Pneumoperitoneum refers to free air within the peritoneal cavity most commonly caused by perforation of a hollow viscus from a procedure (e.g., endoscopy), trauma, cancer, bowel obstruction, inflammation, or ulceration. As this air accumulates outside of the GI tract, it compresses intraabdominal organs (beware of compartment syndrome) and respiratory distress due to decreased diaphragmatic excursion.
Patients may experience chest and abdominal pain, sepsis due to extravasation of bowel contents, or even limited symptoms if they have an impaired inflammatory response (e.g., on immunosuppressants). A chest radiograph with substantial pneumoperitoneum as pictured coupled with symptoms and the proper clinical context warrants immediate operative exploration. Patients who received intraoperative abdominal insufflation (e.g., laparoscopic cholecystectomy) may have residual air beneath their diaphragm postoperatively, but this is primarily carbon dioxide that will be reabsorbed over time.
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