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KembaraXtra-Medicine: Abdominal Compartment Syndrome
Abdominal compartment syndrome (ACS) is defined as organ dysfunction caused by increased intraabdominal pressure, also referred to as intraabdominal hypertension. When pressure within the abdomen rises, blood flow to vital organs falls, which can rapidly progress to multisystem organ failure and death if not recognized and treated promptly. The ICD-10-CM code is M79.A3 (Nontraumatic compartment syndrome of abdomen).
The true incidence of ACS outside trauma populations is not well defined, but among trauma patients it has been reported in roughly 1% to 14%, depending on the patient population and type of injury. ACS is most commonly seen in critically ill patients, and critical illness itself is the largest overarching risk factor. A particularly important trigger is large-volume intravenous fluid resuscitation, because “third-spacing” and tissue edema can increase intraabdominal pressure. As a result, ACS is often associated with severe burns, major trauma, postoperative states, and sepsis. It is also linked to intraabdominal or retroperitoneal conditions that increase abdominal contents or reduce abdominal wall compliance, including bowel distention/obstruction or ileus, pancreatitis with retroperitoneal edema, massive ascites, hemoperitoneum (such as after ruptured abdominal aortic aneurysm), liver transplantation, and large intraabdominal or retroperitoneal hematomas.
Clinically, the most striking physical finding is typically marked abdominal distention. Patients often develop difficulty with ventilation and decreased urine output, which are common early clues to organ compromise. Additional findings may reflect poor perfusion and shock physiology, including hypotension, cool extremities, skin mottling, and altered mental status. Many patients have abdominal tenderness and signs of volume overload such as edema and elevated jugular venous pressure, and they may deteriorate quickly with acute respiratory decompensation.
ACS can impair nearly every organ system because elevated intraabdominal pressure disrupts both perfusion and mechanics. Rising abdominal pressure can increase intracranial pressure, potentially worsening cerebral perfusion. Cardiovascular compromise can occur through reduced venous return from inferior vena cava compression and reduced ventricular compliance, leading to higher central venous and pulmonary pressures and reduced cardiac output. Respiratory failure is common because elevated abdominal pressure pushes the diaphragm upward, reducing chest wall compliance and tidal volumes, which contributes to atelectasis, hypoxemia, hypercarbia, and pneumonia. Mechanically ventilated patients may require higher airway pressures, increasing the risk of barotrauma. Renal dysfunction occurs as renal vein compression and renal arterial vasoconstriction reduce renal blood flow, producing oliguria or anuria. Reduced mesenteric perfusion may cause bowel ischemia and lactic acidosis.
A definitive diagnosis requires direct measurement of intraabdominal pressure, most commonly estimated using bladder pressure measured through a urinary catheter. For accuracy, measurements are ideally obtained with the patient supine, at end-expiration, and without active abdominal muscle contractions. While many research definitions use a threshold of >20 mm Hg with associated organ dysfunction, ACS may occur at lower pressures in susceptible patients. Oliguria commonly appears around 15 mm Hg, and anuria may occur near 30 mm Hg. Other measurement approaches (such as intragastric or intracolonic pressure estimation) exist but are used less commonly. Laboratory studies are generally not diagnostic, although lactic acidosis can suggest bowel ischemia and signals a worse prognosis. Imaging does not establish ACS, but chest imaging may show diaphragmatic elevation or pulmonary complications, and abdominal CT may sometimes demonstrate findings such as vena cava compression or bowel ischemia-related injury—these should be considered supportive rather than diagnostic.
Treatment focuses on supportive care and rapid reduction of intraabdominal pressure, with surgical decompression as the only definitive therapy when conservative measures fail or when pressures and organ dysfunction are severe. Supportive management includes aggressive hemodynamic and ventilatory support, along with measures to improve abdominal wall compliance. Patients should be kept supine when possible, since head-of-bed elevation can raise intraabdominal pressure. Nasogastric and rectal decompression may be required when bowel distention is contributing. Adequate sedation and analgesia help reduce abdominal wall muscle tone, and some patients need chemical paralysis to maximize relaxation. If tense ascites is a major contributor, large-volume paracentesis can substantially lower pressures. In patients with severe abdominal burns, escharotomy may be necessary to restore abdominal wall compliance. Mechanical ventilation is often challenging and may require low tidal volumes, permissive hypercapnia, high PEEP, and paralytics to maintain adequate gas exchange.
Although vasopressors, fluids, sedatives, analgesics, and paralytics are used to stabilize the patient, there are no medications that directly treat ACS, and diuretics do not play a therapeutic role even when patients appear volume overloaded. If intraabdominal pressure remains high with ongoing organ dysfunction, surgical decompression is performed, typically by opening the abdomen via a midline incision through the linea alba. In emergent situations this can be done at the bedside, followed by temporary abdominal closure (often vacuum-assisted systems) to prevent evisceration, manage fluid loss, and allow delayed closure once swelling resolves. Many consensus recommendations support decompression when pressures exceed 25 mm Hg, though some clinicians will intervene earlier in the right clinical context, recognizing that earlier decompression may improve outcomes.
Because mortality with ACS can be very high, often greater than 40%, patients require close inpatient monitoring—preferably in an intensive care unit—and early surgical consultation. The key clinical principle is that ACS is both a pressure problem and an organ failure syndrome: diagnosis requires evidence of intraabdominal hypertension plus end-organ dysfunction, and definitive management depends on timely decompression when supportive measures are insufficient.
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