Gastrointestinal perforation x-ray

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mohammed Abdelwahed M.D[2] Template:Gastrointestinal perforation x-ray

Overview

Pneumomediastinum

The "V" sign of Naclerio is free air in the mediastinum outlining the diaphragm and is seen in approximately 20 percent of cases [97].

Ring-around-the-artery sign -Widening of the mediastinum is sometimes seen with esophageal perforation. •Free air under the diaphragm on upright films

Pleural effusion may represent leaked esophageal contents

Pneumothorax is a rare finding in esophageal perforation and is thought to occur by the spread of gas along tissue planes Subcutaneous emphysema may be seen in some cases.

Chest CT

Pneumothorax, pneumomediastinum, pleural effusion, mediastinal abscess.

Abdominal imaging

Plain abdominal films

The appearance of pneumoperitoneum on plain films depends on the location of the air and patient positioning. Air outside the gastrointestinal tract (pneumoperitoneum) can be located freely in the peritoneal cavity, in the retroperitoneal spaces, in the mesentery, or in ligaments of organs. Extraluminal air may not be apparent if the perforation is small, has self-sealed, or has been contained by adjacent organs. Nonsurgical sources can also cause air in the peritoneal cavity

Free air under the diaphragm in upright abdominal films (image 3), air over the liver (right lateral decubitus) or spleen (left lateral decubitus), anteriorly on supine films (football sign).

Cupola sign (inverted cup) is an arcuate lucency over the lower thoracic spine [98]

Rigler sign (double-wall sign) is seen as gas outlines the inner and outer surfaces of the intestine

Psoas sign is air in the retroperitoneal space outlining the psoas muscle.

Urachus sign is air in the preperitoneal space outlining the urachus or umbilical ligaments.

Abdominal CT

Signs of perforation on abdominal CT scanning include extraluminal air (image 6); extraluminal oral contrast; free fluid or food collections; and discontinuity of the intestinal wall, fistula, or intra-abdominal abscess often associated with irregular adjacent bowel wall thickening [82,93,99,100].

Neck imaging

Plain films

Signs of perforation on plain neck imaging include subcutaneous emphysema tracking into the neck (image 2), anterior displacement of the trachea, and air in the prevertebral fascial planes on lateral view (image 7).

Additional studies may be indicated as a means to further investigate a suspected perforation in a specific organ. Other imaging studies include endoscopy (upper, lower), esophagography, upper gastrointestinal series, ultrasound, contrast enema, and dye studies [101].

It is important to note that for suspected perforation, barium should not be used initially as an oral contrast agent because it can produce granulomas in the tissues if it leaks out, and it can obscure abdominal findings on other imaging studies [101].

However, if extravasation has not been demonstrated on initial water-soluble contrast studies and suspicion for perforation remains high, barium can be administered orally or transrectally depending on the suspected site of perforation, provided additional CT or arteriography is not planned [102].

Endoscopy is an important tool for evaluating patients with suspected esophageal perforation, particularly following instrumentation, or related to noniatrogenic trauma [103,104]. Endoscopy allows direct inspection of the perforation and, in some cases, a therapeutic option. Endoscopy may show local erythema or spasm and essentially excludes the presence of the mucosal lesion. The disadvantage is the potential for causing a perforation with instrumentation. Nevertheless, in most cases, CT is obtained first because of its sensitivity and wide availability [105].

Dye studies may be useful for evaluating patients with a pleural effusion and a thoracostomy tube who are suspected to have an esophageal leak. Methylene blue introduced cautiously via a nasoesophageal tube will make or confirm the diagnosis by causing blue discoloration of the chest tube drainage.

Esophagus

Plain radiograph

Possible cues on chest radiographs include:

pneumomediastinum, abnormal cardiomediastinal contour, pneumothorax and pleural effusion are all features, although non-specific, for oesophageal perforation 5 • widening of the mediastinal shadow: non-specific on its own

Fluoroscopy

most sensitive within the first 24 hours 1

patient examined semi-supine on fluoroscopy table

a water-soluble agent should be used initially as barium can cause mediastinitis

oesophageal perforation may be represented as mucosal irregularity or gross extraluminal contrast extravasation

some authors suggest the use of small amounts of low or high concentrations of barium if no leak is evident on initial screening with water soluble contrast 8

CT

The role of CT is usually to look for stigmata of perforation when fluoroscopy is equivocal, and there is persisting suspicion of perforation. These include

extraluminal gas locules in the mediastinum or abdominal cavity, adjacent to the oesophagus are highly suggestive 2, 4

pleural or mediastinal fluid

pneumomediastinum or pneumothorax

pericardial or pleural effusions can be seen Water soluble oral contrast can be administered 20 minutes before scanning to demonstrate extravasation. Intravenous contrast is usually administered to delineate the oesophageal wall (25 - 60 second delay) 8.

Intestinal perforation

Plain radiograph

free gas under the diaphragm is a classic sign of pneumoperitoneum on erect chest and abdomen radiographs and it is suspicious for bowel perforation

other signs of pneumoperitoneum, including Rigler's sign

CT

this is the primary imaging modality for detection and localization of bowel perforation

the site of the perforation can often be localized by:

tracking the bubbles of pneumoperitoneum toward a region of bowel

looking for localised peritoneal fat stranding or bowel wall thickening o determining a site of bowel wall discontinuity

if the patient received oral contrast, then often the leak can be seen directly as contrast spills out of the perforation site

if a suspected bowel perforation is the primary indication for the study, then protocolling the study with a water-soluble contrast medium is useful

if a bowel perforation occurs due to obstruction, the perforation usually occurs at the site of maximal bowel distention and the perforation may be distant from the actual cause of the bowel obstruction

a bowel perforation may not result in pneumoperitoneum, but liquid contents exiting the bowel may form a phlegmon or abscess

Ultrasound

although not a primary modality for evaluating pneumoperitoneum, free gas can be detected on ultrasound when gas shadowing is present along the peritoneum

make sure that the gas is not within the colon before deciding on calling pneumoperitoneum

Fluoroscopy

suspected gastroduodenal perforation

an upper GI study with water-soluble contrast medium is not usually the primary study for detection of a suspected gastric or duodenal perforation but can be useful for confirmation of an equivocal appearance on CT or for detection of the precise location of a small perforation

suspected small bowel perforation

small bowel follow through is inferior to CT of the abdomen and pelvis with oral contrast for detection and localization of small bowel perforation

suspected colonic perforation

single contrast barium enema is not usually appropriate in the setting of colonic perforation

the reason for colonic perforation is usually apparent and these patient are usually operated upon emergently