Internal Medicine


Presence of free air within the peritoneal cavity

Presence of free air within the peritoneal cavity


Surgical pneumoperitoneum: Pneumoperitoneum induced Peritonitis

Leak of air and visceral contents contaminates the peritoneal cavity producing peritonitis that mandates surgery
  • Inflammatory conditions
  • Traumatic injury: Intra-abdominal viscus perforation (M/C, 90% cases)
  • Neoplasia
  • Anastomotic leak
  • Vascular causes

Non-surgical/spontaneous pneumoperitoneum (SP):

Presence of free air in the peritoneum with intact gut
  • Intrathoracic causes: Intermittent positive-pressure ventilation, asthma, chronic obstructive pulmonary disease (COPD), cardiopulmonary resuscitation, and severe coughing spells
  • Intra-abdominal causes: Pneumatosis cystoides intestinalis, following abdominal surgery and endoscopy
  • Gynecologic causes: Sexual intercourse, predominantly post-hysterectomy, vaginal douching, insufflation, and pelvic inflammatory disease (PID)
  • Idiopathic pneumoperitoneum

Clinical features

The clinical presentation of the patients varies according to the site of perforation.

Features of peritonitis (if present):

  • Abdominal pain, vomiting, abdominal distension, constipation, fever, diarrhea
  • Tachycardia (pulse >110/min)
  • Hypotension (systolic blood pressure <100 mmHg)
  • Oliguria (<30 mL/h)
  • Tachypnea (respiratory rate >20/min).


Chest radiograph:

  • Peritoneal ligament signs:
    • Silver’s sign/falciform ligament sign: Air outlines the falciform ligament.
    • Inverted V sign: Air outlining lateral umbilical ligaments (inferior epigastric vessels).
    • Football sign: Seen in massive pneumoperitoneum, where the abdominal cavity is outlined by gas.
    • Urachus sign: Outline of middle umbilical ligament.
  • Bowel signs:
    • Telltale triangle sign: Triangular air pocket between three loops of bowel.
    • Rigler’s sign/bas-relief sign/double-wall sign: Air outlining both sides of the bowel wall.
  • RUQ signs:
    • Cupola/saddlebag/mustache sign (supine radiograph): Air accumulation underneath the central tendon of the diaphragm in the midline.
    • Doge’s cap sign: Triangular collection of gas in Morison pouch.
    • Lucent liver sign: Reduction of liver opacity due to air located anterior to the liver.
(a) X-ray of abdomen, erect view, showing subdiaphragmatic free air (white arrows), air outlining the properitoneal fat stripe (black arrows) (b) Cupola sign (arrowheads) (c) Rigler’s sign (arrow) (d) Chest radiograph showing free air under the diaphragms (arrowhead) | Sureka, B., Bansal, K., & Arora, A. (2015). Pneumoperitoneum: What to look for in a radiograph?. Journal of family medicine and primary care, 4(3), 477–478.

Computerized tomography (CT):

Axial view of CT scan showing free intraperitoneal gas anterior to the liver and stomach. | Estridge, P., & Akoh, J. A. (2017). Recurrent spontaneous pneumoperitoneum: A surgical dilemma. International journal of surgery case reports, 30, 103–105.


  • Surgical pneumoperitoneum: Surgery
  • Spontaneous pneumoperitoneum: Often managed conservatively, and exploratory surgery is warranted only if the clinical features of peritonitis are present.

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