The mesentery is a continuous fold of tissue that attaches the small and large intestines to the back wall of the abdomen, holding them in place and supplying them with blood vessels and nerves. A mesenteric cyst is a fluid-filled sac that develops within this tissue. This condition is exceedingly rare, occurring in approximately 1 out of every 100,000 to 250,000 hospital admissions. Although these cysts are uncommon and often benign, their presence raises concerns about potential danger and necessary medical intervention.
What Are Mesenteric Cysts
Mesenteric cysts are cystic lesions found anywhere in the mesentery, from the duodenum to the rectum, though they occur most frequently in the small intestine. They are extremely rare, with fewer than 1,000 cases reported in medical literature since 1507. These cysts can be simple, containing a single chamber, or multilocular, having multiple internal compartments.
Their origin is varied, leading to classification based on lining cells and fluid content. The most common types are of lymphatic origin, such as lymphangiomas, which arise from congenital malformations of lymphatic tissue. Other classifications include cysts of enteric, mesothelial, or urogenital origin, alongside non-pancreatic pseudocysts resulting from trauma or infection.
How Symptoms Present
Mesenteric cysts are often discovered incidentally during imaging or surgery for an unrelated condition. Approximately 40% of cases are detected this way because the cyst is asymptomatic. When symptoms do occur, they are typically vague, mimicking other common gastrointestinal issues.
Common complaints include generalized or intermittent abdominal pain, nausea, and abdominal distension. A soft, mobile mass may sometimes be felt during a physical examination. Symptom severity is linked to the cyst’s size and location; a large cyst is more likely to cause noticeable abdominal swelling or pressure effects on surrounding organs.
Evaluating the Risk of Complications
The danger associated with a mesenteric cyst is primarily mechanical, stemming from its potential to grow large enough to interfere with normal organ function. While the cysts themselves are rarely malignant, they pose a threat when acute complications arise. These complications occur in about 10% of patients and often require emergency surgical intervention.
Acute Mechanical Risks
One concerning complication is torsion, where the cyst twists on its axis, often involving the segment of the intestine it is attached to. This twisting cuts off the blood supply to the bowel, leading to tissue death and a severe abdominal crisis.
Another acute risk is spontaneous or traumatic rupture of the cyst, which can spill its contents (chylous, serous, or infected) into the abdominal cavity, potentially causing peritonitis.
A large cyst can also cause a mechanical bowel obstruction by pressing on or kinking the adjacent loops of the intestine. Obstruction can lead to vomiting, severe distension, and the inability to pass stool. Less frequent complications include internal hemorrhage into the cyst or secondary infection, both causing acute pain and systemic symptoms.
Malignancy Risk
The risk of a mesenteric cyst being or becoming malignant is extremely low, reported in less than 3% of cases. This possibility necessitates comprehensive evaluation and supports definitive treatment upon diagnosis.
Diagnosis and Management
The diagnostic process begins when a mass is detected during physical examination or seen on imaging performed for other reasons. Ultrasound is often the initial imaging modality, confirming the cystic nature and determining if it is unilocular or multilocular.
Cross-sectional imaging, such as a CT scan or MRI, is then used to define the cyst’s exact location, size, and relationship to surrounding organs and major blood vessels. This detailed imaging is crucial for surgical planning, particularly in identifying whether the cyst is intertwined with the blood supply of the adjacent bowel.
Management depends on the cyst’s size, symptoms, and the patient’s overall health. Small, entirely asymptomatic cysts may sometimes be monitored through watchful waiting, especially if found in elderly patients with complex medical issues. However, due to the lifelong risk of acute mechanical complications like torsion or obstruction, surgical intervention is generally recommended for nearly all patients.
The standard procedure is complete surgical excision, often performed using minimally invasive laparoscopic techniques. The goal is enucleation—peeling the cyst away from the mesentery while preserving the blood supply to the bowel. If the cyst is deeply integrated with the blood vessels, a segment of the bowel may need to be removed along with the cyst to ensure complete removal and prevent recurrence. Following successful surgical removal, the prognosis is excellent, and recurrence is rare.