Desmoid Tumor Associated With Familial Adenomatous Polyposis: Evaluation With 64-Detector CT Enterography

DTs, also called abdominal fibromatosis are benign tumors which are not seen very often, and most of the radiologists and clinicians do not know the characteristics of them very well (1, 2). The etiology of DT is genetic predisposition (in patients with FAP or Gardner syndrome), trauma, prior abdominal surgery and hormonal factors (endogenous level of estrogen, pregnancy) (4). DTs are generally seen between 20 and 40 years of age as in our case and generally occur after colectomy in patients with FAP or Gardner syndrome (1, 2). DTs are locally aggressive tumors which do not metastasize, but recurrence ratios are high especially in patients with FAP (2). The small bowel mesentery, musculoaponeurotic structures of the anterior or posterior abdominal wall, especially the rectus and oblique muscles and their fascial coverings are the most common sites of origin for DTs (1, 2, 4).

DTs are often asymptomatic, but can represent as abdominal pain, palpable abdominal mass, nausea, anemia, vomiting, diarrhea or fever (1, 2, 8). DT complications are partial or complete obstruction of the small bowel or ureter as a result of intestinal or ureteral compression, intestinal perforation with or without peritonitis, abscess and fistula formation (1, 2, 4, 8). Small bowel ischemia, mucosal ulcerations and/or gastrointestinal bleeding occur as a result of increased compression or invasion of mesenteric vessels (1, 2, 4, 8).

The treatment options for DTs include medical therapy (e.g. non-steroidal anti-inflammatory drugs, antiestrogens), cytotoxic chemotherapy, radiation therapy or surgery (1, 2). Due to a higher recurrence risk and more difficult disease control, non-invasive treatment methods should be planned in the first place for FAP patients with DT different from sporadic cases (1). Surgical treatment option should be kept only for patients in whom complication has occurred (e.g. small bowel obstruction or perforation) (2-5).

The radiologic characteristics of DTs could be changed according to their fibroblastic proliferation, collagen component, vascularity and fibrosis (1, 2, 8). On US, DTs have variable echogenicity and homogeneity with or without smooth, well-defined margins (8). US which is not the first option for mesenteric DT evaluation can be useful for detecting abdominal wall localized DTs. Thus, CT and MRI should be preferred for DT assessment in the first line (1).

On contrast-enhanced abdominal CT scans, most DTs appear as homogeneous masses with well- or ill-defined margins that may have iso- or hyperdense appearance relative to muscle planes (1, 2). Some cases of heterogeneous masses with infiltrative outer margins have been seen (2). DTs may enhance after injection of IV contrast material (1). On MRI, DTs appear as masses with low signal intensity relative to muscle planes on T1 weighted (W) sequences (2). DTs could show various signal characteristics on T2W sequences due to their hysto-pathological features (8). In summary, radiological characteristics of these tumors are directly related to their underlying histopathologic features and vascularity (1). Therefore, there is no significant imaging criterion for DTs. Lymphomas, mesenteric sarcomas and gastrointestinal stromal tumors should be considered in the differential diagnosis of DTs from other mesenteric and abdominal solid lesions. Nonetheless, first of all, DTs should be considered for mesenteric and anterior abdominal wall masses in patients with FAP or Gardner syndrome and cases with surgery or trauma history (2).

CTE is a relatively new technique which is used generally in patients with Crohn’s disease and other small bowel pathologies (9, 10). The difference between CTE and conventional and CT enteroclysis is that; there is no need for nasojejunal intubation and as a result, there is better patient comfort and less radiation exposure (9, 11). Colectomy is the preferred operation for patients with polyposis syndrome as performed in our patient. Providing luminal distension using routine oral contrast agents is almost impossible in such patients due to the short intestinal transit time. The oral contrast agent which was used for CTE examination was developed for small bowel distension. Thus, the optimal luminal distension could be achieved and the relation of DTs with the small bowel and mesenteric structures could be clearly demonstrated.

The advantages of CTE with MDCT are scanning the whole abdomen with thin slices in one breath time, taking multiplanar reformatted images and showing the small bowel and the surrounding tissues directly (12, 13). The disadvantage of CTE and the difference from MR enterography (MRE) is the radiation exposure (9). Thus, MRE can be a new follow up modality in the evaluation of young patients (9, 12). However, MRE has its own limitations and disadvantages, as it cannot be applied for claustrophobic or uncooperative patients and is highly sensitive to movement and post-operative metallic materials (9).

As a result of the developments in CT technology, there has been significant improvement in reformatted image quality. We could evaluate the extension of mesenteric DTs, surrounding the small bowel and the vessels with 64 detector MDCT which could not be detected by US or endoscopy. Besides, we could easily determine the relationship between anterior abdominal wall localized DTs and the small bowel or the intraperitoneal space with CTE. New and comprehensive studies are needed to determine the role of CTE in demonstrating the relation of DTs with the small bowel and mesenteric structures. The effect on the prognosis and also the role of the morphological appearance of DTs in enterographic images on the surgical plan should be assessed in detail in those further studies.

According to the results of our case, CTE is a useful technique for the evaluation of DT location, degree of extension and invasion to local structures, or the presence of partial/complete small bowel obstruction and the relationship of the tumors with vasculature and whether ischemia has occurred as a result or not. CTE is good also for examining extra-intestinal complications such as fistulas, urinary tract obstruction and abscess formation.

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