Intra-abdominal hypertension and abdominal compartment syndrome

What it is

The abdomen is a closed space with limited stretch. When its contents swell (oedematous bowel, blood, ascites, packs) or its wall cannot expand (burns eschar, tight closure), intra-abdominal pressure (IAP) rises. Intra-abdominal hypertension (IAH) is a sustained or repeated IAP of 12 mmHg or more, graded I to IV as it rises; abdominal compartment syndrome (ACS) is a sustained IAP above 20 mmHg with new organ dysfunction. Primary ACS comes from disease or injury in the abdomen or pelvis (trauma, haemorrhage, pancreatitis, ruptured aortic aneurysm, surgery); secondary ACS follows conditions outside the abdomen that cause capillary leak and massive fluid resuscitation (sepsis, burns, shock). High pressure lowers venous return and cardiac output, pushes the diaphragm up (high airway pressures, hypoxaemia, hypercapnia), compresses the renal veins and parenchyma (oliguria is often the first sign), reduces gut perfusion and raises intracranial pressure. Physical examination is unreliable, so IAP is measured, usually through the bladder catheter. Abdominal perfusion pressure (mean arterial pressure minus IAP) helps guide treatment. Management first uses medical measures to empty the bowel, remove fluid collections, improve wall compliance and avoid excess fluid; decompressive laparotomy is the definitive treatment when ACS persists.

How to recognise it

• Measure IAP in any patient with risk factors and a new organ failure: massive resuscitation, abdominal surgery or trauma, pancreatitis, burns, ileus, ascites.
• A tense, distended abdomen supports the diagnosis but the examination misses many cases; only measurement confirms it.
• Oliguria despite adequate blood pressure is often the earliest organ sign.
• Rising peak and plateau airway pressures, falling tidal volumes in pressure modes and worsening oxygenation point to diaphragm splinting.
• Low cardiac output with high central venous pressure and a tense abdomen should prompt an IAP measurement, not more fluid.

Why it happens

• Pressure on the inferior vena cava and a raised intrathoracic pressure reduce venous return, preload and cardiac output.
• The diaphragm is pushed up, which lowers chest wall compliance and lung volumes and raises airway pressures.
• Renal vein compression and reduced renal perfusion lower glomerular filtration and cause oliguria.
• Gut ischaemia increases bowel wall oedema, which raises IAP further: a vicious cycle; bacterial translocation may follow.
• Raised intrathoracic pressure impairs cerebral venous drainage and raises intracranial pressure.

What to do at once

1. Measure IAP through the bladder at end-expiration, supine, zeroed at the mid-axillary line — the trend guides every decision.
2. Optimise sedation and analgesia, and consider neuromuscular blockade for a short time — a relaxed abdominal wall lowers pressure.
3. Decompress the gut: nasogastric and rectal tubes, prokinetics, stop enteral feeding if needed — an empty bowel takes less space.
4. Drain ascites or fluid collections percutaneously when imaging shows them — removing volume lowers pressure quickly.
5. Stop the positive fluid balance: restrictive fluids after resuscitation, diuretics or RRT to remove fluid — oedema drives the cycle.
6. Loosen tight dressings and avoid head-up positions above what is needed — both stiffen the abdominal wall.
7. If ACS persists with organ failure, call the surgeon for decompressive laparotomy — delay causes irreversible organ damage.

Grades of intra-abdominal hypertension

Costly mistakes

• Trusting the abdominal examination instead of measuring IAP.
• Reading a high central venous pressure as adequate filling, or giving more fluid for oliguria caused by compression.
• Measuring with the patient sitting up, during abdominal muscle contraction or with a wrongly zeroed transducer, which gives false values.
• Delaying decompression in a patient whose organs keep failing despite medical measures.
• Closing the abdomen tightly after damage-control surgery in a patient with massive bowel oedema.

Next step

• Record IAP at the intervals set by the unit protocol while risk persists, with abdominal perfusion pressure and urine output.
• Call the surgeon and the senior intensivist when IAP keeps rising or a new organ failure appears.
• After decompression, watch for reperfusion hypotension, bleeding and infection; plan staged abdominal closure.
• Monitor kidney function, lactate and ventilation as IAP falls to confirm recovery.

Test yourself

Think of the answer, then tap the question to see it.

Add to my cards (4)

Elsewhere in DurgiPedia

• Acute abdomen and peritoneal irritation
• Abdominal palpation: light and deep, guarding and masses
• Renal blood flow, autoregulation and tubuloglomerular feedback

Connections

← All of anaesthesia

Educational content; it does not replace supervised training, your institution's protocols or the anaesthetist's or intensivist's decision. It contains no doses and no ventilator or infusion settings.

Sources: Abdominal Compartment Syndrome (StatPearls (NCBI Bookshelf), 2025).

Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake

Send

Representative model, for educational purposes only.