Mesenteric cysts are rare entities with varied presentations. Their estimated incidence in the general adult population ranges from 1 in 27,000 to 250,000—consequently most published studies consist of only a handful of cases1,2.
The earliest report of a mesenteric cyst was by the Florentine anatomist Benevieni in 1507, who described a “callus of messaric veins” during the post-mortem examination of an 8-year-old boy. Von Rokitansky described the first chylous cyst in 1842, and Gairdner in 1852 reported the first omental cyst. The earliest successful resection of a mesenteric cyst was described by Tillaux in 1880, and in 1883 Pean detailed a technique of marsupialising mesenteric cysts. Only 600 cases had been reported in literature by 19541,2,3.
Mesenteric cysts can arise within the mesentery of any part of the gastrointestinal tract, from duodenum to rectum. In a review series of 162 patients, 60% occurred in mesentery of small bowel, 24% in colonic mesentery, 14.5% arose in the retroperitoneum and the remaining 1.5% had uncertain origin1. These cysts are fluid-filled sacs lined with endothelium or mesothelium, and cysts ranging from 2 to 36 centimetres in diameter have been described in literature. These cysts may be uni-loculated, multi-loculated or septated, and can contain serous, chylous, sanguinous or chylolymphatic fluid. Other cysts may arise in the retroperitoneum but are considerably more difficult to manage although they can present in a similar manner1,4,5.
Correct pre-operative diagnosis is usually challenging and is typically reliant on clinical examination and radiological imaging. The condition is most common in the fourth decade of life, and patients can present asymptomatically or with non-specific abdominal pain, abdominal distension, nausea and vomiting, constipation or diarrhoea12. Symptoms are usually present for a period prior to clinical presentation, with a mean symptom duration of 6.6 months in one review1,2,3,8,11. Ultrasonography and computed tomography scans of the abdomen are favoured diagnostic modalities. Ultrasonography typically reveals a hypoechoic cystic mass and can also demonstrate septa, debris, abdominal fluid levels. Computed tomography scan allows for determination of size and occasionally the origin of the mass and its relation to neighbouring organs13.
The precise aetiology of mesenteric cysts has not been well established. Beahrs et al reported four main aetiologies of mesenteric cysts: developmental (enteric, urogenital, lymphoid and dermoid), infective (mycotic, tuberculous or parasitic) traumatic and neoplastic5. Mesenteric cysts can also be classified according to their histopathological findings into six groups: lymphatic origin (simple lymphatic cysts and lymphangiomas), mesothelial origin (simple mesothelial cysts, benign cystic mesotheliomas and malignant cystic mesotheliomas), enteric origin (enteric cysts and enteric duplication cysts), urogenital origin, mature cystic teratomas (dermoid cysts) and non-pancreatic pseudocysts (of traumatic or infectious origin)12,14.
The mesenteric cyst in our case report was a benign Mullerian cyst, which falls under the category of urogenital origin. Mullerian cysts are most commonly found in the vagina, uterus and ovaries in females, in the prostate and seminal vesicles in males, in the lumbosacral paravertebral region and rarely in the mediastinum15,16,17. Mullerian cysts arising in the mesentery are hence exceedingly uncommon, with only a few case reports published in literature15,18,19,20,21. Urogenital cysts are thought to be derived from vestiges of embryonic urogenital apparatus, and can be subclassified into: pronephric, mesonephric, metanephric and Mullerian18. Alternative mechanisms proposed include differentiation of coelomic epithelium or peritoneum into tubal type epithelium22. Mullerian cysts (also known as paramesonephric cysts) are embryological remnants of the caudal ends of fused Mullerian ducts, and are typically present if the Mullerian ducts fail to undergo complete agenesis in utero. In males, these ducts undergo full degeneration; while in females, the cephalad segments develop into the oviduct and the caudal segments fuse to form the uterus and upper vagina15.
The treatment of choice for mesenteric cysts is complete surgical excision – conventionally enucleation via an open approach, which also allows for simultaneous evaluation for other pathologies. More recently, successful resection by minimally invasive techniques has been described—the first report of laparoscopic enucleation was authored by Mackenzie in 1993. Laparoscopic resection of mesenteric cysts is increasingly gaining traction as an alternative approach to laparotomy, with cited benefits of reduced post-operative pain and analgesic requirement, shorter hospital stay, earlier return to daily activities and better cosmesis7. Aspiration or unroofing and marsupialisation of the cyst have been described in literature, but are generally not recommended if surgical excision is feasible because both of these options are associated with high risks of infection or recurrence3,4,8,9,10.
The risks of malignancy in mesenteric cysts reported in literature range from 3 to 22%1,2,5. Laparoscopic resection for larger mesenteric cysts invariably require aspiration for dissection from surrounding structures or extraction from the abdomen, with attendant risks of spillage of cystic contents into the peritoneal cavity7,11,23. An open procedure was chosen for the patient in our case report due to the size of the cyst—the main concerns were that of inadvertent spillage of cystic contents during aspiration and insufficient working space in the peritoneal cavity for laparoscopy. While open surgery is associated with disadvantages including increased pain when compared to a laparoscopic approach, this was managed with the use of regular oral paracetamol 1g every 6 hours and oral tramadol 50mg every 8 hours as required, as well as a continuous infusion of 2% ropivacaine local anaesthetic delivered at a rate of 7ml/hr into the pre-peritoneal plane via an ON-Q PainBuster® elastometric pump, inserted during wound closure at the end of the patient’s surgery. The patient did not require the use of strong opioids such as morphine and was fit for discharge 3 days after surgery on oral analgesia alone.