Correct monitoring of medicosurgical critically-ill patients aids the early diagnosis and appropriate treatment of intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS). The abdominal cavity and the retroperitoneum act sealed compartments and any change in the volume of their contents can increase intraabdominal pressure (IAP). IAH is only one measure of elevated IAP, and ACS represents the end result of sustained IAH with the appearance of organ dysfunction. To diagnose IAH and ACS, measurement of IAP, abdominal perfusion pressure and intramucous gastric pH must be performed and the results correlated with signs of clinical deterioration in the patient. Medical therapeutic measures in ACS are limited and abdominal decompression is the established symptomatic treatment of this entity.