MP is a benign, tumor-like mesenteric lesion, formed as result of chronic inflammation of adipose tissue; the etiology is unknown. In the literature, the disease is named with a number of synonyms: mesenteric lipodystrophy and sclerosing or retractile mesenteritis, each of which is a histologic variant based on the relative amounts of inflammation, fat necrosis and fibrosis [1
]. While a large series of cases of small-bowel MP has been reported [1
], this process rarely involves the mesentery of the large intestine, as was observed in this case.
MP has a slight male predominance and commonly occurs in late adulthood [1
]. The symptoms of the disease are varied, and mostly include intermittent abdominal pain (34.6%), presence of abdominal mass (30.8%), nausea/vomiting, weight loss, bowel habit changes, with or without fever [1
]. In the study by Akram et al. [4
], common symptoms included abdominal pain in 70% of cases, diarrhoea in 25% and weight loss in 23%. Symptoms associated with MP can be caused by direct mechanical effects of the abdominal mass encasing the bowel, blood vessels and lymphatics, which can result in partial bowel obstruction [8
], ischemia [6
] or chylous ascites [17
]. As recently reported by Van lingen et al. [14
], MCP should be considered as a possible cause of unexplained colitis but can also manifest as ischemic colitis. The mechanism of ischemic colitis is thought to be secondary to venous insufficiency as opposed to arterial ischemia as evidenced by the absence of thrombosis of mesenteric arteries [13
]. We hypothesize that severe edema of the mesocolon and mesosigmoid related to MCP induced venous ischemia which caused ischemia of the sigmoid mucosa. In the article by Akram et al. [4
], 14% of MP patients were found to have chylous ascites, as was also the case in our observation. The reported clinical presentation of MP of the small intestinal mesentery or the large intestine is not significantly different. Generalized weakness with weight loss and severe bowel dysfunction are symptoms described in both [8
]. Usually, the diagnosis of MP is made after several months’ history of recurrent abdominal pain, continuing weight loss, altered bowel habits and the presence of a palpable abdominal mass [11
]. However, it is important to recall that most cases of MP (up to 92% in the study by Daskalogiannaki et al. [5
]) are asymptomatic and are incidentally detected on abdominal CT performed for unrelated conditions.
Abdominal CT and magnetic resonance imaging (MRI) play important roles in suggesting the accurate diagnosis and can be used to distinguish MP from other diseases with similar imaging features such as carcinomatosis, carcinoid tumor, lymphoma or desmoid tumor. The “fat ring sign” (preservation of the densitometric values of fat near the mesenteric vessels) and the finding of “tumor pseudocapsule” (hyper-attenuated stripe partly surrounding the mass) are considered to be suggestive of mesenteric involvement [18
]. However, in some cases, the differential diagnosis (Lymphoma / Carcinoid tumors / Desmoid tumors / Carcinomatosis / Peritoneal mesothelioma / Retroperitoneal sarcoma / Amyloidosis / IgG4-related retroperitoneal fibrosis / Infectious diseases (including tuberculosis, histoplasmosis and Whipple’s disease) / Reaction to adjacent or chronic abscess / Chronic inflammation due to foreign body) cannot be narrowed by imaging alone and biopsy with histological analysis is required.
A recent study by Zissin et al. [19
] suggested that positron emission tomography (PET) with 18 FDG may be used to differentiate between benign and neoplastic processes of the mesentery. According to the authors, PET can be used to correctly exclude mesenteric tumor involvement when no FDG uptake was observed associated with typical CT features of MP. However, a recent case report [17
] described a patient with symptoms and CT findings of MP and a negative uptake of FDG on PET, who was subsequently found to have a lymphoma on biopsy.
Thus, a biopsy should be performed in symptomatic patients to confirm the diagnosis of MP, because imaging specificity is limited since a broad differential diagnosis exists for mass lesions of the mesentery, particularly mesenteric tumour involvement [5
The pathological mechanism of MP is not clearly known but would appear to involve a nonspecific response to a wide variety of stimuli. Daskalogiannaki et al. [5
] reported the co-existence of MP and various neoplastic diseases not involving the mesentery in up to 69% of patients with MP, most commonly urogenital malignancies and digestive carcinoma or lymphoma but also extra-abdominal malignancies such as lung and breast carcinoma. Association of MP and malignancy was previously indicated in the literature [1
] with 30% of patients with MP having an underlying malignancy such as lymphoma, for example in 8/53 patients (4.24%) [22
]. The pathogenic link between MP and malignant disease remained unclear and a possible paraneoplastic response was suggested [5
]. Besides neoplastic disorders, Emory et al. [1
] reported a series of MP in which 4.76% of patients had a history of abdominal trauma or surgery, suggesting an inflammatory post-traumatic fat response [24
]. Furthermore, the disease was also related to other factors such as infectious [25
] and autoimmune diseases [5
], vasculitis [20
], vascular insufficiency, cirrhosis, peptic ulcer, pancreatitis or abdominal aortic aneurysm [5
]. Finally, MP can occur without pre-existing or co-existing disease and can be classified as idiopathic, as was the case in our observation.
MP has been included in the field of fibrotic disorders such as retroperitoneal fibrosis, sclerosing cholangitis, Riedel’s thyroiditis and orbital pseudo tumour [11
]. The pathogenesis of these fibrotic disorders may be related as they share common histological features and may have both elevated serum IgG4 levels and IgG4-producing plasma cell expansion in affected organs with fibrotic or sclerotic changes [26
]. In our case, the patient did not have elevated serum levels of IgG4. IgG4-related disease is a systemic syndrome classically considered as a distinct entity belonging to the differential diagnosis of MP. However, they can sometimes mimic one other. Both diseases rarely co-exist as evidenced by two recent Japanese cases reporting IgG4-related sclerosing mesenteritis [27
]. Moreover, a recent review on the subject proposes adding sclerosing mesenteritis to the list of diseases associated with IgG4 disorders [29
]. Further studies will be required to confirm such an association.
Several therapies have been proposed to treat MP but no consensus has been established since no one therapy has been shown to be superior to the others. Treatment may include steroids [4
], thalidomide, cyclophosphamide [32
], progesterone [33
], colchicine [12
], azathioprine [16
], tamoxifen [4
], antibiotics, or radiotherapy.
The surgical approach should be limited to biopsy of the mass; resection or bypass procedures are proposed only in cases of bowel obstruction or perforation [12
]. Although Adachi et al. [10
] found that MP of the colon seems to be more progressive with surgical treatment required more often than MP of the small intestine, our patient did not require surgery and had spontaneous improvement.
MP is a rare entity that occurs independently or in association with other disorders. This process mainly affects the mesentery of the small intestine but involvement of the colon is not uncommon. Diagnosis is a challenge despite the help of imaging tools, and histological analysis is necessary in some symptomatic cases in order to rule out treatable alternate etiologies. Overall the prognosis is usually good with supportive treatment, even in symptomatic cases like the one reported here.