What is abdominal compartment syndrome?

Abdominal Compartment Syndrome Definition

Abdominal compartment syndrome (ACS) is defined as a sustained intra-abdominal pressure (IAP) ≥ 20 mmHg (with or without an abdominal perfusion pressure < 60 mmHg) that is associated with new organ dysfunction or failure. 1

Core Diagnostic Criteria

The World Society of the Abdominal Compartment Syndrome established the following essential parameters for ACS:

• Pressure threshold: Sustained IAP ≥ 20 mmHg 1
• Clinical manifestation: New organ dysfunction/failure must be present and attributable to the elevated IAP 1
• Optional criterion: Abdominal perfusion pressure (APP) < 60 mmHg may be present but is not required for diagnosis 1

Measurement Standards

IAP measurement must follow specific technical requirements to ensure diagnostic accuracy:

• Reference standard: Intravesical (bladder) measurement using a maximal instillation volume of 25 mL sterile saline 1
• Measurement technique: Expressed in mmHg, measured at end-expiration in the supine position with abdominal muscle contractions absent 1
• Transducer position: Zeroed at the level of the midaxillary line 1

Clinical Context

Normal IAP in critically ill adults is approximately 5-7 mmHg, making the ACS threshold of ≥20 mmHg a substantial pathologic elevation. 1

Classification by Etiology

ACS is categorized based on the anatomic origin of the pathology:

• Primary ACS: Associated with injury or disease in the abdominopelvic region, frequently requiring early surgical or interventional radiological intervention 1
• Secondary ACS: Conditions that do not originate from the abdominopelvic region (e.g., massive fluid resuscitation, capillary leak, sepsis) 1
• Recurrent ACS: IAH or ACS that redevelops following previous surgical or medical treatment 1

Relationship to Intra-Abdominal Hypertension

ACS represents the severe end of the intra-abdominal hypertension spectrum. Intra-abdominal hypertension (IAH) is defined as sustained or repeated pathological elevation in IAP ≥ 12 mmHg, and is graded as follows: 1

• Grade I: IAP 12-15 mmHg
• Grade II: IAP 16-20 mmHg
• Grade III: IAP 21-25 mmHg
• Grade IV: IAP > 25 mmHg

ACS develops when IAH progresses beyond the pressure threshold of 20 mmHg and causes organ dysfunction. 2, 3

Organ System Effects

The organ dysfunction defining ACS can affect multiple systems:

• Cardiovascular: Decreased cardiac output from compression of the inferior vena cava and increased intrathoracic pressure 4, 3
• Respiratory: Impaired ventilation from diaphragmatic elevation and decreased chest wall compliance 4
• Renal: Acute kidney injury from decreased renal perfusion pressure and direct parenchymal compression 3
• Gastrointestinal: Reduced splanchnic perfusion and intestinal ischemia 4
• Central nervous system: Increased intracranial pressure from impaired venous return 4

Pediatric Considerations

In children, ACS is defined as a sustained elevation in IAP greater than 10 mmHg associated with new or worsening organ dysfunction attributable to elevated IAP. 1 The lower threshold reflects physiologic differences in pediatric patients, with normal IAP in critically ill children approximately 4-10 mmHg. 1

Clinical Significance

ACS is associated with high morbidity and mortality if diagnosis is delayed, making early recognition critical. 2, 3, 5 The condition is most commonly observed in severe abdominal trauma, but occurs across diverse clinical scenarios including acute pancreatitis, massive fluid resuscitation, sepsis, and major burns. 1, 2, 4