PNEUMOPERITONEUMdonnalyn d. villarico,md

Pneumoperitoneum• Refers to the presence of free gas within the peritoneal

cavity. • The plain films signs of pneumoperitoneum are both

diverse and sometimes difficult to identify.

Why is Pneumoperitoneum Important?

• Pneumoperitoneum is most often caused by perforated abdominal viscus and can present an acute medical emergency.

The plain film signs of pneumoperitoneum

1 Anterior Subhepatic Space Air

2 Doges Cap Sign (free Air in Morrison's Pouch)

3 Air Anterior to Ventral Surface of Liver

4 Rigler’s sign on supine AXR (also known as double-wall or bas-relief sign)

5 Falciform Ligament Sign

6 The ‘football’ sign

7 The cupola. Air accumulation beneath the central tendon of the diaphragm

8 Continuous diaphragm sign

9 The triangle- air trapped between three loops of bowel

10 Air under diaphragm on erect cxr

11 Air outlined against liver/flank on decub AXR

12Other- diaphragmatic muscle slips, ligamentum teres air, Double Gastric Fundus sign, The Inverted-V sign, Scrotal air

13 Abscess Gas

14 Pneumoretroperitoneum

RUQ/liver signs on supine AXR

• There are 3 separate signs of free air around the liver.

1. Anterior Subhepatic Space Free Air (RUQ sign 1)

• Anterior subhepatic space free air tends to be vaguely linear in shape (arrowed). A visible medial border of the liver is often seen outlined by fat. A careful examination of this image (left) shows the arrowed density to be air density rather than fat density.

The differentiation between fat and air density becomes easier with experience. This image of normal fat surrounding the liver shows a consistent density continuous with the properitoneal fat stripe.

2. Doges Cap Sign (RUQ sign 2)

•This sign is known as Doges Cap sign. The Italian Doges wore this distinctively shaped cap. Gas in Morrison's pouch is only loosely shaped like a Doges cap and should not be taken too literally. Bear in mind that the "triangle Sign" was already taken!

2. Doges Cap Sign (RUQ sign 2) • Doges Cap sign refers to free air in Morrison's pouch. Morrison's pouch is normally a

potential space between the right kidney and the liver. This is a particularly difficult sign of pneumoperitoneum for several reasons. Firstly, it may be the only sign of pneumoperitoneum and may be very subtle. Secondly, it can be easily misinterpreted as gas in the duodenum.

Gas in Morrison's pouch may have the following features

Triangular in shape • concave medial border • positioned inferior to the right 11th rib • positioned superior to the right kidney

Morrison’s pouch free gas demonstrated on supine Radiographs typically show the following Characteristics

1.Typically triangular shaped 2.The lower lateral corner is commonly sharp 3.The lateral border is typically concave and outlines the medial border of the liver 4.It is positioned inferior to the 11thrib 5.It is positioned superior to the right kidney

3. Air Anterior to Ventral Surface of Liver(RUQ sign 3) • Air sitting against the ventral surface of the liver can be any shape and, as in this case,

is frequently "geographical" in shape. The liver is a homogenous organ and should be homogenous in density on plain film. If the liver is seen to demonstrate an uneven density, pneumoperitoneum should be considered.

Note also Rigler's sign

4. Decubitus Abdomen Sign

• This patient is in the left lateral decubitus position. It is conventional in radiography to mark the side the side that is up.

There is evidence of free air between the abdominal wall and the liver (white arrow). There is also evidence of free fluid in the peritoneum (black arrow).

5. Rigler’s Sign on supine AXR

• Rigler's sign is named after Leo G. Rigler. The sign refers to the appearance of the bowel wall on plain film when it is outlined by intraluminal and extraluminal air (arrowed). The extraluminal air is free peritoneal gas.

6. Falciform Ligament SignThe falciform ligament connects the anterior abdominal wall to the liver. The ligament continues to extend inferiorly beyond the liver where it becomes the round ligament (white arrow). Given that the falciform ligament is situated against the anterior abdominal wall, it is not surprising that it becomes

outlined with air in a supine patient with free abdominal gas. This is an axial CT scan image of a patient with pneumoperitoneum. The free gas is seen outlining the anterior abdominal wall and several loops of bowel. The arrowed structure is the falciform ligament surrounded by free intraperitoneal gas.

The falciform ligament sign is almost never seen in isolation. If there is enough free air to outline the falciform ligament, there is usually enough air to also provide at least a Rigler's sign. In this case(left), there is a Rigler's sign as well as RUQ signs. Note also bilateral nephrostomy tubes insitu.

7. The ‘football’ sign

• The football sign likens the massively air-filled peritoneum to an American football. To extend the simile a little further, the falciform ligament has been likened to the seam in the football, and the rarely seen medial and lateral umbilical ligaments are likened to the football laces.

This neonatal patient has massive pneumoperitoneum and could reasonably be said to display football sign. There is also falciform ligament sign, Rigler's sign and air in the scrotum.

8. Continuous Diaphragm Sign• Another manifestation of massive pneumoperitoneum is the continuous diaphragm

sign. Where there is sufficient air beneath the diaphragm, the continuous nature of the diaphragm is demonstrated. Note that the left and right hemidiaphragms contrasted by the free gas appear as a continuous structure.

9. Double Bubble Sign• The double bubble sign is an appearance of subdiaphragmatic gas under the left hemidiaphragm in which there are

two collections of overlapping gas- one of these collections is subdiaphragmatic free gas and the other is normal gas within the fundus of the stomach. Note that the diaphragm (black arrow) is a thinner walled structure than the stomach wall (white arrow). This distinction is sometimes useful in distinguishing between the two structures.

Note also free subdiaphragmatic gas under the right hemidiaphragm

10. The Cupola Sign.

• The term cupola comes from a dome such as this famous dome of the Duomo in Florence.

10. The Cupola Sign.

• The Cupola Sign refers to an air accumulation beneath the central tendon of the diaphragm (white arrows)

11. Lesser Sac Gas

• This image of free gas has a cupola sign (white arrows) and a lesser sac gas sign (black arrows). The lesser sac is positioned posterior to the stomach and is usually a potential space. There is free connection between the lesser sac and the greater sac through the foramen of Winslow.

12. The Triangle Sign

• The triangle sign refers to small triangles of free gas that can typically be positioned between the large bowel and the flank(black arrow)

12. The Others• There are a number of other signs of pneumoperitoneum that are less commonly seen. These

signs are sufficiently rare to not warrant close examination. Equally, for reasons of completeness, they have been included on this page

Sign Notes

Leaping Dolphins Sign Air under hemidiaphragm and diaphragmatic muscle slips visible

Urachus Sign

Air contrasted urachus. Appears as vertical line between bladder and umbilicus. Outline of medial umbilical ligament

The Inverted “V” Sign

" in infants the “inverted V” is undoubtedly caused by the large umbilical arteries, in adults I believe it is the inferior epigastric vessels that produce the “inverted V” sign.”

Air in the Fissure for the Ligamentum Teres

Air in the Fissure for the Ligamentum Teres. May appear in isolation. Appears as a lucent vertical stripe over liver

Coronary Ligament Outlined by Air

The coronary ligament is sited anterior to the liver.

Pneumo-gall bladder

Air in the gall bladder fossa outlining the gall bladder

13. Abscess Gas• This patient has an abscess (proven on CT). The arrowed bubbles of gas are suspicious in that

they are not clearly contained within normal hollow abdominal viscus. If they were, for example, contained within the colon, they would tend to be aligned in a more linear fashion and may outline normal haustral features.

14. Pneumoretroperitoneum

• This patient has free air in the retroperitoneal space. The air is seen surrounding the lateral border of the right kidney (white arrow). There is other evidence of free gas including Rigler's sign.

If you are not confident that the appearance is pneumoretroperitoneum, you can try an erect and decubitus view to

see if the gas moves. If the gas is seen to move, it's not in the retroperitoneum.

An axial CT scan image is shown with air around the right kidney (black arrow).

• Pneumoperitoneum is an important finding on plain film images. Untreated, pneumoperitoneum has poor morbidity and mortality outcomes. Radiographers who are familiar with the plain film appearances of pneumoperitoneum, particularly the supine image appearances, are more likely to undertake supplementary views to concusively demonstrate the pathology. Moreover, they will also have the opportunity to report the finding immediately to the referring doctor.

The inverted V sign

Urachus sign

Leaping dolphin sign

Diaphragmatic muscle slip sign is seen as a fewelongated, parallel, curving bands of linear opacityat right upper quadrant

Coronary ligament outlined by air

Pneumoperitoneum w/ peritonitis• Perforated viscus

Perforation of a peptic ulcer (gastric/duodenal) – mc cause

generally: absence of gas in the stomach + presence of gas scattered in the SI & LI = suggests a gastric perforation as a cause of pneumoperitoneum

Little or no colonic gas in the presence of a gastric gas-fluid level + small bowel distention = colonic perforation more likely

• Colonic perforations esp. Cecum – give the most abundant quantities of free intraperitoneal gas

• d/t obstructing malignancy or severe ulcerating colitis leading to toxic megacolon

etiology• Disruption of wall of hollow viscus

• Blunt or penetrating trauma• Perforating foreign body (eg, thermometer injury to rectum)• Iatrogenic perforation

• Laparoscopy / laparotomy (58%)• Absorbed in 1-24 days depending on initial amount of air introduced and body habitus

(80% in asthenic, 25% in obese patients)• Leaking surgical anastomosis• Endoscopic perforation• Enema tip injury

• Diseases of GI tract• Perforated gastric / duodenal ulcer• Perforated appendix• Ingested foreign-body perforation• Diverticulitis (ruptured Meckel diverticulum / sigmoid diverticulum, jejunal diverticulosis)• Necrotizing enterocolitis with perforation• Inflammatory bowel disease (eg, toxic megacolon)• Obstruction* (gas traversing intact mucosa): neoplasm, imperforate

anus, Hirschsprung disease, meconium ileus• Ruptured pneumatosis cystoides intestinalis• Idiopathic gastric perforation = spontaneous perforation in premature infants (congenital

gastric muscular wall defect)

etiology• Through peritoneal surface

• Transperitoneal manipulation• Abdominal needle biopsy / catheter placement• Mistaken thoracentesis / chest tube placement• Endoscopic biopsy

• Extension from chest• Dissection from pneumomediastinum (positive pressure breathing, rupture of bulla / bleb, chest surgery)• Bronchopleural fistula• Rupture of urinary bladder• Penetrating abdominal injury

• Through female genital tract• Iatrogenic• Perforation of uterus / vagina• Culdocentesis• Rubin test = tubal patency test• Pelvic examination• Spontaneous• Intercourse, orogenital insufflation

• Douching• Knee-chest exercise, water skiing, horseback riding

• Intraperitoneal• Gas forming peritonitis• Rupture of abscess• Air in lesser peritoneal sac gas in scrotum (through open processus vaginalis)