Intra-abdominal hypertension refers to high pressure within the abdominal cavity. It can reduce the blood supply and oxygen to the area, which may lead to abdominal compartment syndrome (ACS), a condition that causes multiple organ dysfunction.

Both conditions commonly occur in people who are seriously ill. Of those in intensive care units (ICUs), 35% of those who use a ventilator have one or the other.

Once the pressure is high enough to cause ACS, symptoms may include wheezing, a tense abdomen, and trouble breathing.

Early nonsurgical treatment may prevent the high pressure from resulting in ACS. However, when this is not effective, the main treatment is a surgical procedure called a decompressive laparotomy.

This article discusses intra-abdominal hypertension, including the causes, symptoms, and how it may progress to ACS. It also examines the risk factors of both conditions, as well as their diagnosis, treatment, complications, and outlook.

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Intra-abdominal hypertension (IAH) refers to sustained pressure within the abdomen of 12 millimeters of mercury (mm Hg) or higher. The severity can range from a condition that causes no symptoms to a life threatening condition. It is highly prevalent in people who are in ICUs.

The different grades of intra-abdominal hypertension are as follows:

  • Grade I: Intra-abdominal pressure (IAP) is 12–15 mm Hg.
  • Grade II: IAP is 16–20 mm Hg.
  • Grade III: IAP is 21–25 mm Hg.
  • Grade IV: IAP is greater than 25 mm Hg.

Why is intra-abdominal pressure important?

IAH reduces the blood supply containing oxygen to an array of organs. A lack of oxygen can cause organ dysfunction. The more prolonged the higher pressure in the abdomen, the more harm can occur in the organs, resulting in ACS.

ACS is a life threatening condition. Doctors define it as an elevation of pressure within the abdomen above 20 mm Hg with accompanying organ dysfunction.

When IAH progresses, it can lead to ACS. The causes are likely the same.

Primary causes include:

  • abdominal trauma
  • bleeding
  • intestinal obstruction
  • abdominal aortic aneurysm rupture, which is the bursting of an enlarged area in the main artery in the abdomen
  • peritoneal hematoma, which is a pool of mostly clotted blood that forms in the tissue lining the abdominal wall and pelvic cavity

Secondary causes include:

  • burns
  • intra-abdominal sepsis, an extreme response to an infection within the abdomen
  • ileus, a temporary deficit in normal intestinal movements
  • pregnancy
  • ascites, the accumulation of fluid in the abdomen
  • large-volume fluid replacement

Chronic, or long-term, causes include:

  • obesity
  • cirrhosis, a chronic liver condition involving fibrous thickening of tissue
  • cancer within the abdominal cavity
  • peritoneal dialysis, which is a treatment for kidney failure that uses the abdominal lining to filter blood

A 2020 research article states that often, the condition may not involve symptoms if it is mild.

An older 2011 study reports that more severe intra-abdominal hypertension links to a higher incidence of gastrointestinal symptoms, such as:

When IAH is severe enough to cause ACS, symptoms may include:

  • a tense abdomen
  • wheezing
  • increased abdominal girth
  • cyanosis, a bluish or grayish discoloration of the skin
  • difficulty breathing

Research states that many risk factors can play a role. These include those related to increased intra-abdominal volume, decreased abdominal compliance, or both. Abdominal compliance refers to the elasticity of the abdominal wall and diaphragm, the muscle below the rib cage involved in breathing.

Examples of conditions that may increase intra-abdominal volume include:

Examples of conditions that may decrease abdominal compliance include:

  • obesity
  • tight sutures
  • capillary leaks from trauma, which is bleeding from tiny blood vessels

A diagnosis starts with a physical exam, when a doctor may note symptoms, such as a tense abdomen and trouble breathing. Imaging — such as CT scans — can help determine the cause, such as trauma or an obstruction.

The most accurate method of confirming a diagnosis comes from measuring intra-abdominal pressure.

The early use of nonsurgical treatments can help prevent IAH from progressing to ACS. Options may include muscle relaxation or drainage of abdominal fluid.

A type of surgery, called a decompressive laparotomy, is the ultimate ACS treatment, as it removes the pressure. However, because this involves adverse effects, doctors may reserve it for people who did not obtain good results from nonsurgical interventions. That said, if a person needs urgent treatment, it is vital not to delay the surgery.

Some complications that can occur include:

  • kidney failure
  • difficulty breathing
  • low heart output and shock
  • higher cranial pressure, which is elevated pressure within the skull
  • reduced blood flow to the intestines

If a person does not receive treatment, ACS can be fatal. Delayed treatment also links to very high death rates. Even if someone receives treatment, the failure of multiple organs may necessitate a lengthy hospital recovery period lasting weeks or months.

Intra-abdominal hypertension is a pressure of 12 mg Hg or higher within the abdomen. Increased pressure in the abdominal cavity can have serious consequences. It can reduce the blood and oxygen supply to multiple organs, resulting in abdominal compartment syndrome.

The condition has an array of causes that may include cirrhosis, obesity, or cancer. If it is mild, it may result in no symptoms, but once it progresses to ACS, symptoms may include a tense abdomen, cyanosis, and trouble breathing.

A physical exam may lead a doctor to suspect ACS, and an abdominal pressure measurement can confirm the diagnosis. The ultimate treatment is decompressive laparotomy once the higher pressure results in ACS.

ACS can lead to complications, such as kidney failure and low heart output. Without treatment, ACS is fatal.