[Radiologic pneumoperitoneum without perforation of a hollow viscus]

About 10% of the radiological pneumoperitoneums occur without hollow viscus perforation. Pseudopneumoperitoneum is defined when the subphrenic lucency does not correspond to free intraperitoneal air: subphrenic fat pad, linear lung atelectasis, abnormal subphrenic shape, Chilaïditi syndrome or subphrenic abscess. True pneumoperitoneum without hollow viscus perforation may result from diffusion of thorax-derived air through a phrenic defect or along sheaths of mediastinal blood vessels. The female genital tract represents another route for intraperitoneal air penetration. Other etiologies include iatrogenic pneumoperitoneum (after abdominal surgery and digestive endoscopy) and pneumatosis cystoides intestinalis, when the subserous intraparietal gaseous bubbles rupture into the peritoneal cavity.