A method and apparatus for measuring the intra-abdominal pressure (IAP) within a patient having a naso-enteric tube. The system senses the IAP of the patient by means of a sensing conduit that is filled with a sensing fluid. The sensing fluid in the sensing conduit may be saline, water or feeding solution. After the sensing conduit is filled with the sensing fluid, the sensing conduit is elevated and a portion of the sensing fluid enters the patient. The remaining portion of the sensing fluid is related to the IAP and the IAP may be determined from the height of the sensing fluid within the sensing conduit.