Learning objectives
To provide an overview of the most frequent thoracic causes of pneumoperitonem with the relevant radiologic signs; to underline the importance of looking carefully under the diaphragm on the chest X-rays; to suggest the proper radiographic technique if pneumoperitoneum is suspected but not obvious.
Background
Pneumoperitoneum,
or air within the peritoneal cavity,
frequently indicates a perforated abdominal viscus that requires emergent surgical management.
Non-surgical spontaneous pneumoperitoneum (not associated with a perforated viscus) is an uncommon entity related to intrathoracic,
intra-abdominal,
gynecologic,
iatrogenic and other miscellaneous causes,
and is usually managed conservatively.
The most common thoracic causes include mechanical ventilation,
pneumomediastinum,
pneumothorax,
pre-existing pulmonary disease,
cardiopulmonary resuscitation.
For example,
mechanical ventilation with positive end-expiratory pressure (PEEP) may cause free air in the abdomen by alveolar rupture and subsequent air dissection into...
Imaging findings OR Procedure details
Three major findings:
Free air beneath diaphragm (crescent sign)
Visualization of both sides of the bowel wall (Rigler’s sign)
Normally,
only the inside of the bowel (the lumen) is visible unless free air outlines the outer surface of the wall
Visualization of the falciform ligament
Long vertical line to the right of midline extending from ligamentum teres notch to umbilicus; a common structure outlined on the supine abdominal X-Ray
Right upper quadrant (RUQ) gas (for small collections in supine position):
Anterior subhepatic space free air...
Conclusion
Recognizing the presence of pneumoperitoneum due to causes other than perforated viscus on plain chest and abdominal radiographs frequently may avoid unnecessary surgical exploration of the abdomen and its associated morbidity.
References
Chen MY,
Pope TL,
Ott DJ: Basic Radiology,
2nd ed.
LANGE Clinical Medicine,
2004
Menuck L,
Siemers PT,
Pneumoperitoneum: Importance of Right Upper Quadrant Features,
Am J Roentgenology 127:753-756,
1976
LearningRadiology.Com: Free Intraperitoneal Air
Mularski RA Sippel JM,
Osborne ML: Pneumoperitoneum: a review of nonsurgical causes,
Crit Care Med 28(7):2638-44,
2000
Personal Information
Elena Ilieva,
UMHATEM Pirogov,
Sofia,
Bulgaria