How to recognize an acute abdomen and identify when an urgent surgical referral is required

Severe, acute abdominal pain with an abrupt onset of less than 24 hours is known as an acute abdomen. This is often associated with fever, tachycardia, hypotension, or hypoxia. The initial assessment should be quick and accurate to determine if immediate surgical intervention is needed.

Peritonitis is extremely painful, and during an abdominal exam the patient may present with one or all of these three acute abdomen signs:

1. Rigid abdomen
2. Guarding of the abdomen
3. Rebound tenderness

The pain felt in an acute abdomen is caused by peritonitis (e.g., inflammation of the peritoneum). Peritonitis can be caused by conditions such as a perforated peptic ulcer, small or large bowel obstruction or perforation, diverticular disease, or inflammatory bowel disease (IBD).

Rigid abdomen

A rigid abdomen involves involuntary stiffness of the abdominal wall muscles. The patient cannot forcibly relax the muscles.

Guarding of the abdomen

Guarding is the voluntary or involuntary tensing of the abdominal muscles, and tends to be generalized over the entire abdomen.

Voluntary guarding is a conscious contraction of the abdominal wall in anticipation of an exam that will cause pain. Involuntary guarding is a reflex contraction or spasm of the abdominal muscles on palpation due to localized peritoneal inflammation. With involuntary guarding, the muscles often remain in spasm throughout the respiratory cycle. It is similar to rigidity except that it is associated with palpation, while rigidity is not.

To differentiate between voluntary and involuntary guarding, pay attention to the patient’s nonverbal clues during a conversation while palpating the abdomen. With voluntary guarding, the patient will consciously contract the abdominal muscles in anticipation of the physician laying hands on their abdomen.

Rebound tenderness

The third symptom of an acute abdomen is rebound tenderness, which is also known as a Blumberg’s sign. Rebound tenderness involves tenderness with the sudden withdrawal of manual pressure. This causes more pain than the actual application of pressure during an abdominal exam.

To assess for rebound tenderness, deeply palpate a section of the abdomen and hold it down for 5 seconds, then rapidly release the pressure. Ask the patient if pressing down or releasing caused more pain. If the patient experienced more pain when you released the pressure, then the patient is experiencing rebound tenderness.

Conditions involving major blood loss

Some acute abdominal conditions, such as bleeding, require an urgent surgical consultation. There are five sources of massive blood loss that require an urgent referral:

1. Ruptured abdominal aortic aneurysm (AAA)
2. Gastrointestinal bleed
3. Bleeding peptic ulcer
4. Trauma
5. Bleeding diverticular disease

These conditions may require more than 4–6 units of packed red blood cells within 24 hours. Large blood loss is often associated with hemodynamic instability; patients often present with hypotension and tachycardia. During the exam, the patient will also appear pale, cool, and clammy.

Perforated viscus

Another urgent condition is a perforated viscus such as a bowel perforation. In this condition bowel contents leak into the abdomen, which is extremely irritating to the peritoneal cavity. These patients present with tachycardia, hypotension, and fever.

Ischemic bowel disease

Ischemic bowel disease is also an urgent condition. These patients tend to have abdominal pain out of proportion to what is found on the exam. The pain is diffuse and constant, and the patient may present with hypotension or hypertension, a rigid abdomen, and tachycardia.

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