Pneumoperitoneum

Pneumoperitoneum
hemidiaphragm (on the left of the image) is a pneumoperitoneum.
Specialty	Gastroenterology

Pneumoperitoneum is

• Perforated
  duodenal ulcer
  – The most common cause of rupture in the abdomen. Especially of the anterior aspect of the first part of the duodenum.
• Perforated
  peptic ulcer^[1]
• Bowel obstruction^[2][3]
• Ruptured diverticulum^[4]
• Penetrating trauma^[5]
• Ruptured inflammatory bowel disease (e.g., megacolon)^[6]
• Necrotising enterocolitis/pneumatosis coli^[7]
• Bowel cancer^[8]
• Ischemic bowel^[9][10][11]
• Steroids
• After laparotomy
• After laparoscopy
• Breakdown of a surgical anastomosis
• Bowel injury after endoscopy
• Peritoneal dialysis (PD), although the prevalence of pneumoperitoneum is estimated to be less than 4% among people with PD in a more recent study in the United Kingdom.^[12]
• Vaginal insufflation (air enters via the
  fallopian tubes; e.g., water-skiing,^[13] oral sex^[14][15]
  )
• Colonic or peritoneal infection
• From chest (e.g., bronchopleural fistula)
• Non-invasive PAP (positive airway pressure) can force air down duodenum as well as down trachea.

Spontaneous pneumoperitoneum

A spontaneous pneumoperitoneum is a rare case that is not caused by an abdominal organ rupture. This is also called an idiopathic spontaneous pneumoperitoneum when the cause is not known.

When present, pneumoperitoneum can often be seen on projectional radiography, but small amounts are often missed, and CT scan is nowadays regarded as a criterion standard in the assessment of a pneumoperitoneum.^[18] CT can visualize quantities as small as 5 cm³ of air or gas.

Signs that can be seen on projectional radiography are shown below:

The double wall sign marks the presence of air on both sides of the

The Cupola sign is seen when air is accumulated under the central tendon of the diaphragm.[23]

• 
  Another pneumoperitoneum on chest X-ray.
• 
  Pneumoperitoneum seen on X-ray with the patient lying on his left side.
• 
  Double wall sign. This is a secondary sign of pneumoperitoneum. Patient is supine, and air within the abdomen and lumen of the bowel accentuate both sides of the bowel wall.
• Ultrasound finding of pneumoperitoneum known as "peritoneal stripe sign"^[24]

Differential diagnosis

As differential diagnoses, a subphrenic abscess, bowel interposed between diaphragm and liver (Chilaiditi syndrome), and linear atelectasis at the base of the lungs can simulate free air under the diaphragm on a chest X-ray.^{[citation needed]}

Treatment

Treatment depends on the cause of the condition.^{[citation needed]}

Terminology

Pneumoperitoneum can be described as peritoneal emphysema,^[25] just as pneumomediastinum can be called mediastinal emphysema, but pneumoperitoneum is the usual name.

See also

• Cupola sign
• Football sign
• Pneumoretroperitoneum
• Rigler's sign

References