Neuro-endocrine tumours (NET) are the most frequent tumours of the small intestine. In spite of their small size, these tumours have the particularity of forming mesenteric metastasis and ganglionic secondary lesions along the superior mesenteric axis, which is in close proximity to the superior mesenteric artery (SMA).

Surgery is the only curative treatment. The complete resection being a factor for good patient prognosis, risks of subsequent local complications (occlusion, bleeding) must be discussed. The limiting factor for resectability is arterial vascular invasion considering the risk of postoperative small bowel syndrome.

At the moment, the choice of imaging examination and its protocol is not standardized, nor the description of the tumoral mesenteric and ganglionic extension, especially the criteria defining a lymph node as lymphadenopathy. In addition, the complexity of SMA's anatomy and the absence of criteria for arterial invasion defining arterial invasion may lead to a misinterpretation of the preoperative imaging , and thus to an incomplete planning of the surgical procedure.

To correct this absence of radiological standardization, the investigating team has developed a reading grid for Computed Tomography (CT) aimed to facilitate preoperative planning of small bowel NET.

The main objective of the current study is to improve the semiotic description of the mesenteric and ganglionic tumoral extension of small intestine NET using a technically optimized imaging examination and a standardized reading grid in order to plan the best surgical procedure which would allow maintaining a minimal length of small intestine needed to yield a satisfying quality of life and nutritional status.

The secondary objective of this study is to evaluate the reproducibility of the standardized scanner's reading grid.

Inclusion Criteria:

• Patients with small intestine neuro-endocrine tumors (NET) operated in the digestive surgical service of the University Edouard Herriot hospital of Lyon (Pr. Gilles Poncet) between the 1st of January 2014 and the 31st of March 2019,
• Having done a preoperative thoraco-abdomino-pelvic scanner with arterial and portal sequences.
• Scanner imaging, operative report and anatomo-pathological report available

Exclusion Criteria:

• no Computerized Tomography (CT) images available

Male and female patients at least 18 years old with small intestine neuro-endocrine tumors (NET)