It is important to assess the position and orientation of lap bands when viewing radiographs or CT.  The most useful measurement is the phi angle i.e. the angle subtended by the vertical column and band in profile. It should be between 4 and 55 degrees. If it is greater the band has slipped. On x-ray, the band should always be seen in profile. If the band is seen as an ovoid/circle then it has rotated in position. This is always abnormal. If the band moves it can cause obstruction to the proximal stomach and even erose into the lumen. In this case, there is an obstruction to the proximal stomach and probable venous ischemia leading to marked mural edema.