The present invention relates to an apparatus for determining the peritoneal pressure in the abdomen of a patient and/or for determining the drainage state of the abdomen of a patient, wherein the apparatus comprises at least one pump for conveying a dialysis solution into the abdomen as well as at least one measurement device for measuring the pressure in the dialysis solution, wherein the apparatus comprises at least one control unit that is configured such that it controls the pump and the measurement device such that a first measurement of the pressure is carried out by the measurement device with a stationary pump to obtain a first measured pressure value, the pump is subsequently put into operation to convey a partial volume of the total inflow volume of the dialysis solution into the abdomen, and the pump then stops, and then a second measurement of the pressure is carried out by the measurement device to obtain a second measured pressure value.
