are relatively rare, caused by abnormal development of congenital ectopic lymphoid tissue or lymphatic obstruction. The cyst wall is thin, lined with a single layer of endothelial cells, and can be unilocular or multilocular. The contents are mostly light yellow serous fluid and chyle-like fluid. False cysts are often secondary to traumatic hematoma, inflammation, fat necrosis, or foreign body reaction of the omentum. The cyst wall is thick, consisting only of fibrous tissue, without lining endothelial cells, mostly unilocular, containing turbid inflammatory exudate or blood.

　　This disease can cause intestinal obstruction due to the compression of the intestine by the omental cyst, and can cause incomplete intestinal obstruction. At the same time, due to the cystic usually being connected by connective tissue, after a meal, when there is intense activity, it can cause the pedicle of the cyst to twist and lead to severe abdominal pain. Secondly, this disease can cause diffuse peritonitis due to infection or rupture of the cyst, and infection entering the blood system can cause sepsis.

　　Small cysts generally have no clinical symptoms and are often found incidentally during laparotomy. Large cysts may have symptoms, characterized by abdominal distension and abdominal pain. Patients often discover a mass in the abdomen occasionally at night, feeling a heavy pressure in the abdomen when lying on their back. In cases of intestinal obstruction or torsion, severe abdominal pain may occur. Abdominal examination: A mass can be palpated in the abdomen, most often located in the upper abdomen, soft, with a cystic sensation, with a large range of motion, without tenderness or with deep-seated tenderness. Medium and small cysts located in the omentum have clear boundaries and are easily palpable, with a wide range of motion. Large cysts or those with complications are difficult to palpate and may be misdiagnosed as tuberculous peritonitis or ascites. In the supine position, the entire abdomen produces a dull sound when percussed, while only the flanks or腰部 present tympanic sounds. Intestinal sounds can be heard in the depth, and there is a sensation of water in the abdomen, but no mobile dullness.

　　The clinical manifestations of this disease vary depending on the size of the cyst and the presence of complications. It can be classified into 4 types:

　　1. Abdominal mass type:The abdomen can be clearly palpated without tenderness, with a large mobile cystic mass, which may be accompanied by abdominal dull pain or坠痛.

　　2. Pseudohydropic type:Only seen in giant omental cysts, with the abdomen gradually increasing in size, full abdominal distension, and inability to clearly palpate a mass. There is a significant liquid wave tremor, but no mobile dullness.

　　3. Hidden type:Mostly small cysts, discovered incidentally during abdominal surgery.

　　4. Acute abdomen type:When a cyst becomes twisted, there is internal hemorrhage, rupture, or secondary infection, it can cause acute abdominal pain and abdominal peritoneal irritation. After intracystic hemorrhage, the cyst rapidly increases in size, is prone to infection, and due to the majority of cysts being multilocular, infection is difficult to control. Patients may experience high fever or prolonged low fever, intermittent abdominal pain, lack of energy, poor appetite, weight loss, anemia, and other symptoms of consumptive intoxication. Clinically, it is very similar to tuberculous peritonitis and is easily misdiagnosed. Rupture of the cyst manifests as sudden severe abdominal pain after external force strikes the abdomen or due to an increase in intraperitoneal pressure for various reasons, accompanied by increased abdominal distension, marked anemia, and明显的血性或炎症性腹膜炎表现. It often resembles an acute abdominal condition and is admitted to the hospital. Cyst torsion occurs in the middle of the free margin of the omentum, in small cysts, with a wide range of movement. Due to gravity, cyst torsion causes persistent abdominal pain with periodic exacerbation, accompanied by nausea, vomiting, and physical examination findings of an abdominal mass, which is confirmed to be an omental cyst torsion after surgery.

　　This disease may be caused by obstruction and expansion of a segment of the lymphatic vessels to form a cyst, or by the proliferation of residual or ectopic embryonic tissue, which can also be formed by hematoma regression due to traumatic hemorrhage. It may also be caused by foreign bodies or surgical injuries. Additionally, pseudocysts are often the result of inflammatory reactions, which can be the result of fat necrosis or other causes. Therefore, the etiology is diverse, and preventive measures should be targeted at the etiology. Increasing exercise to enhance physical fitness can help reduce the incidence of the disease.

　　Firstly, Laboratory examinations

　　During acute abdominal pain, most patients may exhibit an increased peripheral white blood cell count.

　　Secondly, Imaging examinations

　　1. Abdominal X-ray flat film:Visible abdominal shadow of soft tissue mass filled with liquid, with calcification in dermoid cysts, and structures such as bones and/or teeth sometimes present.

　　2. Barium meal examination:There may be signs of small intestinal displacement or compression, with the small intestine shifted to the posterior superior abdomen and sides of the spine, the stomach upwardly displaced, and a significant widening of the distance between the anterior abdominal wall and the small intestine. Barium enema examination shows the transverse colon shifted upward, and the ascending and descending colon shifted laterally and outwardly.

　　3. Ultrasound examination:It is the preferred examination method. If it can show a cystic mass that is close to the anterior abdominal wall, with clear boundaries and easily displaced by the probe in all directions, and clearly distinguishable from the liver, spleen, pancreas, kidney, and ovary, it is of great value for the diagnosis of this disease. Considering that this examination is simple, fast, and painless, it is particularly practical for the diagnosis of omental cysts with torsion or internal hemorrhage.

　　4. Arterial angiography of the abdomen:The image shows the extension and encasement of the omental artery and its branches around the cyst, providing direct and strong evidence for the diagnosis of this disease.

　　5. Laparoscopy:The mass can be directly visualized.

　　1. The diet should be light, and it is not suitable to eat mutton, shrimp, crabs, eels, salted fish, black fish, etc. Foods that are suitable for light diets should be eaten.

　　2. Suitable foods include milk, spinach, yam, cabbage, rapeseed, mushrooms, lean meat, eggs, crucian carp, apple, pear, jujube, peanuts, black rice, etc.

　　3. The diet should be rich in nutrition, correct malnutrition and abnormal eating habits, and it is not advisable to eat刺激性, seafood, etc. frequently.

　　4. Eat more lean meat, chicken, eggs, quail eggs, grass carp, turtle, white fish, cabbage, asparagus, celery, spinach, cucumber, winter melon, mushrooms, tofu, fruits, etc.

　　I. Treatment

　　Once an omental cyst is confirmed, surgical treatment should be performed, and aspiration therapy under ultrasound or CT guidance is not recommended. For solitary small cysts, complete excision should be performed. When the cyst is adherent to the stomach and intestines and cannot be separated, it is generally advisable to excise the involved part together. However, for giant lymphangiomas that are extensively adherent to the small intestine, partial cystectomy can be performed to avoid extensive small intestinal resection. If there are intervals in the remaining part, they should be trimmed as close to the wall as possible to open them up. Afterward, 3% iodine tincture should be used to rub the remaining cyst wall to destroy the inner membrane.

　　After the excision of omental cysts, the small omentum, gastrocolic ligament, gastrosplenic ligament, and mesocolon should be carefully examined for the presence of cysts to avoid missing any. For giant cysts, fluid should be gradually aspirated and decompressed before excision to prevent a sudden and significant drop in abdominal pressure, which can affect heart, lung function, and hemodynamic balance, posing a risk to life. After the excision of a large cyst, it is necessary to use an abdominal binder for a longer period of time to prevent the sagging of abdominal organs and the abdominal wall.

　　II. Prognosis

　　The prognosis after excision of omental cysts is good.