Mesenteric Lymphangioma

Mesenteric lymphangioma (cystic lymphatic malformation) is a benign, multiloculated lymphatic malformation arising from sequestered lymphatic channels that fail to connect with the venous system. Most are diagnosed in childhood, and 60 to 70% present before age 5, although adult cases occur. Abdominal lesions are about 5% of all lymphatic malformations (the head and neck and axilla are the usual sites).

Pathology: thin-walled cysts lined with flat endothelium, lymphoid aggregates and smooth muscle in the wall, with straw-colored, milky (chylous) or bloody content. Immunohistochemistry is positive for D2-40 and CD31. Somatic PIK3CA mutations are found in many, which explains the response to PI3K and mTOR pathway inhibitors.

Natural history: slow growth, with sudden enlargement after infection, trauma or hemorrhage. The lesion rarely regresses and does not become malignant. Complications are obstruction, volvulus, infection, hemorrhage, rupture, chylous ascites, protein-losing enteropathy and compression of vessels.

• Painless abdominal distension or a mass, or an incidental finding
• Intermittent colicky pain, vomiting, constipation and weight loss
• Acute abdomen from volvulus, hemorrhage, infection or rupture
• Chylous ascites with distension and shifting dullness
• Red flags: fever with a tender mass, bilious vomiting, peritonitis, and hemodynamic compromise

1. Ultrasound: a multiseptated cystic mass with thin walls, and debris or fluid-fluid levels from hemorrhage. Doppler shows no flow in septa.
2. MRI: high T2 signal in the lobules, with T1 hyperintensity in chylous or hemorrhagic components. It defines the extent in the mesentery and retroperitoneum and the relation to vessels.
3. CT with contrast: a multiloculated fluid-attenuation mass with thin septa that enhance slightly.
4. Diagnostic aspiration (if the diagnosis is unclear): chylous fluid with triglycerides over 1.1 mmol/L (100 mg/dL) and lymphocytic predominance.
5. Histology after excision confirms the diagnosis.

Differentials: mesenteric cyst of other origin, cystic teratoma, lymphoma, duplication cyst, pancreatic pseudocyst, ovarian cyst, mesothelioma, sarcoma.

1. Observation for small, asymptomatic lesions, with ultrasound every 6 to 12 months.
2. Complete surgical excision (the definitive therapy): laparoscopic or open, with dissection from the mesenteric vessels. Bowel resection with anastomosis when vessels cannot be preserved. Cefazolin 2 g IV with metronidazole 500 mg IV before incision (children: cefazolin 30 mg/kg and metronidazole 7.5 mg/kg). Recurrence is under 5% after complete excision and up to 30% after incomplete excision or marsupialization.
3. Percutaneous sclerotherapy for macrocystic lesions or when surgery is hazardous: aspirate the fluid, then instill doxycycline 10 mg/mL (maximum 20 mg/kg) or bleomycin 0.5 mg/kg (maximum 15 units) or OK-432 (0.1 to 0.2 mg per session), and repeat at 4 to 6 weeks for 2 to 4 sessions. Complications are fever, pain, infection and sclerosant leakage. Microcystic disease responds poorly.
4. Sirolimus for extensive, inoperable or recurrent disease: 0.8 mg/m2 orally twice daily, adjusted to a trough level of 10 to 15 ng/mL. Monitor lipids, blood counts, liver function and wound healing, and give trimethoprim-sulfamethoxazole 160/800 mg orally three times weekly as prophylaxis against Pneumocystis infection. Avoid live vaccines. Alpelisib is an option in PIK3CA-related disease.
5. Chylous ascites: a low-fat diet with medium-chain triglycerides, octreotide 100 micrograms SC three times daily, and paracentesis when symptomatic.
6. Infected cyst: antibiotics (ceftriaxone 2 g IV daily with metronidazole 500 mg IV every 8 hours) then drainage or resection once settled.

Follow-up with ultrasound or MRI at 6 and 12 months, then annually for 3 years. Counsel on symptoms of obstruction and infection.