Mesenteric cysts

Mesenteric cysts are rare, fluid-filled lesions that originate in the mesentery. The cause is often unclear but may be congenital or secondary to lymphatic obstruction, trauma, or inflammation. Many cysts are asymptomatic and discovered incidentally but some manifest with nonspecific abdominal symptoms such as chronic abdominal pain, nausea, vomiting, and/or a palpable mass. Diagnosis is based on imaging (i.e., ultrasound, CT, and/or MRI) and histology findings (required for definitive diagnosis). Complete surgical excision is the treatment of choice and is associated with an excellent prognosis; recurrence and malignant transformation are rare.

• Mesenteric cyst: a cyst that originates within the mesentery ^[2]
• There are multiple types of mesenteric cysts, including:
  • Peritoneal simple mesothelial cyst (PSMC)
  • Chylolymphatic mesenteric cyst
  • Cystic lymphangioma
  • Enteric duplication cyst
  • Enteric cyst
  • Nonpancreatic pseudocyst (e.g., cerebrospinal fluid pseudocyst, lymphocele)

• Incidence: ∼ 1 in 250,000 hospital admissions ^[3]
• Affected population varies by cyst type, e.g.: ^[1]
  • PSMC: typically seen in children and young adults
  • Chylolymphatic mesenteric cyst: primarily affects adults (♀ > ♂)
  • Cystic lymphangioma
    • (♂ > ♀)
    • Most common in children; sometimes seen in adults

Epidemiological data refers to the US, unless otherwise specified.

Mesenteric cysts can be classified based on cause (e.g., congenital, reactive) or histological subtype, e.g.: ^[1][3]

• Lymphatic (e.g., cystic lymphangioma, simple lymphatic cyst)
• Mesothelial (e.g., PSMC)
• Enteric (e.g., enteric cyst, enteric duplication cyst)
• Urogenital
• Mature cystic teratoma (mesenteric dermoid cyst)
• Nonpancreatic pseudocyst

• Often asymptomatic and discovered incidentally in ∼ 40% of cases ^[3]
• Symptoms are typically nonspecific and may include: ^[3]
  • Chronic abdominal pain
  • Palpable abdominal mass
  • Nausea and vomiting
  • Symptoms of bowel obstruction

General principles ^[1][3]

• Cross-sectional imaging is essential for diagnosis.
• Appearance varies based on cyst type.
• Histological evaluation is required for a definitive diagnosis.

Imaging ^[1][3]

Modalities

• Ultrasound
  • May show septations and/or abdominal fluid
  • Not ideal for large or complex cysts
• CT: Findings may help identify the cyst type.
  • Fluid-fluid levels
  • Calcifications in the cystic wall
• MRI: high sensitivity and specificity for assessing cyst size and relationship to adjacent structures

Findings by subtype ^[1]

• PSMC
  • Unilocular
  • Thin-walled
  • No septations
• Chylolymphatic mesenteric cyst
  • Unilocular
  • Contains a fluid-fluid level with nondependent chyle
• Cystic lymphangioma
  • Typically multiseptated
  • Contrast enhancement of cyst wall and septa
• Enteric duplication cyst
  • Findings are best evaluated on ultrasound.
  • Gut signature sign (characteristic): Cyst wall contains all five layers of the gastrointestinal wall.
• Enteric cyst
  • Findings are best evaluated on ultrasound.
  • Cyst wall does not contain all layers of the gastrointestinal wall.
  • Contains a single, disorganized outer muscle layer
• Nonpancreatic pseudocyst
  • Thick-walled lesion with progressive mural enhancement (due to fibrous wall tissue)
  • May contain a fluid-fluid level
  • May show inflammatory changes

• Ovarian cyst
• Abdominal abscess
• Peritoneal inclusion cyst
• Cystic lesions arising from other abdominal or pelvic organs, e.g.:
  • Biliary hamartoma
  • Pancreatic cystic lesions
• Neoplastic lesions, e.g.:
  • Neoplasm with cystic degeneration (e.g., neuroendocrine tumor)
  • Mucinous cystic neoplasm of mesentery
  • Gastrointestinal stromal tumor
  • Sarcoma
  • Desmoid tumor
• Mesenteric lymph nodes (e.g., due to tuberculosis)

The differential diagnoses listed here are not exhaustive.

• Complete surgical excision via laparoscopy or laparotomy (first-line for most cysts)
• Segmental bowel resection (enterectomy) may be required if the cyst is adherent to the intestine or its vascular supply.
• Pseudocysts are typically managed with drainage and/or marsupialization.

• Bowel obstruction
• Volvulus
• Complication within the cyst, e.g.:
  • Torsion
  • Rupture
  • Hemorrhage
  • Infection
• Compression of surrounding organs

We list the most important complications. The selection is not exhaustive.

• Prognosis is excellent with complete surgical excision.
• Malignant transformation occurs in ∼ 3% of cases. ^[3]