The authors review cases of foreign bodies introduced through accidental injestion, percutaneously,
rectally, or iatrogenically, either deliberately or by mishap. Radiologists must be able to recognize the
appearance of opaque and lucent foreign bodies, as well as diagnose complications of their presence.
Dr. Low is an Associate Professor and Dr. Killius is a Fellow in
the Abdominal Image Division of the Department of Radiology, Duke
University Medical Center, Durham, NC.
The majority of alimentary or abdominal foreign bodies occur due
to accidental ingestion. Most (80% to 90%) will pass uneventfully,
but others may cause obstruction or perforation depending on their
morphology and size.
Less commonly, foreign bodies may be introduced through other
routes or percutaneously. Finally, it is important to recognize
iatrogenic foreign bodies that may be introduced either
deliberately or by mishap during surgical, diagnostic, or
The objectives of radiography should be to recognize the
appearance of opaque and lucent foreign bodies, as well as diagnose
complications of their presence. There are also a few therapeutic
options available to the radiologist to assist patients with these
Ingested foreign bodies
An appropriate history is usually available, which will give a
key to the type of foreign body expected, as well as to the
expected site of obstruction or other symptoms. Bolus impaction in
adults is usually caused by animal or fish bones or by unchewed
boluses of meat
(figure 1). Occasionally, however, such history is not available
(especially in children, mentally incompetent, or uncooperative
patients) and 20% of patients may be asymptomatic
(figure 2). Indeed, when one foreign body is known to have been
ingested, consideration should be given to the possibility of a
Children usually impact with ingested and sometimes unwitnessed
coins, toys, or other foreign objects.
A foreign body may become impacted in the pharynx, which in turn
may cause choking or gagging because it is large or associated
Conversely, a foreign body impacted in the esophagus may be
regurgitated back into the pharynx with similar risk of airway
A crash cart for cardiopulmonary resuscitation must be immediately
available during assessment of these patients.
Approximately 70% to 80% of ingested impacted foreign bodies
will lodge in the pharynx or cervical esophagus.
This is particularly likely to occur with sharp objects such as
(figure 3A). When this is the suspected location of impaction, the
most useful initial study is a lateral soft-tissue view of the
It should be centered below the angle of the mandible with the
patient seated up-right, neck extended, shoulders low and
posterior. The patient phonating "Eeee" may prove useful to distend
the pharynx and improve visibility.
Regardless of optimal technique, it may be difficult to
differentiate small bone fragments from laryngeal cartilage
calcifications. A reference guide to the range of such
calcifications is of value in exploring this problem.
In the esophagus, favored sites of hold-up include the level of
the aortic arch, the left main bronchus, and the gastroesophageal
junction, especially when there is a pre-existing stricture
(figure 3B). A barium swallow may be required to find these
obstructed foreign bodies and is also warranted for follow-up after
the acute impaction is resolved to detect an underlying stricture
that is usually present.
A foreign body impacted in the pharynx or esophagus is unlikely to
pass spontaneously, and warrants immediate removal.
Once in the abdomen, the foreign body may stop at the gastric
pylorus (usually if it is thicker than 2.0 cm and longer than 5.0
cm), fail to traverse the duodenal sweep (usually if it is long,
>10 cm), or obstruct at the ileocecal valve.
Again, a pre-existing stricture may make passage of the body
difficult (figure 4).
The nature of the offending foreign body is important to its
detection and management. Metal or bony material are easily seen.
Similarly, lead-containing glass or crystal may be visible. Plastic
or wood is almost always a challenge unless there is some adherent
lead paint. Fish bones are usually a problem, as they are often
sharp and cause considerable irritation, and are variably opaque.
Other sharp and pointed objects (e.g., other meat bones,
toothpicks, razors, and pins) are at risk of perforating the gut
(figure 5). Sometimes, the penetrating object may seal the
perforation and prevent leakage of bowel content until it is
Ideally, such objects should be removed while still in the stomach.
Metallic ingested foreign bodies require special consideration
in their management. The acid of the stomach may react chemically
with the metal and result in mucosal inflammation, ulceration, and
perforation. Similarly, gastric acid may break the seal of an
ingested battery, leading to corrosive toxicity. This is of
particular concern with miniature alkaline batteries. These
batteries are in common use in electronic devices and toys and are
small and easily swallowed.
Break down of the swallowed battery allows discharge of its
contents. They may contain strong concentration (40% to 45%) sodium
or potassium hydroxide, which has been reported to be responsible
for perforation by alkali necrosis of the esophagus, stomach, and
small bowel Meckel's diverticulum with serious or fatal
The chemical toxicity of heavy metals that may be contained within
some of these batteries is also of concern. Silver, manganese,
cadmium, nickel, zinc, and lithium are all used in their
composition. Mercury is another consideration as it may be absorbed
into the circulation
(figure 6). The amount of mercury (usually in the form of elemental
mercury or as mercuric oxide) within a battery ranges from 0.09 to
21 g. The lethal dose of the toxic form of mercury (as chloride or
oxide) for humans is not known exactly, but is estimated to be 1.0
to 4.0 g.
Coins have traditionally been considered relatively inert in
their chemistry. A dime (17 mm) or a penny (18 mm) will usually
pass through the intestinal tract if there is no hold up in the
pharynx or esophagus.
In 1982, the copper penny (95% copper, 5% zinc) was replaced by the
zinc penny (2.4% copper, 97.6% zinc). The zinc results in chemical
reactivity including the development of gastric erosions.
Swallowed, concealed illicit drugs (e.g., crack in vials,
cocaine in condoms) can produce a very confusing picture,
especially in the absence of a useful history from the patient.
These drug couriers, known as "mules" or "body packers," use the
gastrointestinal tract to smuggle their cargo undetected by the
custom authorities. Imaging may be called upon to examine these
suspects without physical intrusion. Occasionally, a courier may be
imaged without suspicion because of a medical presentation (such as
may occur if a package is disrupted resulting in drug intoxication,
or if the packages result in a bowel obstruction). On plain films,
bundles of cocaine are visible in up to 90% of cases and appear as
multiple uniformly round or oval densities (figure 7). The density
of the packet will vary with the wrapping material used (dense
aluminum foil versus lucent wax) and the processing of the
surrounding balloons or condoms (there may be a tiny amount of air
trapped between the layers, producing a lucent rim). In cases of
doubt, ultrasonography and computed tomography would be appropriate
to further define the suspect material.
A few therapeutic options are available for the radiologist to
assist in the management of some of these patients. A bolus
impacted at the gastroesophageal junction may pass spontaneously
during a barium swallow, aided by IV glucagon to relieve sphincter
spasm, and effervescent agents.
A Foley balloon catheter may be introduced and passed with
fluoroscopic guidance past the offending bolus. The balloon can
then be distended and the foreign body can be extracted from the
esophagus as the catheter is withdrawn.
Occasionally, a magnet-tipped probe can be passed fluoroscop-ically
into the esophagus or stomach to retrieve a metal foreign body.
Considerable care must be taken with impactions of >24-hour
duration because of the potential for esophageal perforation from
A few pathological conditions may produce a radiographic
appearance mistaken for foreign bodies. The presence of intestinal
infestation by Ascaris lumbricoides may produce a radiographic
appearance mistaken for foreign bodies (fragments of catheter or
other tubing). These parasites appear as long, thin, tubular
filling defects in the bowel (figure 8). They might be particularly
confusing when seen on CT, as the worm will only be seen in small
sections on multiple images.
Sonography of ascariasis has also been described; this modality is
useful in its ability to visualize the curling movements of the
worms, establishing the diagnosis with certainty.
Luminal filling defects may also be seen with bezoars (figure 4C),
gallstone ileus (figure 9), and polypoid tumors.
Parenterally inserted objects
Objects may reach the abdominal cavity or alimentary tract
through the anus, urogenital canal (figure 10), or percutaneously,
either deliberately or accidentally.
An obvious history is usually forthcoming, which will aid in the
identification of the presence or absence of the suspected foreign
body. Occasionally, such information is withheld (figure 11),
either due to patient embarrassment or to avoid criminal
Iatrogenic foreign bodies
Deliberately retained surgical clips are well recognized.
Inadvertently retained material include laparotomy pads, sponges,
Penrose drains, needles, hemostats, and forceps
(figure 12). Nonopaque surgical material, such as sponges, always
include radiopaque markers in their manufacture
(figure 13). Occasionally, these are left intentionally to maintain
hemostasis, especially if postoperative oozing is anticipated. They
should be removed either before the closure of the operation or at
re-exploration soon after.
A retained surgical sponge may result in development of an
inflammatory mass, a gossypiboma.
Increasing use of enteric and vascular catheters and other
devices will require recognition to identify the correct location
or misplacement. The most serious potential misadventure of a
feeding catheter or nasogastric tube is placement in the
tracheobronchial tree, which can lead to life-threatening
pneumothorax, especially when the tube is removed.
The malposition of the tube may also go unrecognized as the device
may only be visible on the periphery of the field of view of an
abdominal radiograph (figure 14).
The historical use of Thorotrast as an intravascular contrast
mediumwith resultant permanent retention of the dense material
within the reticuloendothelial system of the liver, spleen, and
lymph nodesmay result in a bizarre appearance of the abdominal
radiograph to the unwary
(figure 15). Intravenous injection with mercury has been reported
and will produce a similarly strange appearance with droplets of
the liquid metal visible in the liver, kidneys, lungs, and gut.
Thorotrast was also used to opacify hollow organs with resultant
permanent retention of the material under the epithelial surface,
such as renal opacification after retrograde pyelography.
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