Mesenteric cyst is a rare intra-abdominal cystic lesion located between the leaves of the mesentery, occurring in approximately 1 per 100,000-250,000 hospital admissions. Histologically, it represents a heterogeneous group encompassing different subtypes including lymphangioma, mesothelial cyst, enteric duplication cyst, enterogenous cyst, and dermoid cyst. The small bowel mesentery (ileal mesentery) is most commonly affected; however, it can also occur in the colon mesentery, omentum, and retroperitoneal space. Clinical presentation ranges from asymptomatic incidental detection to acute abdominal pain (torsion, rupture, infection). In children, it may present as abdominal distension and palpable mass, while in adults, it may present with vague abdominal pain or intestinal obstruction. On imaging, it appears as a thin-walled, unilocular or multilocular cystic mass; internal content may be serous, chylous, or hemorrhagic. In uncomplicated cysts, wall enhancement is minimal or absent; wall thickening and enhancement raise suspicion for infection or malignancy. Surgical excision (laparoscopic or open) is the gold standard treatment; recurrence rates up to 10% have been reported after incomplete resection.
Age Range
20-60
Peak Age
40
Gender
Equal
Prevalence
Rare
The pathogenesis of mesenteric cysts varies by subtype. Lymphangiomatous cysts (most common type, 60-70%) arise from failure of lymphatic tissue to connect to the venous system during embryological development; these aberrant lymphatic channels dilate and form cystic spaces. Lined by lymphatic endothelium, these cysts typically contain clear serous or chylous (triglyceride-rich milky-white) fluid. Chylous content reflects lymphatic drainage disruption connected to the thoracic duct or cisterna chyli. Mesothelial cysts originate from peritoneal mesothelium and their inner surfaces are lined by mesothelial cells; unlike peritoneal inclusion cysts, they possess a complete epithelial capsule. Enterogenous cysts arise from embryological gut duplication and are lined by intestinal mucosa; subtypes containing gastric mucosa carry risks of peptic ulceration and bleeding. Regarding imaging correlation: serous cysts show water density on CT (0-20 HU), chylous cysts show negative density (-10 to -20 HU, fat-like), and hemorrhagic cysts show high density (30-70 HU). On MRI, T1 signal varies with cyst content: serous cysts are T1 hypointense, hemorrhagic cysts are T1 hyperintense, and cysts with high protein content show intermediate T1 signal. All subtypes are T2 hyperintense but proteinaceous or hemorrhagic content can lower T2 signal.
The mesenteric claw sign is a pathognomonic morphological finding indicating that a cystic mass originates from between the mesenteric leaves. The mesenteric leaves open around the cyst creating a claw-like appearance; mesenteric vascular structures are seen stretched along the cyst wall. This finding confirms mesenteric origin and differentiates from retroperitoneal or bowel-origin masses. Portal venous phase best demonstrates this sign with contrast-enhanced mesenteric vessels.
On non-contrast CT, a thin-walled (<3 mm), well-defined cystic mass is seen between the mesenteric leaves. Internal density varies with cyst content: water density (0-20 HU) in serous cysts, negative density (-10 to -20 HU) in chylous cysts, and high density (30-70 HU) in hemorrhagic cysts. In multilocular variants, thin septa are visible with septal thickness generally <2 mm. Wall calcification is rare but thin peripheral calcifications may be seen after chronic inflammation. The mass displaces bowel loops laterally and anteroposteriorly; mesenteric vessels are stretched and displaced around the cyst (claw sign).
Report Sentence
Thin-walled, well-defined cystic mass between mesenteric leaves displacing bowel loops is consistent with mesenteric cyst; internal density value guides subtype.
In portal venous phase, cyst content shows no enhancement and remains at water/fat density. The thin cyst wall shows minimal or no enhancement — the most important indicator of benign cystic nature. In multilocular type, thin septa may show mild enhancement. Mesenteric arteries and veins are stretched and displaced around the cyst without vascular invasion. In complicated cysts (infection), wall thickening (>3 mm), irregular enhancement, and surrounding fat stranding may be observed.
Report Sentence
No enhancement of cyst content in portal venous phase confirms avascular cystic nature.
On T2-weighted images, a markedly hyperintense, homogeneous cystic mass within the mesentery is seen. In serous cysts, signal intensity equals free water with characteristic bright appearance. Chylous cysts may show slightly lower T2 signal due to triglyceride content but remain markedly hyperintense. Hemorrhagic cysts show variable signal depending on hemorrhage stage: acute T2 hypointense (deoxyhemoglobin), subacute T2 hyperintense (methemoglobin), chronic T2 hypointense peripheral rim (hemosiderin). Multilocular variant may show T2 hypointense thin septa.
Report Sentence
Markedly T2-hyperintense cystic mass within the mesentery with signal characteristics consistent with cystic content.
On T1-weighted images, mesenteric cyst signal varies with content. Serous cysts are T1 hypointense (water signal). Chylous cysts may show mild hyperintensity or intermediate signal due to fat content; signal loss on fat-suppressed sequences confirms chylous content. Hemorrhagic cysts show marked T1 hyperintensity due to subacute hemorrhage (methemoglobin). Mildly T1 hyperintense signal may be seen with proteinaceous content. The cyst wall is generally T1 hypointense.
Report Sentence
Mesenteric cystic mass shows variable T1 signal supporting content characterization.
On B-mode ultrasonography, an anechoic or hypoechoic, thin-walled, well-defined cystic mass is seen within the mesentery. Uncomplicated serous cysts are anechoic with posterior acoustic enhancement. Chylous cysts may show fine internal echoes (fat droplets). Hemorrhagic cysts show heterogeneous echogenic internal echoes and fluid-debris levels. Multilocular variant shows thin echogenic septa. The mass displaces bowel loops; no intracystic vascularity on Doppler.
Report Sentence
Anechoic, thin-walled cystic mass with posterior acoustic enhancement within the mesentery is consistent with mesenteric cyst.
On DWI, uncomplicated mesenteric cyst shows no diffusion restriction. At high b-values, intracystic signal is low with high ADC values (>2.0 × 10⁻³ mm²/s). In infected cysts, diffusion restriction due to purulent content — hyperintensity at high b-values and low ADC (<1.0 × 10⁻³ mm²/s) is the earliest MR finding of infection complication.
Report Sentence
Mesenteric cystic mass shows no diffusion restriction on DWI, consistent with uncomplicated cystic content.
Criteria
Most common subtype (60-70%). Multilocular cystic mass lined by lymphatic endothelium containing chylous or serous fluid. Results from embryological lymphatic development defect. Usually detected in childhood.
Distinct Features
Differentiated by multilocular structure. Negative CT density (-10 to -20 HU) is specific for chylous content. Chylous content shows signal loss on fat-suppressed MRI. High recurrence risk if complete resection is not possible; sclerotherapy (OK-432) is an alternative.
Criteria
Cyst lined by mesothelial cells, usually unilocular with serous content. Unlike peritoneal inclusion cyst, has a complete epithelial capsule. More common in adults. CT shows thin-walled unilocular cyst at water density.
Distinct Features
Unilocular structure and complete capsule differentiate from lymphangioma. Differentiated from peritoneal inclusion cyst by complete capsule. May be confused with simple ovarian cyst; mesenteric location differentiates. Surgical excision curative with low recurrence.
Criteria
Cyst lined by intestinal mucosa from embryological gut duplication. Most common at ileal level. Wall contains smooth muscle layer (gut signature — double-layered wall). Technetium-99m pertechnetate scintigraphy positive if gastric mucosa present.
Distinct Features
Adjacent location to bowel wall and 'double wall sign' (inner hyperechoic mucosa + outer hypoechoic muscularis) are diagnostic clues. Surgical indication stronger with gastric mucosa variant due to peptic ulceration risk. Shared vascular supply with adjacent bowel is critical for surgical planning.
Criteria
Hemorrhagic complication of any subtype. High density (30-70 HU) on CT, T1 hyperintensity on MRI. May present with acute abdominal pain.
Distinct Features
High CT density differentiates from simple cysts. T1 hyperintensity is specific for hemorrhage. Hemosiderin rim on gradient-echo sequences may be seen in chronic hemorrhage. Surgical treatment indicated.
Distinguishing Feature
Peritoneal inclusion cyst is usually pelvic and wraps around the ovary; wall formed by peritoneal adhesions without true epithelial capsule. Mesenteric cyst has complete capsule and is unrelated to ovary. Inclusion cyst shape conforms to organ contours (mold sign); mesenteric cyst is more round/oval. Inclusion cyst associated with pelvic surgery history.
Distinguishing Feature
Pseudomyxoma peritonei is characterized by diffuse mucinous ascites with peritoneal implants; scalloping pattern indents liver and spleen. Mesenteric cyst is localized, thin-walled without peritoneal implants. Mucinous material may have higher density and calcifications. Associated with appendiceal mucocele.
Distinguishing Feature
Omental lymphangioma is within the greater omentum anterior to bowel loops; mesenteric lymphangioma is between bowel loops. On MRI, both appear as multilocular T2 hyperintense cystic masses; anatomical location is the key differentiator.
Distinguishing Feature
Pancreatic pseudocyst is associated with pancreatitis history, located peripancreatic with pancreatic anatomical relationship and pancreatitis findings. Mesenteric cyst occurs without pancreatitis. Pseudocyst wall enhances due to granulation tissue; mesenteric cyst wall is very thin without enhancement.
Urgency
routineManagement
surgicalBiopsy
Not NeededFollow-up
6-monthMesenteric cyst is generally benign and malignant transformation is very rare. Conservative follow-up for asymptomatic small cysts (<5 cm); size monitoring with US or CT at 6-month intervals. Surgical excision (laparoscopic preferred) for symptomatic or >5 cm cysts; segmental bowel resection may be needed if bowel wall adhesion exists. Complications (torsion, rupture, infection) require emergency surgery. Recurrence up to 10% after incomplete resection. Pathological examination determines subtype and excludes rare malignant transformation.
Mesenteric cysts are usually asymptomatic. Surgical excision is curative for symptomatic or large cysts. Malignancy risk is negligible. Complications include torsion, infection, and bowel obstruction.