Pediatric large omental cyst is a rare disease with low incidence, non-specific clinical manifestations, difficult diagnosis itself, and even rarer when it leads to acute abdomen, mostly found incidentally during surgery, with a high rate of preoperative misdiagnosis. From March 2007 to October 2008, two children with large omental cysts were admitted to our hospital with acute abdominal disease, and we report them as follows.
1 Clinical data
Male, 3 years old, diagnosed as “intestinal spasm and intestinal obstruction” three times in one year in a foreign hospital, this time admitted with “abdominal pain and vomiting for 2 days”, on examination: abdomen flat, periumbilical pressure pain, not fixed, no rebound pain, local abdominal muscle tension, but no No obvious mass was found. Preliminary diagnosis: intestinal obstruction. The abdominal pain was relieved by itself, and the effect of non-surgical treatment was not obvious.
Female, 4 years old, had a history of periumbilical pain for more than one year, without any obvious history of abdominal trauma. Preliminary diagnosis: acute peritonitis purulent appendicitis with perforation. Ultrasound examination showed: multiple cystic masses in the abdomen with separation. Dissection revealed: ruptured large omental cyst.
2 Discussion
2.1 Clinical features
Large omental cysts can be divided into true cysts and pseudocysts. True large omental cysts are more common in pediatric patients and can be of histological types such as lymphovascular-derived cysts, enteric-derived cysts, and mesothelial cysts. Among them, lymphovascular-derived cysts are the most common, mostly due to obstruction of the large omental lymphatic vessels, causing enlargement of the lymphatic network, or from the development of ectopic lymphatic tissue that is not connected to the vascular system. The etiology of large omental cysts is not well understood; the original lymphoid tissue remains to form the cyst wall, which secretes lymphatic fluid and collects to form cysts that are not connected to the normal lymphatic vessels. The incidence is 1/11250 of hospitalized patients[1] . The disease usually occurs in pediatric patients with a mean age of 4.9 years[2] . Large omental cysts, whether solitary or multiple, are distributed on the blood-rich large omentum, and when the cyst wall is thin and under little tension, the cyst moves like a pseudopod in the abdominal cavity and does not compress the gastrointestinal tract, thus generally without clinical symptoms. However, under certain conditions, such as special positions, exercise, and trauma, acute abdomen can occur, and in 1964 Oliver first reported the risk of acute abdomen in large omental cysts, with torsion and infection as the most common complications [3]. Those who present with acute abdomen are mainly due to local intestinal tube compression by large omental cysts, cyst tip torsion, intracapsular hemorrhage, infection, and rupture.
2.2 Clinical manifestations
1. the abdomen gradually increases in size, and abdominal pain, intestinal obstruction, fever and dyspeptic manifestations may occur in a few cases.
2. on palpation, the abdomen is a cystic mass with relatively clear borders and large mobility.
3. when torsional bleeding occurs it rapidly becomes larger and harder in texture with severe abdominal pain.
The majority of cases of large omental cysts have no clinical symptoms and are mostly found incidentally on radiological and pathological examination, with frequent abdominal pain manifested only in children [4]. In the present group of cases, all had a history of recurrent abdominal pain, which was periumbilical, vague, tolerable, and relieved on its own.
2.3 Diagnosis and differentiation
Diagnostic points.
1 When the cyst is large, there may be vague abdominal pain, abdominal distension, a feeling of heaviness, and an abdominal mass.2 On examination: a large mobile, painless mass with a smooth, cystic surface is found in the upper or middle abdomen.3 A barium X-ray examination reveals a mass in front of the intestinal canal, with compression or displacement of the intestinal canal.4 Color ultrasound: a multi-room or single-room cystic lesion with a fluid-free echogenic area. In combination with infected bleeding, there may be scattered echogenic dots or clusters with floating movement with body position.5 CT examination: a large low-density mass with a thin cystic wall is its typical presentation, located in the anterior abdomen, with the small intestine often pushed to one side and prone to bleeding and torsion [5].
Differential diagnosis.
The disease should be differentiated from ascites, tuberculous peritonitis, intestinal spasm, and appendiceal perforation; it should also be differentiated from abdominal cystic diseases, such as mesenteric cysts, ovarian cysts, intestinal duplication malformations, and pseudopancreatic cysts.
2.4 Misdiagnosis and countermeasures
Because of the lack of characteristic symptoms and signs of this disease, clinical diagnosis is difficult and the correct preoperative diagnosis rate is low, so
It is very important to fully understand the characteristics of the disease, symptoms and complications arising from the size of the cyst, and to reduce misdiagnosis. (1) In patients with occult abdominal pain, further examination cannot be stopped when symptoms can be seen to be relieved and there are no positive signs on physical examination. Although physical examination can reveal a cystic painless mass with smooth surface, I believe that large omental cysts with thin and soft walls, cystic fluid density close to water and no tension, when examined after lying down, the cystic fluid can quickly lay flat with the intestinal tube depression and move by intestinal peristalsis, and it is not easy to detect the presence of cysts by feel alone. So the necessary auxiliary examination is especially important for the correct diagnosis of this disease. (2)Spiral CT examination is very necessary when cystic mass or ascites is diagnosed by ultrasound, especially when huge type of cyst fills the whole abdomen and it is not easy to detect liquid level reflection wave by ultrasound, and sometimes it is difficult to distinguish it from ascites.CT can accurately observe cyst shape, size, intracapsular fluid density, relationship with surrounding organs and large blood vessels, and has high diagnostic and differential diagnostic value [6]. (3) The disease is easily misdiagnosed as tuberculous peritonitis, and there are many reports of anti-tuberculosis treatment [7]. When it is difficult to differentiate between the two, blind puncture and aspiration should not be avoided to avoid rupture of the cyst, leading to acute peritonitis. (4) During dissection for suspected purulent appendicitis, if appendiceal inflammation is found to be incompatible with signs of peritonitis, the possibility of large omental cyst torsion should be thought of; if there is a lot of peritoneal fluid and light appendiceal inflammation, the possibility of large omental cyst rupture and rupture of cyst fluid into the abdominal cavity should be thought of.
Therefore, clinicians should learn more about rare diseases, increase their knowledge, broaden their horizons, examine the body carefully, and choose appropriate auxiliary examinations to reduce misdiagnosis on the basis of mastering common and multiple diseases.