We do the first leak test during the operation. At the end of the operation, we inject a blue dye through a tube that we place in the stomach of the patient. We observe whether this blue dye escapes from the seams. If there is a problem, we intervene immediately. On the 1st postoperative day, we perform the leak test by using this blue dye or by taking a tomography or x-ray by containing a contrast liquid to the patient.