Abdominal compartment syndrome (ACS) manifests with increase of intra abdominal pressure (IAP) and organ dysfunction resulting in multiple organ failure. ACS presents with respiratory failure, hemodynamic changes, and impaired renal function. ACS is most often observed in critically ill patients with peritonitis, gastric dilatation, intestinal obstruction intra abdominal abscesses, abdominal trauma, and sepsis. In the absence of complex treatment mortality can reach 100%.Examine the IAP changes in the postoperative period in ICU patients with complicated abdominal surgery.Ten patients after abdominal surgery on mechanical ventilation were examined. From the existing methods for measurement of IAP we chose to determine the pressure in the bladder.We observed IAP changes, hemodynamic instability, oliguria, and acid base balance impairment. In two patients IAP reached levels above 25 mmHg while the increase in the other eight patients was moderate between 8 and 17 mmHg. Two of the patients had an anastomotic leak which necessitated relaparotomy.IAP level above 25 mmHg is associated with impairment of the blood flow in the major abdominal vessels which can lead to respiratory, cardio circulatory, liver, and renal failure. Currently the surgical decompression is the only treatment leading to significant mortality reduction.