Gastric Volumetry by Gastric Tomodensitometry With Gas (VOLUSCAN)

The Gastric bypass (GBP) is actually one of the most performed bariatric procedures worldwide. Short term results report 67% of mean Excess Weight Loss (EWL) at 2 years, and 58% EWL at 5 years. Sleeve gastrectomy (SG) which is a restrictive procedure has gained in popularity because of its technical simplicity and its efficiency (60% EWL at 1 year and 48% over 4 years). However, failures are observed because of insufficient weight loss or early weight regain. Several hypotheses have been proposed to explain these failures, such as the size of the gastric pouch that could be correlated to weight evolution. Purpose of the study: Taking the hypothesis that a progressive dilatation of the gastric pouch is one of the main factors of weight loss failure after GBP or SG due to the loss of its restrictive function, the aim of our study is to measure these gastric volumes using gastric tomodensitometry with gas, a new reliable,precise and 3 dimension radiological technique. The investigators will try to identify a positive correlation between gastric dilatation and weight regain.