# Abdominal Compartment Syndrome > Abdominal compartment syndrome for NEET-PG Surgery: intra-abdominal hypertension grades, bladder pressure measurement, organ effects, and decompression. - Canonical URL: https://prepelephant.com/topics/neet-pg/surgery/abdominal-compartment-syndrome - Exam / course: NEET-PG · Subject: Surgery - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Abdominal Compartment Syndrome", PrepElephant, https://prepelephant.com/topics/neet-pg/surgery/abdominal-compartment-syndrome ## Direct answer Intra-abdominal pressure above 20 mmHg with new organ dysfunction defines abdominal compartment syndrome (ACS); pressures sustained above 12 mmHg define intra-abdominal hypertension (IAH), graded I to IV (12–15, 16–20, 21–25, over 25). Bedside measurement through the urinary catheter — instilling about 25 mL of saline into the bladder and reading end-expiratory pressure — makes this a diagnosis any surgical ward can make, and it must be actively sought in the high-risk: damage-control laparotomy patients, massive resuscitation, burns, pancreatitis and sepsis. Organ effects arrive in a predictable order — reduced urine output and falling cardiac output before the airway pressures climb — and decompressive laparotomy with an open abdomen is the definitive treatment, reinforced by medical measures (neuromuscular blockade, nasogastric and rectal decompression, fluid discipline) at lower grades. ## What you must remember - Normal intra-abdominal pressure is roughly 5–7 mmHg in the resting adult; the World Society of the Abdominal Compartment Syndrome (WSACS) definitions are the reference standard. - Grading of IAH: Grade I 12–15 mmHg, Grade II 16–20, Grade III 21–25, Grade IV above 25; ACS is IAH above 20 mmHg with new organ failure (a clinical state, not a number alone). - Bladder technique: 25 mL saline instilled with the patient supine, transducer zeroed at the iliac crest, read at end-expiration in mmHg — the bladder acts as a passive conduit when the detrusor is relaxed. - Organ effects: oliguria (renal venous compression and reduced cardiac output) is early and proportionate; then reduced venous return and raised airway pressures — the combination of oliguria, high airway pressures and a tensely distended abdomen after resuscitation is the classical triad. - Abdominal perfusion pressure = mean arterial pressure minus intra-abdominal pressure; resuscitation targets an APP of at least 50–60 mmHg, sometimes achievable without surgery. - Risk factors: massive fluid resuscitation (the classic "secondary" ACS after burns or trauma with a normal abdomen initially), damage-control closure under tension, pancreatitis, ileus, peritonitis, liver transplantation, obesity, and high-insufflation laparoscopy. - Management ladder: medical first — sedation and neuromuscular blockade, nasogastric and rectal tubes, positioning, diuretics or renal replacement for fluid overload; then percutaneous catheter drainage of collections; decompressive laparotomy for established ACS, leaving the abdomen open under a temporary closure. - Prophylaxis after damage-control surgery: avoid forced fascial closure under tension; a planned open abdomen with negative-pressure therapy reduces ACS and fistula risk. ## How to work through it Twelve hours after damage-control packing for a liver injury, a ventilated patient who received 14 units of blood and 8 litres of crystalloid becomes oliguric, peak airway pressures climb, and blood pressure requires escalating noradrenaline — while the abdomen is tense and the temporary closure taut. The team measures bladder pressure: 26 mmHg end-expiratory. Cross-check the physiology: abdominal perfusion pressure of 50 mmHg barely clears the threshold; the chest radiograph shows elevated hemidiaphragms. This is Grade IV IAH with organ failure — ACS. Immediate steps: paralysis in the already sedated patient, gastric and rectal decompression, and a low threshold for returning to theatre, because the definitive move is reopening the temporary closure, evacuating packs and oedema, and leaving the abdomen open with a negative-pressure dressing. In the ICU afterwards, the game is prevention of recurrence: fluid restriction or removal, enteral nutrition held to tolerance, and surveillance bladder pressures until closure. The counter-scenario is "secondary" ACS in a burnt child with a soft abdomen at admission: two days of massive resuscitation, then oliguria and rising airway pressures with a newly tense abdomen — the lesson being that ACS appears in patients whose abdomens were never opened, which is why high-risk groups need scheduled pressure measurement rather than a watched-for tense abdomen. ## Where students slip Two measurement slips recur: quoting pressures in centimetres of water (mixing units — the definitions are in mmHg) and describing a bladder measurement with a large instillation volume or during diuresis, both of which distort the reading. Clinically, the favourite error is waiting for the "classical tense abdomen" in a sedated, ventilated patient — in the ICU the presentation is physiological: oliguria plus rising airway pressures plus falling cardiac output. The second error is conceptual — confusing ACS (pressure plus new organ dysfunction) with mere IAH (pressure alone). Third, decompression timing: writing "decompress when convenient" loses the mark — established ACS is a surgical emergency in which hours of delay are irreversible renal and gut ischaemia. ## Frequently asked questions ### How is intra-abdominal pressure measured at the bedside? Through a urinary catheter: instil about 25 mL saline into the bladder, zero the transducer at the iliac crest, and read end-expiratory pressure in mmHg — the validated indirect method. ### What distinguishes intra-abdominal hypertension from abdominal compartment syndrome? IAH is a sustained pressure above 12 mmHg (graded I–IV); ACS is pressure above 20 mmHg with new organ dysfunction — oliguria, respiratory compromise or circulatory failure — making it a clinical syndrome, not a number. ### Which patients need routine pressure monitoring? Damage-control laparotomy patients, massive resuscitation for trauma or burns, severe pancreatitis, sepsis with ileus, and those with closed abdomens under tension after emergency surgery. ### What is abdominal perfusion pressure and its target? Mean arterial pressure minus intra-abdominal pressure; a target of at least 50–60 mmHg guides resuscitation and vasopressor use before resorting to decompression. ### Why does urine output fall early in ACS? Because raised pressure compresses renal veins and parenchyma and reduces cardiac output by impeding venous return — oliguria is the first sign and reverses promptly after decompression.