An adapter is connected to a probe tube of a PEG probe that is already in place, the probe tube being cut off above the abdominal wall of the patient. The adapter comprises an outer retaining element, which is supported on the abdominal wall, and comprises structure for fastening the proximal end of the PEG probe, and structure for connecting a delivery line to the flow channel. A shut-off element having a rotatable or displaceable closing body is provided for closing the PEG probe. The adapter is characterized by its universal use, simple handleability and small overall height.