Introduction
-Pathology of the mesentery is rare and represents an heterogeneous group of lesions.
-Different components of the mesentery can be at the origin of pathology ( peritoneum,
lymphatic tissue,
fat and connective tissue).
-Proliferation of the pathology can be tumoral ,inflammatory or infectious.
-During this presentation they will be classified as solid or cystic tumors,
malignant or benign.
I.
Cyst mass :
Tumoral cystic mass:
Before the interpratation of any cystic mass an intraperitoneal localized reactive effusion (result of pancreatitis,
perforation or bile peritonitis ….) should be eliminated.
Especially fluid collections in the lesser sac can simulate a cystic mass.
- Lymphangioma
It develops from the lymphatic system and results from a defect of connecting of lymphatic channels and development of lymphangiectasia, then cystic masses.
-The content is serous or Chylous.
- A malignant transformation is described in 3% of cases. This is the most common of mesenteric cystic tumors.
-Most lymphangiomas are located in the neck,
but 5% of lymphangiomas are abdominal.
CT description :
- Cystic mass of the mesentery low density uni or multiloculated.
- Lymphangioma has enhancing septa.
- Unlike in cystic peritoneal metastases,
ascites is not a feature of lymphangioma.
---->When you see a septated cystic lesion without ascites the most likely diagnosis is a lymphangioma.
2.Peritoneal Inclusion Cyst
=Multilocular peritoneal inclusion cyst = Benign cystic mesothelioma.
It develops from the peritoneum.
But has no relation with the malignant mesothelioma.
It occurs premenopausal women with prior gynaecological surgery or infection
CT description :
- It has to be located in the pelvis
- Multicystic pelvic mass
- Enhancing septa
- Peritoneal surfaces of uterus,
bladder
- May extends into upper abdomen
This description is not specific but the pelvic localisation is suggestive .
--- >transvaginal ultrasound could be usfully : demonstrating a multicystic pelvic lesion next to the uterus,
which proved to be a peritoneal inclusion cyst.
3.Mucinous Carcinomatosis
Peritonealcarcinomatosis: occurs in high-grade mucinousneoplasm (gastrointestinaltract,gallbladder,
pancreas,
ovary… ).
And can be complicated espacially with a bowel obstruction.
CT description :
- Abnormal low attenuation loculated fluid throughout the peritoneal cavity associated with scalloping of the liver and splenic surfaces as well intraperitoneal organs.
- Abnormal soft tissue mass is seen studded over the omentum.
- The primary tumour could be objectified.
- It is associated with enlargedlymph nodules , tumor nodules along the peritoneal lining ,
omental tumor.
4.Pseudomyxoma peritonei
It is an intraperitoneal accumulation of a gelatinous ascites secondary to rupture of a mucinoustumor.
A typical feature of pseudomyxoma peritonei is scalloped indentation of the surface of the liver and spleen ,
without significant invasion of underlying tissue.
CT description:
- Mucinous material has low density and appears heterogeneous.
- Scalloped surface of the liver,
spleen,
and mesentery.
- Rim-like calcifications are common.
- Undersurface of the diaphragm may be thickened by large cystic masses of mucinous tumor.
- Peripheral location of tumor within the abdomen with central displacement of the small bowel and mesentery.
Non Tumoral cystic mass
1.
Nonpancreatic Pseudocyst
It is a residual of an old hematoma or abcess .
Radiologist should look for an history of trauma or infection.
CT description :
- Thickened wall and there can be some debris within the lesion.
- You can suggest this diagnosis when you have a positive history and you see this thickened wall or debris.
2.Tuberculosis Fig. 1,
Fig. 2
•This infection can produce very thick ascites,
that can be loculated in distribution.
Because of this,
it can simulate a cystic lesion.
We can find other signs such as Lymph nodes with low attenuation or thoracic localisation.
3.Echinococcal Cyst Fig. 3,
Fig. 4
It is unusual for an echinococcal cyst to be located in the peritoneum.
It favors the liver,
the spleen and even the kidney over the peritoneum.
CT description:
- cystic mass,unior multiloculated with individualized wall,
sometimes calcified.
- Radiologist should look for an abdominal localisation associated.
4.Enteric cyst and mesothelial cyst
•They are rare and have nonspecific imaging features.
•It could be confused with lymohangioma.
II.
Solid mass:
1.Lymphoma Fig. 5,
Fig. 6
Lymphoma represents the most frequent malignant mesenteric tumors.
It is in the majority of the cases Non hodgkin Lymphoma.
CT description :
- A common finding imaging is termed the “sandwich sign” .
- The mesenteric fat and tubular vascular structures serve as the “filling,” and the homogeneous soft tissue masses serve as the “sandwich bun.”
- The bulky adenopathy of lymphoma is unique,
which makes the sandwich sign specific to mesenteric lymphoma.
•Mesenteric lymphoma is typically asymptomatic until large,
enveloping fat,
bowel and vessels without causing significant clinical
2.Peritoneal metastases
Peritoneal metastases are the most common peritoneal solid masses.
Gastrointestinal and ovarian cancers are the most common etiologies.
CT description :
- Thickening and enhancement of peritoneal reflections (especially if nodular).
- Soft tissue nodules.
- Stranding and thickening of the omentum (omental cake).
- Stranding and distortion of the small bowel mesentery.
- Ascites,
especially if loculated.
3. Desmoid tumour
-Fibroblastic proliferation,developed from the fascia and the Aponeurosis.
-Their evolution is characterized by a local aggresivity and tendency to recurrence, without metastatic potential
-Small bowel mesentery is the most common site.
13% of patients have familial adenomatous polyposis (FAP) Or Gardner syndrome.
CTdescription
- Wellcircumscribed entirely tissue mass, not wrapped, usually homogeneous and slightly.
- enhanced by contrast and sometimes in heterogeneous way.
- Larger than 10 cm, the multiplicity tumors,
infiltration, or the invasion of the mesentery.
4.Carcinoid Fig. 9,
Fig. 10,
Fig. 11
-Carcinoid is a slow-growing neuroendocrine tumour most commonly found in the small bowel.
-Carcinoid metastasizes localized in the mesentery,
which at times is easier to appreciate than the primary tumor in the small bowel. There is associated bowel wall thickening.
CT description :
- CT with injection described a not well limited,
infiltrative,
associated with mesenteric mass calcifications .
-The octreoscan,
which is positive in 85% of carcinoids,
so this can be a great help in the differential diagnosis.
This is often the case because the primary tumor can be quite small.
5.Gastrointestinal Stromal Tumor - GIST
-Primary small bowel tumors can extend into the mesentery and the typical example of that is the GIST.
- It is a mesenchymal tumour derived from the cells of Cajal.
CT description :
- It is an often heterogeneous mesenteric mass
- they have mixed density due to necrosis and hemorrhage and they tend to be well vascularized.
6.Inflammatory Pseudotumor
-This disease can affect lung,
orbit and mesentery.
-Inflammatory pseudotumor is a diagnosis by exclusion.
-Usually the diagnosis is made at surgery or biopsy.
It is the result of chronic inflammation with an unclear pathogenesis.
7.Sclerosing Mesenteritis
-This disease has multiple synonyms reflecting the wide histologic spectrum: mesenteric panniculitis,
fibrosing mesenteritis and mesenteric lipodystrophy.
Pathologically it is a chronic inflammation of unknown etiology.
This form is mostly named panniculitis mesenterialis.
-In a more advanced stage you can have significant fibrosis resulting in retraction of the small bowel.
Within these masses dystrophic calcifications can be seen as well as lucent areas of fat
CT description :
- A solid mass of the mesentery enveloping the vessels,
sometimes responsible for collateral circulation.
- Tow important features are the persistence a greasy Halo around the vessels (fat-ring-sign) and the presence in 50% of cases of a pseudocapsule.
8.Actinomycosis Fig. 13,
Fig. 12
-Actinomycosis is a subacute-to-chronic bacterial infection caused in 70% by to either Actinomyces israelii or A.
gerencseriae.
-It is characterized by contiguous spread,
suppurative and granulomatous inflammation,
and formation of multiple abscesses.
In women,
pelvic actinomycosis is possible.
CT description :
- The masses are of solid appearance (pseudotumors) moderately enhanced after injection of contrast product.
- This presentation would be the most frequent compared to the cystic aspect,
with thick wall and enhanced by contrast .
- This peripheral enhancement,
although not specific to actinomycosis,
is highly suggestive of inflammation.
- This multicompartmental mass or not is often accompanied by a densification of mesenteric fat punctiform or radially