Figure 1. Abdominal computed tomographic scan with oral and intravenous contrast showing fluid displacing posteriorly the centrally located and clumped intestinal loops.
Laparoscopy was performed and revealed a massive omental cyst containing about 200 mL of blood-tinged fluid occupying the entire peritoneal cavity. A cystectomy was performed, and findings from histopathologic examination showed an intraperitoneal lymphatic cyst.
In ascites there is abdominal distension, pouting of the umbilicus, scrotal swelling, and bulging flanks with fluctuation, shifting dullness, and a fluid wave on palpation. The chemical and hematological characteristics of ascitic fluid help in establishing an etiological diagnosis (portal hypertension, hypoalbuminemia, infection, chyle, and urinary or gastrointestinal tract leaks). Atypical of ascites in the patient we describe was the absence of flank bulging, the posterior displacement of intestinal loops on findings from abdominal ultrasonography and computed tomography, and the hazy yellow appearance of the fluid obtained by paracentesis in the absence of clinical or biochemical evidence of liver disease.
Mesenteric cysts, with sizes varying from a few centimeters to more than 30 cm in diameter, may occur in the ileal or small bowel mesentery, the root of the mesentery with retroperitoneal extension, the transverse mesocolon, or the gastrocolic ligament. When they are located anterior to the intestine, they are called omental cysts. Unilocular or multilocular, they often contain chylous fluid. A thin wall, internal septations, and an endothelial lining are characteristic of the cysts.1 They are caused either by gradual enlargement of lymphatic spaces because of obstruction of the lymphatic channels or by congenitally atopic lymphatic tissue that does not communicate with the vascular system. Approximately one third of patients with these lesions are children.
The rarity of these lesions and lack of characteristic clinical features may present diagnostic difficulties. Most cases are asymptomatic. The clinical presentation relates to size, location, and complications, such as bowel obstruction, perforation, peritonitis, volvulus, or malignant degeneration. Presenting symptoms include abdominal distension, pain, and vomiting, mimicking appendicitis or an acute abdomen.2- 4 A painless, asymptomatic, compressible, and freely movable abdominal mass may be the mode of presentation. Mesenteric cysts may cause complete or partial intestinal obstruction or torsion of the small bowel.5,6 A hemorrhagic or ruptured mesenteric cyst following trauma7- 9 is an abdominal emergency.
As reported in this case, giant mesenteric cysts mimic ascites with abdominal distension, shifting dullness, and the presence of a fluid wave, but a useful distinguishing clinical characteristic is the absence of flank bulging.10- 12 Ultrasonography is the diagnostic method of choice and demonstrates the appearance of well-defined, anechoic masses, loculations, or septated ascites. An omental cyst appears as a well-outlined, sonolucent, transonic abdominal mass. Computed tomography is reserved for atypical cases.
Complete cyst resection is the treatment of choice. Partial bowel resection is required in some cases. Laparoscopic surgery is performed in selected cases when the preoperative diagnosis is certain. Mesenteric cysts should be considered in the differential diagnosis of abdominal distension, mass or pain, acute abdomen, ascites, or bowel obstruction.
Accepted for publication January 24, 1999.
Reprints: Hassib Narchi, MD, FRCP, FRCPCH, Paediatric Department, Sandwell General Hospital, Lyndon, West Bromwich, B71 4HJ, West Midlands, England (e-mail: firstname.lastname@example.org).
Radiological Case of the Month. Arch Pediatr Adolesc Med. 2000;154(9):958. doi: