Occurrence of systemic complications after a large abdominal hernia operation depends on the increase of intraabdominal pressure (IAP). It is thus essential to device a preoperative method to predict IAP level changes in perioperative period.The aim of the study was evaluation of our own mathematical calculation of hernial sac volume in prognosis of intraabdominal pressure changes after abdominal wall reconstruction.Material and methods. Between January 2006 and November 2007 32 patients were operated because of a large abdominal hernia. Secondary hernias made up 68.8%, whereas primary hernias 31.3%. Mean patients' age was 67.5 years. Using our own method of mathematical calculation of hernial sac volume, the patients were divided into groups according to hernia size. Intraabdominal pressure values and their influence on respiratory, circulatory and excretory systems have been analyzed. The operation was conducted under intratracheal anesthesia. The abdominal wall plasty was carried out using a polypropylene mesh that has been placed in the prefascial retromuscular space.Results. No perioperative deaths were observed. The highest mean IAP increase occurred after hernial ring closure, whereas the highest mean abdominal perfusion pressure (APP) drop was observed in the first 24 hours after the operation. There was observed a positive correlation between hernial sac volume (HSV) and IAP values and a negative one between HSV and APP value. There was observed a decrease of diuresis, saturation, blood pressure and an increase of urea and creatinine in the first 24 hours after the operation.Conclusions. A non-invasive hernial sac volume measurement helps to predict postoperative IAP growth and thus development of general complications. Pressure-free operations seem to be safe in terms of preventing post-operative intraabdominal pressure growth.