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Learning Radiology > Ch.15 - Recognizing Extraluminal Air in the Abdomen > Flashcards

Ch.15 - Recognizing Extraluminal Air in the Abdomen Flashcards

1
Q

3 key signs of pneumoperitoneum are:

A
  1. Air beneath the diaphragm.
  2. Visualization of BOTH sides of the bowel wall - Rigler sign.
  3. Visualization of the falciform ligament.
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2
Q

MCC of free air:

A
  1. Perforated peptic ulcer.
  2. Trauma whether accidental or iatrogenic.
  3. Perforated diverticulitis.
  4. Perforated appendicitis.
  5. Perforation of a colon carcinoma (rare).
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3
Q

Key signs of extraperitoneal (retroperitoneal) air:

A
  1. Streaky, linear appearance or a mottled, blotchy appearance outlining extraperitoneal structures and its relative fixed position.
  2. Moving little or not at all with changes in patient positioning.
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4
Q

Extraperitoneal air outlines extraperitoneal structures such as:

A
  1. Psoas muscles.
  2. Kidneys.
  3. Aorta.
  4. IVC.
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5
Q

Causes of extra-peritoneal (retroperitoneal) air include:

A
  1. Bowel perforation 2o to either inflammatory or ulcerative disease.
  2. Blunt or penetrating trauma.
  3. Iatrogenic manipulation.
  4. Foreign body digestion.
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6
Q

Key signs of air in the bowel wall include:

A
  1. Linear radiolucencies paralleling the contour of air in the adjacent bowel lumen.
  2. Mottled appearance that resembles air mixed with fecal material, or uncommonly, globular, cystlike collections of air that parallel the contour of the bowel.
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7
Q

Causes of pneumatosis intestinalis (air in the bowel wall):

A
  1. Rare primary form –> Pneumatosis cystoides intestinalis.
  2. More common 2o form:
    a. Necrotizing enterocolitis - Infants.
    b. Ischemic bowel disease - Adults.
    c. Obstructing lesions of the bowel –> Hirschprung, obstructing carcinoma in adults.
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8
Q

Signs of air in the biliary system:

A
  1. Tubelike, branching lucencies in the RUQ overlying the liver which are central in location + few in number.
  2. Gas in the lumen of the gallbladder.
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9
Q

Causes of pneumobilia:

A
  1. Incompetence of the sphincter of Oddi.
  2. Prior sphincterectomy.
  3. Prior surgery that results in the reimplantation of the CBD into another part of the bowel.
  4. Gallstone ileus.
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10
Q

3 findings in gallstone ileus:

A
  1. Air in the biliary system.
  2. SBO.
  3. Visualization of the gallstone itself.
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11
Q

4 MC locations of extraluminal air are:

A
  1. Intra-peritoneal (pneumoperitoneum - frequently called free air).
  2. Retro-peritoneal air.
  3. Air in the bowel wall (pneumatosis).
  4. Air in the biliary system (pneumobilia).
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12
Q

4 MC locations of extraluminal air are:

A
  1. Intraperitoneal (pneumoperitoneum) –> Free air.
  2. Retroperitoneal air.
  3. Air in the bowel wall (pneumatosis intestinalis).
  4. Air in the biliary system (pneumobilia).
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13
Q

3 major sign of free intraperitoneal air arranged in the order in which they are most commonly seen?

A
  1. Air beneath the diaphragm.
  2. Visualization of BOTH sides of the BOWEL WALL.
  3. Visualization of the FALCIFORM LIGAMENT.
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14
Q

Free air is best demonstrated by …?

A

CT scan.

Most surveys of the abdomen begin with conventional radiographs –> Abdomen radiograph is a GOOD SCREENING.

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15
Q

Small amounts of air will NOT be visible on …?

A

Supine radiographs.

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16
Q

Free air is easier to recognize under the right or the left hemidiaphragm?

A

Under the right, because only soft tissue density of the liver is usually located there.

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17
Q

Free air is more difficult to see under the LEFT hemidiaphragm because …?

A

Air-containing structures, such as the fundus of the stomach and the splenic flexure, already reside in that location and may mask the presence of free air.

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18
Q

If the patient is UNABLE to stand or sit upright, then …?

A

Do a LEFT LATERAL DECUBITUS VIEW of the abdomen.

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19
Q

Free air under the right hemidiaphragm - Pitfall?

A

Chilaiditi syndrome.

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20
Q

What is Chilaiditi syndrome?

A

Occasionally, colon may be interposed between the dome of the liver and the right hemidiaphragm + may be mistaken for FREE AIR –> Careful search for HAUSTRAL FOLDS.

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21
Q

Solution for Chilaiditi syndrome?

A

Left lateral decubitus or CT.

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22
Q

Introduction of AIR into the peritoneal cavity enables us …?

A

To visualize the wall of the BOWEL itself since the wall is now surrounded on BOTH sides by air.

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23
Q

The ability to see BOTH sides of the bowel wall is a sign of free intraperitoneal air called …?

A

Rigler sign.

24
Q

Rigler sign usually requires …?

A

Large amounts of free air in order to be present.

25
Q

Rigler sign can be seen on supine, upright, or prone films of the abdomen?

A

Either.

26
Q

Pitfall when seeing both sides of the bowel wall?

A

When dilated loops of small bowel overlap each other, they may occasionally produce the mistaken impression that you are seeing BOTH SIDES of the bowel wall.

27
Q

Solution of free air pitfall?

A

Confirm the presence of free air with:

  1. Upright view.
  2. LLD.
  3. CT.
28
Q

Visualization of the falciform ligament as a sign of?

A

INTRAPERITONEAL FREE AIR. (relatively large amount)

29
Q

In what position of the patient can we see the visualization of the falciform ligament?

A

When the patient is SUPINE.

30
Q

The football sign of free intraperitoneal air?

A

The curvilinear appearance of the falciform ligament –> Combined with the oval-shaped collection of air that collects beneath and distends the abdominal wall, has been likened to the appearance of a football with its laces –> The football sign.

31
Q

Summary - Three signs of free air - What do we require in order to be seen?

A

Air beneath diaphragm –> Upright position or LLD position + A horizontal x-ray beam (unless massive in amount).

32
Q

MCC of free intraperitoneal air is …?

A

Rupture of an air-containing loop of bowel, either stomach, small, or large bowel.

33
Q

What is the MCC cause of a perforated stomach/duodenum?

A

Perforated peptic ulcer –> STILL the MCC of free air.

34
Q

What does free air FOLLOWING PENETRATING trauma usually implies?

A

A perforation of the bowel –> NOT FREE AIR generated simply by penetration of the abdominal wall itself.

35
Q

Free air can remain for up to … days after surgery in an adult.

A

7 days.

36
Q

Perforated diverticulitis/appendicitis?

A

Usually produce walled-off abscess collections around the site of the perforation and rarely lead to significant amounts of free air.

37
Q

Perforation of a carcinoma …?

A

Is UNUSUAL –> Can also lead to free air.

38
Q

Signs of extraperitoneal air (retroperitoneal air)?

A
  1. Streaky linear appearance outlining extraperitoneal structures.
  2. A mottled, blotchy appearance (anterior pararenal space, especially).
  3. Relatively fixed position, moving little if at all with changes in patient positioning.
39
Q

Extraperitoneal air may outline extraperitoneal structures:

A
  1. Psoas muscle.
  2. Kidney, ureters, or bladder.
  3. Aorta or IVC.
  4. Inferior border of the diaphragm by collecting in the subphrenic tissues.
40
Q

Extraperitoneal air may extend through …?

A
  1. A diaphragmatic hiatus into the mediastinum –> Pneumomediastinum.
  2. To the peritoneal cavity through openings in the peritoneum –> Pneumoperitoneum.
41
Q

2 main causes of extraperitoneal air:

A
  1. Inflammatory disease (eg ruptured appendix).

2. Ulcerative disease (Crohn).

42
Q

4 other causes of extraperitoneal air:

A
  1. Blunt or penetrating trauma.
  2. Iatrogenic manipulation (perforation of the bowel during sigmoidoscopy).
  3. Foreign body (eg perforation of extraperitoneal ascending colon by an ingested foreign body).
  4. Gas producing infection originating in extraperitoneal organs (such as perforated diverticulitis).
43
Q

Air in the bowel wall is called?

A

Pneumatosis intestinalis.

44
Q

Air in the bowel wall is most easily recognized when …?

A

It is seen in profile producing a linear radiolucency (black line) whose contour exactly parallels the bowel lumen.

45
Q

Air in the bowel wall seen en face is …?

A

More difficult to recognize but frequently has a mottled appearance that resembles gas mixed with fecal material.

46
Q

Clues to help differentiate pneumatosis from fecal material:

A
  1. Presence of such mottled gas in the area of the abdomen unlikely to contain colon.
  2. Lack of change in the appearance of the mottled gas pattern over several images in DIFFERENT positions.
47
Q

Summary - 3 Signs of air in the bowel wall:

A
  1. Linear radiolucency paralleling the contour of air in the adjacent bowel lumen –> Occurs when air is seen in profile.
  2. Mottled appearance that resembles air mixed with fecal material –> May occur in an area of the abdomen not expected to contain colon; WON’T change over time.
  3. Globular cystlike collections of air that parallel the contour of the bowel –> Unusual benign condition usually affecting LEFT side of the colon.
48
Q

MCC of pneumatosis intestinalis in infants is?

A

Necrotizing enterocolitis –> Found mostly in premature infants in which the terminal ileum is most affected.

49
Q

Pneumatosis intestinalis can be divided into 2 major categories:

A
  1. Pneumatosis cystoides intestinalis (rare primary form).

2. A more common secondary form due to obstructive and necrotizing diseases.

50
Q

What happens in pneumatosis cystoides intestinalis?

A
  1. Affects LEFT colon usually.

2. Produces cystlike collections of air in the submucosa or serosa.

51
Q

Etiology of the more common secondary form of pneumatosis intestinalis?

A
  1. COPD - Presumably 2o to air from ruptured blebs dissecting through the mediastinum to the abdomen.
  2. Diseases in which there is necrosis of the bowel.
    a. Necrotizing enterocolitis in infants.
    b. Ischemic bowel disease in adults.
  3. Obstructing lesions of the bowel that raise intraluminal pressure.
    a. Hirschsprung.
    b. Pyloric stenosis.
    c. Obstructing carcinomas in adults.
52
Q

Important point regarding pneumatosis intestinalis associated with diseases that produce necrosis of the bowel and pneumatosis associated with obstructing lesions or COPD?

A

The FIRST is a more OMINOUS prognostic sign.

53
Q

Complications of pneumatosis intestinalis?

A
  1. Rupture into the peritoneal cavity –> Pneumoperitoneum.

2. Dissection of air into the portal venous system.

54
Q

3 signs of air in the biliary tract:

A
  1. Tubelike, branching lucencies in the RUQ overlying the liver.
  2. Tubular structures are central in location and few in number compared to portal venous air which is peripheral in location and fills innumerable vessels.
  3. Gas in the lumen of the gallbladder.
55
Q

When may gas in the biliary system be a normal finding?

A

If the sphincter of Oddi is OPEN (said to be incompetent).

56
Q

What other procedure may result in air in the biliary system?

A

Prior surgery –> Reimplantation of the common bile duct into another part of the bowel (ie choledocho-enterostomy) –> Frequently accompanied by gas in the biliary duct system.

57
Q

Pneumobilia can also be produced by?

A

Gallstone ileus –> Fistula between the bowel and the biliary system.

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