Pneumoperitoneum

Pneumoperitoneum
Other names: Aeroperitoneum[1]
Chest X-ray with air between the right diaphragm and the liver (green and red arrows). Air also visible below the diaphragm on the persons left. Blue arrows mark a normal gas filled colon.
Specialty	General surgery
Symptoms	None to peritonitis[2]
Complications	Abdominal compartment syndrome[3]
Causes	Gastrointestinal tract perforation, abdominal surgery, peritoneal dialysis, pneumothorax, pneumomediastinum, mechanical ventilation, entry via the vagina[1][4]
Diagnostic method	X-ray, CT scan[2]
Differential diagnosis	Chilaiditi syndrome, pneumomediastinum, atelectasis of the lower lung, bowel wall gas[5]
Treatment	Based on cause, often surgery[6][4]

Pneumoperitoneum is the presence of air or other gas in the peritoneal cavity.^[1] Symptoms may vary from none to peritonitis.^[2] Other symptoms may include abdominal swelling or shortness of breath.^[2] Complications may rarely include abdominal compartment syndrome.^[3]

The most common cause (>90%) is a hole in the gastrointestinal tract.^[1][4] This may occur due to a peptic ulcer, bowel obstruction, appendicitis, or abdominal trauma.^[1] Other causes may include following abdominal surgery, including laparoscopic surgery; peritoneal dialysis, pneumothorax, pneumomediastinum, mechanical ventilation, and entry via the vagina.^[1] Rarely cases may occur due to an unknown cause.^[4] Diagnosis is generally via X-ray or CT scan.^[2]

Treatment depends on the source of the air.^[6] In most cases surgery is required; though certain cases may be managed conservatively.^[4][7] Conservative management may include bowel rest, intravenous antibiotics, and closely watching for worsening.^[2] Cases were detected via X-ray as early as 1915.^[4]

Signs and symptoms

The presentation often involves:^[8]

• Nausea
• Abdominal pain
• Chest pain

Causes

• 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^[9]
• Bowel obstruction^[10][11]
• Ruptured diverticulum^[12]
• Penetrating trauma^[13]
• Ruptured inflammatory bowel disease (e.g., megacolon)^[14]
• Necrotising enterocolitis/pneumatosis coli^[15]
• Bowel cancer^[16]
• Ischemic bowel^[17][18][19]
• 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.^[20]
• Vaginal insufflation (air enters via the fallopian tubes; e.g., water-skiing,^[21] oral sex^[22][23])
• 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.

Diagnosis

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.^[26] 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 intestine.^[27] However, a false double wall sign can result from two loops of bowel being in contact with one another.^[28] The sign is named after Leo George Rigler.^[29] It is not the same as Rigler's triad.

The football sign is when the abdomen appears as a large oval radiolucency reminiscent of an American football on a supine projectional radiograph.^[30] The football sign is most frequently seen in infants with spontaneous or iatrogenic gastric perforation causing pneumoperitoneum. It is also seen in bowel obstruction with secondary perforation, as in Hirschprung disease, midgut volvulus, meconium ileus and intestinal atresia. Iatrogenic causes like endoscopic perforation may also give football sign.

The Cupola sign is seen when air is accumulated under the central tendon of the diaphragm.^[31]

• 
  a) X-ray of abdomen, showing subdiaphragmatic free air, air outlining the properitoneal fat stripe black arrows b) Cupola sign arrowheads c) Rigler's sign d) chest radiograph showing free air under the diaphragms
• 
  a.b)Pneumoperitoneum developed three days following percutaneous radiologic gastrostomy
• 
  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"^[32]

Differential diagnosis

Pseudopneumoperitoneum a) Chest radiograph of Chilaiditi syndrome showing large bowel loops arrow under the diaphragm b) linear atelectasis c) loculated air beneath the diaphragms following colonoscopy^[5]

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.

Treatment

Treatment depends on the cause.

Terminology

Pneumoperitoneum can be described as peritoneal emphysema,^[33] 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

External links