What is the workup for abdominal compartment syndrome (ACS)?

Workup for Abdominal Compartment Syndrome

Measure intra-abdominal pressure (IAP) via trans-bladder technique whenever any risk factor for intra-abdominal hypertension or ACS is present in a critically ill patient, and diagnose ACS when IAP exceeds 20 mmHg with new organ dysfunction. 1

Diagnostic Criteria

ACS is definitively diagnosed when:

• IAP >20 mmHg (sustained) 1, 2
• New organ dysfunction/failure is present 1, 2

The diagnosis requires both criteria to be met simultaneously. 3

IAP Measurement Technique

Use the trans-bladder (intravesical) measurement technique as the standard method for IAP assessment, as it is simple, low-cost, and recommended by the World Society of the Abdominal Compartment Syndrome. 1

Measurement Protocol:

• Measure IAP at least every 4-6 hours in critically ill patients with risk factors for IAH/ACS 1, 4
• Use protocolized monitoring and management rather than ad hoc measurements 1
• Sustained bladder pressures beyond 20 mmHg with organ dysfunction are diagnostic 3

Clinical Assessment of Organ Dysfunction

Evaluate for multi-system organ failure across the following domains:

Respiratory Effects:

• Hypoventilation from restricted diaphragmatic deflection 3
• Reduced chest wall compliance 3
• Hypoxemia and V/Q mismatch 3

Cardiovascular Effects:

• Decreased venous return 3
• Reduced cardiac output 3
• Compromised tissue perfusion 3

Renal Effects:

• Decreased urine output (prerenal from vascular compression or intrarenal from glomerular compression) 3
• Renal impairment 5

Gastrointestinal Effects:

• Compromised perfusion to intra-abdominal organs 3

Neurologic Effects:

• Consider elevated intracranial pressure in patients with brain injury, as IAP affects ICP 4

Imaging Studies

CT scanning plays a crucial role in detecting and characterizing pathological conditions that may lead to IAH/ACS, particularly when intravesical pressure measurement is not immediately available. 5

CT findings to evaluate:

• Increased intra-abdominal volume (ileus, ascites, trauma, pancreatitis) 5
• Decreased abdominal wall compliance 5
• Underlying pathology causing pressure elevation 5

Risk Factor Assessment

Identify patients at risk by screening for:

Primary Risk Factors:

• Abdominal trauma requiring damage control surgery 1
• Injuries requiring packing and planned reoperation 1
• Severe acute pancreatitis (approximately 15% develop IAH/ACS) 6
• Ruptured abdominal aortic aneurysm 1
• Acute mesenteric ischemia 1
• Severe intra-abdominal sepsis 1

Secondary Risk Factors:

• Aggressive fluid resuscitation and massive transfusion 3, 2
• Extreme visceral or retroperitoneal swelling 1
• Obesity 1
• Abdominal wall tissue loss 1
• Persistent hypotension, acidosis (pH <7.2), hypothermia (<34°C), and coagulopathy 1

Abdominal Perfusion Pressure

Consider calculating abdominal perfusion pressure (APP = MAP - IAP) as an additional resuscitation endpoint, analogous to cerebral perfusion pressure, though formal recommendations for its routine use are lacking. 1, 2, 4

Monitoring Frequency

Once IAH is detected (IAP ≥12 mmHg):

• Continue serial IAP measurements every 4-6 hours or continuously 1
• Titrate therapy to maintain IAP <15 mmHg 1, 4
• Escalate to more frequent monitoring if IAP approaches 20 mmHg 1

Common Pitfalls

Do not wait for all organ systems to fail before measuring IAP—early detection in at-risk patients is paramount given the 50% mortality rate even after treatment. 2, 6

Do not rely solely on clinical examination to diagnose ACS, as the clinical presentation is varied and can mimic other pathologies. 7

Recognize that abdominal compliance plays a key role—once maximum distension is reached, IAP becomes highly sensitive to any additional volume. 3