This is a 20 month old female who presents to the 
emergency department after swallowing a coin, 
according to two older children who were playing with 
her at the time.  They don't know what type of coin it 
was. Her mother has not noted any difficulty 
swallowing, drooling, or respiratory difficulty.
     Exam VS T37.1 (tympanic), P100, R36, BP 100/65, 
oxygen saturation 99% in room air.  Alert, active, no 
distress, no drooling.  Eyes clear,  TM's normal.  Oral 
clear, moist mucosa.  Neck supple.  Heart regular 
without murmurs.  Lungs clear.  No stridor, no 
wheezing, no coughing, no tachypnea, no retractions.  
Abdomen soft, flat, non-tender, bowel sounds active.  
Color, perfusion good.  Speech normal for age.  
Ambulating well.
     An AP radiograph of her trunk is taken.

View AP film.

     This radiograph shows a coin in her stomach.  
However, upon closer inspection, it has an unusual 
appearance.

View close-up of coin.

     The "coin" shows an internal ring just inside its 
perimeter.  This internal ring indicates that this is a disc 
battery, not a coin.  Since disk batteries (also called 
button batteries) have different GI consequences 
compared to coins, it is important to distinguish an 
ingested coin from a disc battery by history or 
radiographically.  Disc batteries will often have the 
characteristic internal ring appearance if taken in the AP 
direction.  If taken in the lateral position (on edge), it 
may show a bulge on one side (bilaminar appearance).  
When viewed obliquely, it may be difficult to distinguish 
a coin from a disc battery since none of these signs 
may be radiographically evident.

View lineup of disc batteries.

     This lineup shows a radiograph of a series of 6 disc 
batteries and a dime.  The first disc battery on the left 
has the positive terminal facing toward us.  The second 
battery from the left has its negative terminal facing 
toward us.  On this second battery, the black plastic 
insulator is visible in the photograph.  However, the 
radiograph of both the first and the second disc 
batteries show the internal ring sign of the plastic 
insulator.  The black plastic insulator on the first battery 
is on the other side of the battery.  The radiograph will 
still show the internal ring of the plastic insulator 
regardless of which way the battery is facing (AP or 
PA).  The fourth battery from the left also shows a 
plastic insulator, but the radiograph of this battery does 
not show the internal ring.  It could be absent because 
the battery casing is thicker than the first and second 
batteries.  Thus, the absence of the internal ring 
radiographically does not rule out a disc battery since 
the appearance of the internal ring is highly dependent 
on the degree of X-ray penetration, the angle of the 
battery, and the thickness of the battery casing.
     The third and fifth batteries from the left are viewed 
from the side.  On its side view, the battery has a 
rectangular appearance with a bulge on one end.  This 
bulge represents the negative terminal of the battery as 
shown in the corresponding photo below it.  The 
radiographic shadow also identifies this bulge which can 
be described as frosting on the cake (bilaminar 
appearance).  However, this radiographic sign may be 
absent if the battery is oriented obliquely, or if the 
battery is very thin.  The battery to the extreme right is 
oriented on edge.  The side view of this battery does 
not easily show the bulge of the negative terminal 
because this battery is very thin as can be seen in the 
photograph.
     Disc batteries contain various chemicals depending 
on the type.  Standard dry cell batteries contain 
zinc-carbon, alkaline, and nickel-cadmium compounds, 
but these are generally not found in disc batteries.  Disc 
batteries generally contain silver oxide, mercuric oxide, 
or lithium salts.  They may also contain concentrated 
caustics of potassium or sodium hydroxide.  Most disc 
batteries in use today are the silver oxide or lithium 
types.  However, many inexpensive or disposable child 
toys may still contain the less expensive mercuric oxide 
disc batteries.
     Disc batteries lodged in the esophagus can 
potentially cause serious problems in three ways:  1) 
Direct pressure necrosis (similar to coins or other inert 
foreign bodies).  2) Caustic injury due to the leakage of 
sodium or potassium hydroxide from a leaking battery.  
3) The esophagus can also sustain injury from low 
voltage burns from a disc battery that still has a charge. 
For these reasons, all disc batteries lodged in the 
esophagus should be removed expeditiously to avoid 
these injuries.
     Disc batteries that leak can also cause toxicity from 
the absorption of metal compounds.  Mercuric oxide 
batteries can potentially cause mercury poisoning 
resulting in gastritis, vomiting, and hypovolemic shock.  
This is not likely to occur for several reasons:  1) Most 
disc batteries do not leak.  They negotiate the GI tract 
and are passed intact in the stool.  2) Most of the 
mercuric oxide from old batteries is converted to 
insoluble metallic mercury which is not absorbed.  3) 
Any mercuric oxide that happens to leak out of the 
battery is converted to elemental mercury in the 
presence of gastric acids.
     Silver salts from silver oxide batteries may be 
corrosive, but they are minimally toxic.  Lithium is a 
highly reactive metal under extreme conditions such as 
fire.  Complications have not been reported in the 
literature following ingestion of a lithium disc battery.
     Most disc batteries will pass through the GI tract 
without difficulty.  A radiograph should be taken to 
localize the battery.  Esophageal batteries should be 
removed expeditiously.  If the battery is beyond the 
esophagus, the patient may be sent home and 
instructed to watch for symptoms of toxicity and 
passage of the battery in the stool by straining all 
stools.  Induction of emesis is generally not successful 
and it may be potentially harmful since the battery is 
potentially caustic.  A repeat radiograph is usually not 
indicated until 4 to 7 days after the ingestion if the 
battery has not been recovered.  Cathartics may 
accelerate passage of the battery.  If passage is 
delayed, the risk of leakage and the potential for 
complications depending on the contents of the battery 
must be assessed to determine the need for 
endoscopic or surgical removal.  Although most 
batteries will remain intact for two weeks or more, some 
batteries may have defective casings or they may be 
old and be leaking at the time the battery is swallowed.

References.
     Poisindex.  Volume 83, Expires 2/28/95.  Micromdex 
Inc.
     Kuhns DW, Dire DJ.  Button battery ingestions.  Ann 
Emerg Med 1989;18:293.
     Maves MD, Lloyd TV, Carithers JS.  Radiographic 
identification of ingested disk batteries.  Pediatr Radiol 
1986;16:154.
     Sheikh A.  Button battery ingestions in children.  
Pediatr Emerg Care 1993;9:224.
     Temple DM, McNeese MC.  Hazards of battery 
ingestion.  Pediatrics 1983;71:100.