Pneumoperitoneum Imaging

8/13/2019 Pneumoperitoneum Imaging

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IntroductionPneumoperitoneum 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. This pageprovides an overview of the plain film diagnosis of pneumoperitoneum.

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

Plain Film Signs of PneumoperitoneumRadiographers are more likely to demonstrate pathologies that they are familiar with. As James Begg stated, sometimes you have to 'work to demonstrate pneumoperitoneum'.

What he meant bythis is that the supine signs of pneumoperitoneum may be subtle- the radiographer must be able to identify the signs on the supine image and know whatsupplementary views will prove the existence of free intraperitoneal gas.

The plain film signs of pneumoperitoneum are well established in the literature as follows

RUQ/liver signs on supine AXRThere are 3 separate signs of free air around the liver as follows.

Pneumoperitoneum: Importance of Right Upper Quadrant Features

LESLIE MENUCK AND PAUL I. SIEMERSAmJ Roentgeno! 127:753-756. 1976

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

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Pneumoperitoneum

The Radiological signs of pneumoperitoneum are among themost important signs in radiology, indeed in Medicine.Sometimes the amount of free gas is small and you may haveto work to demonstrate it (i.e. modify the film technique). Missit and the patient may die

Abdominal X-rays made easy. 2nd edition, James D. BeggChurchill Livingstone, Elsevier, 2006

p94

We diagnose what we look forand look for what we know

1 Anterior Subhepatic Space Air

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

3 Air Anterior to Ventral Surface of Liver

4 Riglers sign on supine AXR (also known as double-wallor bas-reliefsign)

5 Falc iform Ligament Sign

6 The football s ign

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

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

13 Abscess Gas

14 Pneumoretroperitoneum

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

The differentiation between fat and air density becomes easier withexperience. This image of normal fat surrounding the liver shows a

Pneumoperitoneum

PneumoperitoneumCases

The Abdominal Plain Film-Terminology

Small Bowel ObstructionNeonatal Lines, Tubesand Catheters

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2. Doges Cap Sign(RUQ sign 2)

3. Air Anterior to Ventral Surface of Liver(RUQ sign 3)

Pneumoperitoneum: Importance of Right Upper Quadrant FeaturesLESLIE MENUCK AND PAUL I. SIEMERS

AmJ Roentgeno!127:753-756. 1976

consistent density continuous with the properitoneal fat stripe.

Pneumoperitoneum: Importance of Right Upper Quadrant FeaturesLESLIE MENUCK AND PAUL I. SIEMERS

AmJ Roentgeno!127:753-756. 1976

Doges Capsign refers to free air in Morrison's pouch. Morrison's pouch is normally a potential space betweenthe 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 easilymisinterpreted as gas in the duodenum.

Gas in Morrison's pouch may have the following features

Triangular in shapeconcave medial borderpositioned inferior to the right 11th ribpositioned superior to the right kidney

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

http:// bp3.blogger.com/_iAsK5lmVXqM/Rpn6Q091zNI/AAAAAAAAAQE/qDaIjgpsZa4/s320/doge.jpg

Morrisons pouchfree gas demonstrated on supine Radiographs typically show the following Characteristics1.Typically triangular shaped2.The lower lateral corner is commonly sharp3.The lateral border is typically concave and outlines the medial border of the liver4.It is positioned inferior to the 11thrib

5.It is positioned superior to the right kidney

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. Ifthe liver is seen to demonstrate an uneven density, pneumoperitoneum should be considered.

Note also Rigler's sign

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4. Decubitus Abdomen Sign

5. Riglers Signon supine AXR

6. Falciform Ligament Sign

7. The football sign

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

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

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

The falciform ligament connects the anterior abdominal wall to the liver. The ligament continues to extendinferiorly beyond the liver where it becomes the round ligament (white arrow). Given that the falciform ligamentis situated against the anterior abdominal wall, it is not surprising that it becomes outlined with air in a supinepatient with free abdominal gas.

This is an axial CT scan image of a patient withpneumoperitoneum. The free gas is seen outlining the anteriorabdominal wall and several loops of bowel. The arrowedstructure is the falciform ligament surrounded by freeintraperitoneal gas.

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

The football sign likens the massively air-filled peritoneum to an American football. To extend the simile a littlefurther, the falciform ligament has been likened to the seam in the football, and the rarely seen medial andlateral 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.

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8. Continuous Diaphragm Sign

9. Double Bubble Sign

10. The Cupola Sign.

11. Lesser Sac Gas

http:// shop.sportsmanswarehouse.com.au/images/product_images/1660/foot001.jpg

John W. Rampton, MDThe FootballSign

(Radiology 2004;231:81-82.) RSNA, 2004

image source unknown

Another manifestation of massive pneumoperitoneum is the continuous diaphragm sign. Where there issufficient air beneath the diaphragm, the continuous nature of the diaphragm is demonstrated. Note that the leftand right hemidiaphragms contrasted by the free gas appear as a continuous structure.

The double bubble signis an appearance of subdiaphragmatic gas under the left hemidiaphragm in which thereare two collections of overlapping gas- one of these collections is subdiaphragmatic free gas and the other isnormal gas within the fundus of the stomach. Note that the diaphragm (black arrow) is a thinner walledstructure than the stomach wall (white arrow). This distinction is sometimes useful in distinguishing betweenthe two structures.

Note also free subdiaphragmatic gas under the right hemidiaphragm

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

The term cupola comes from a dome such as this famous dome ofthe Duomo in Florence.

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12. The Triangle Sign

12. The OthersThere 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.

13. Abscess Gas

14. Pneumoretroperitoneum

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

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

Sign Notes Reference

Leaping Dolphins Sign Air under hemidiaphragm and diaphragmatic muscle slips visible http://www.thaigastro.com/book/file/Thai-Journal-of-gastroenterology-vol-6-no-3-627306.pdf

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

google

The Inverted V Sign "in infants the inverted V is undoubtedly caused by the large umbilical arteries, inadults I believe it is the inferior epigastric vessels that produce the inverted V sign.

The Inverted V Sign of PneumoperitoneumJohn F. Bray, M.B., Ch.B., F.R.C.S. (Ed.),F.R.C.R.2Radiology 1984; 151: 45-46

Air in the Fissure for theLigamentum Teres

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

Radiology; 1991. 178: 489 - 492

Coronary Ligament Outlined by Air The coronary ligament is sited anterior to the liver. http://myweb.lsbu.ac.uk/dirt/museum/margaret/752-712-1000221.jpg

Pneumo-gall bladder Air in the gall bladder fossa outlining the gall bladder google

This patient has an abscess (proven on CT). The arrowed bubbles of gas are suspicious in that they are notclearly 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.

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Case 1

This patient has free air in the retroperitoneal space. The air is seen surrounding the lateral border of the rightkidney (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 viewto 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 (blackarrow).

This in-patient was referred for chest radiography followingopen mitral valve surgery. There appears to be free air underthe right hemidiaphragm. This was interpreted as 'colonicinterposition' (Chilaiditis sign) but I suspect that it is a 'leapingdolphins sign'. The appearance of septa within the air collectionunder the right hemidiaphragm is probably outlining the costal

muscle slips of the hemidiaphragm rather than representingoutline of bowel wall.

There also appears to be a negative 'silhouette sign' of the liver(black arrow).

There is an azygous lobe (white arrow).

There is a pleural effusion on the left.

Quoted fromMorton A. MeyersDynamic radiology of t he abdomen: normal and pathologic anatomy

The lateral chest image similarly demonstrates a negative'silhouette sign' involving the liver (black arrow).

There appears to be a triangle of pleural fluid at the base of aninferior acc essory fissure.

There are three metallic rings associated with the mitral valvesurgery.

There is loss of visualisation of the left hemidiaphragm

associated with a left pleural effusion.

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Case 2

Discussion

This 78 year old man presented to the Emergency Department with ahistory of abdominal pain. He was examined and referred for an acuteabdominal and chest X-ray examination.

There appears to be gas under the right hemidiaphragm. Note that thereis bowel gas superimposed over the liver suggesting colonic interposition-a known cause of false pneumoperitoneum. If this appearancerepresented pneumoperitoneum, you would expect to see air-contrastedliver.

The lateral chest projection image demonstrates the appearance again ofair under the right hemidiaphragm. The is an associated air-fluid level.This appearance is more likely to indicate colonic interposition thanpneumoperitoneum. Where there is a clinical question ofpneumoperitoneum, a decubitius abdominal plain film would be helpful.

Pneumoperitoneum Pneumothorax Colonic Interposition

It is useful to be able to distinguish between the appearance ofair under the right hemi-diaphragm, colonic interposition andpneumothorax.

This paient has a pneumothorax. The right hemidiaphragmcontrasted with air in the pleural space resembles the livercontrasted with free air in the peritoneum(left)

This appearance of colonic interposition does bear somesimilarity to the appearance of pneumoperitoneum (aboveleft).

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Case 3

Case 4

The black arrow identifies the aircontrasted liver. Theaircontrasted costal muscle slip is marked with a white arrow

The white arrowed structure is probably a haustral markingand the black arrowed structure is diaphragmatic

This is a 60 year old lady with known Crohn's disease andabdominal pain. She was referred for an abdominal plainfilm. The large bowel wall is visible along both flanks. Theliver is also outlined by fat.

There is fat interposed between the inferior border of theliver and the hepatic flexure of the colon (white arrow)

There is properitoneal fat contrasting the caecum (blackarrow)

These appearances are not associated withpneumoperitoneum. The scattered air densities over the

liver probably represent air within bowel.



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This is a supine bedside chest X-ray image post intubation. At a cursary glance there may appear to be air under the right hemidiaphragm

This is in fact air above the diaphragm rather than under it. This patient has a right sided pneumothorax with a deep sulcus sign. The pneumothorax is also visible at the right lung apex(arrowed)



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Pneumoperitoneum Imaging

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