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(Radiology. 1999;213:113-117.)
© RSNA, 1999

Pediatric Imaging

Gastric Retention of Zinc-based Pennies: Radiographic Appearance and Hazards1

Sara M. O'Hara, MD, Lane F. Donnelly, MD, Emil Chuang, MB, BS, William H. Briner, BS and George S. Bisset, III, MD

1 From the Departments of Radiology (S.M.O., L.F.D., W.H.B., G.S.B.) and Pediatrics (E.C.), Duke University Medical Center, Erwin Rd, Box 3808, Durham, NC 27710. From the 1998 RSNA scientific assembly. Received January 12, 1999; revision requested February 18; revision received March 23; accepted April 29. Address reprint requests to S.M.O.


   Abstract
TOP
 Abstract
Introduction
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 References
 
PURPOSE: To determine the radiographic appearance and features of corrosion in U.S. coins exposed to gastric acid.

MATERIALS AND METHODS: Six U.S. copper-based pre-1982 pennies, 12 zinc-based post-1982 pennies, a quarter, a nickel, and a dime were exposed to postprandial concentrations of gastric acid (0.15N HCl) for 7 days, and radiographs were obtained daily. Half the zinc-based coins were scraped to disrupt their copper coating. Coins were weighed at the start and completion of the study.

RESULTS: Post-1982 zinc-based pennies developed radiolucent corrosive changes within 24 hours. Erosions on the coins became more apparent over time. Frank holes were present on day 2. The weights of these coins decreased 5%–8% during the study. Pre-1982 copper pennies and "silver-colored" coins showed no change on radiographs over 7 days.

CONCLUSION: Unexpected radiolucent corrosions may develop in post-1982 zinc alloy pennies when retained in the stomach. Coins have long been considered innocuous foreign bodies in the gastrointestinal tracts of children. However, because of the potential for ulceration and zinc-related morbidity, closer clinical and radiographic observation is warranted. Coins with scalloped edges or holes should be endoscopically removed, as they have likely been retained longer than 1 or 2 days.

Index terms: Children, gastrointestinal tract, 71.461, 72.461 • Foreign bodies, in air and food passages, 71.461, 72.461 • Stomach, ulcer, 72.259


   Introduction
TOP
 Abstract
 Introduction
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 References
 
In 1997, more than 21,000 pediatric patients were examined in U.S. emergency departments after swallowing coins (1). After the initial choking risk had passed, these coins were generally considered harmless during their short transit through the gastrointestinal tract (2). We became interested in this topic when a 2-year-old child underwent abdominal radiography in the emergency department of our institution after complaints of abdominal pain and vomiting 4 days after swallowing a coin. The time of coin ingestion was well documented, as his parents had witnessed him briefly choking on the coin and had taken him to the same emergency department for evaluation. His initial radiograph had shown an intact metallic disk (presumably a coin) in the stomach. The follow-up radiograph obtained 4 days later showed a metallic disk with a moth-eaten appearance retained in the stomach (Fig 1). Because the radiolucent erosions were not typical of a coin, other considerations included a button-type battery, toy part, or lead-containing object. Endoscopy performed the same day revealed a blackened, corroded 1989 penny and a subjacent bleeding ulcer (Figs 2, 3). After coin removal, the child was discharged and made a full recovery.



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  		Figure 1. Abdominal radiograph of a penny retained in the patient's stomach for 4 days that developed radiolucent holes and scalloped edges (arrow).

 


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  		Figure 2. Photograph of the corroded penny that was removed at endoscopy next to a shiny penny that, to our knowledge, had never been in a gastrointestinal tract.

 


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  		Figure 3. Endoscopic image of the peptic ulcer (arrow) found at the time of penny retrieval. Endoscopy revealed no evidence of gastric outlet obstruction.

 
We are aware of only two reports of similar cases in humans (3,4). The first report described erosions along the edge of a penny that had been lodged in a child's esophagus for an indeterminate length of time. The second report was of an adult patient receiving psychiatric care who died of multisystem organ failure and a zinc toxic reaction after massive coin ingestion. The corrosive reaction of pennies exposed to gastric acid has been linked to changes in the minting of pennies. Prior to 1982, pennies were forged of 95% copper and 5% zinc. Because of the increasing cost of copper, in October 1982 the U.S. Mint began making pennies with a zinc core (97.6% of volume) and a thin copper coating (2.4%) (5). We devised an experiment to test the effect of stomach acid on U.S. coins in the laboratory.


   MATERIALS AND METHODS
TOP
 Abstract
 Introduction
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 References
 
Four groups of coins were selected for evaluation: three silver-colored coins (one quarter, one nickel, and one dime); six pre-1982 pennies (worn from circulation, but not intentionally damaged); six post-1982 pennies in good condition; and six post-1982 pennies that had been intentionally damaged by scraping the edges and flat surfaces with a metal file until the zinc was visible in several spots. The penny retrieved from the 2-year-old child was also included in the study and weighed but was not subject to the in vitro experiment performed on the other coins.

Each group of coins was immersed in 50 mL of 0.15N hydrochloric acid in a 100-mL beaker. This concentration of hydrochloric acid approximates postprandial levels of gastric acid (6). The beakers were covered with laboratory plastic wrap and gently and continuously agitated with a Teflon-coated magnetic stirring bar (Bel-art Products, Pequannock, NJ) on a magnetic stirring plate (Corning, Corning, NY) at room temperature under a ventilation hood. The coins were rinsed and radiographed daily (63 kV, 8 mA; Kodak Insight Pediatric Imaging Film, Pediatric Ultra-Detail cassette; Eastman Kodak, Rochester, NY) and returned to beakers containing fresh acid solution.

The coins, acid solution, and radiographs were inspected daily, and observations were recorded (S.M.O.) regarding the shininess of the coins, the color and presence of sediment in the solution, and the radiolucencies of the coins on radiographs. Each group of coins was weighed (Alpha Century Balance; Mettler Toledo, Columbus, Ohio) at the start and completion of the 7-day study.


   RESULTS
TOP
 Abstract
 Introduction
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 References
 
Bubbles of gas indicating chemical reaction were seen immediately on the surface of the damaged post-1982 pennies and on day 3 on the undamaged post-1982 pennies. Bubbles were not seen on the silver-colored coins or pre-1982 pennies at any time. The surface of the initially shiny coins grew increasingly dull with time in all groups. Black sediment developed as the post-1982 pennies blackened and yellow sediment was visible as the silver-colored and pre-1982 pennies turned a dusty yellow.

Radiographically radiolucent erosions were visible on the post-1982 pennies within 24 hours of immersion in hydrochloric acid. Erosions along the edges of the coins that had been scratched with the metal file were most noticeable initially, creating a scalloped contour (Figs 4, 5). After 2 days of continuous exposure to acid, full-thickness holes developed through the flat surface of the pennies minted after 1982 (Fig 6). The largest holes were seen in one of the undamaged post-1982 pennies along the base of the Lincoln Memorial imprint (Fig 7). No radiolucent erosions or holes developed in the silver-colored coins or the pre-1982 pennies over the 7-day study (Fig 8).



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  		Figure 4. Radiograph of the pennies at the start of the experiment (from left to right, pre-1982 pennies, the penny swallowed by the patient, and post-1982 pennies). Two of the pre-1982 pennies in the radiograph were excluded to equalize the number of pennies in each group. Note that the six intentionally damaged coins in the last group are indistinguishable from the six undamaged coins.

 


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  		Figure 5. Radiograph of post-1982 pennies after 1 day in 0.15N hydrochloric acid. Damaged coins are on the left; undamaged coins are on the right. Erosions along the damaged edges of the coins (curved arrows) and some small erosions on the flat surfaces (straight arrows) are already visible.

 


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  		Figure 6. Radiograph shows the progressive corrosive changes in the post-1982 pennies after 2 days in acid solution (damaged on left, undamaged on right). Note the full-thickness holes (arrow) present in some of the undamaged coins along the imprint of the Lincoln Memorial.

 


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  		Figure 7. Photograph shows the full-thickness holes (arrows) that developed in one of the undamaged post-1982 pennies at the base of the Lincoln Memorial imprint.

 


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  		Figure 8. Radiograph of all coins exposed to acid solution after 1 week. Note that there is no appreciable damage to the quarter, nickel, or dime at the top of the image. The pennies at the bottom of the radiograph are grouped as pre-1982 copper pennies (left), intentionally damaged post-1982 zinc-based pennies (middle), and undamaged post-1982 zinc-based pennies (right). Note that the pre-1982 pennies on the left show no radiolucent erosions or holes.

 
The weights of the coins are recorded in the Table. All of the coins lost weight over the course of the experiment. The quarter, nickel, and dime lost 12% of their combined weight, likely reflected as the yellow-green sediment that formed in the beaker.

According to U.S. Mint specifications, nickels are forged of 25% nickel and 75% copper, while dimes and quarters are both composed of 8.33% nickel and 91.67% copper (7). The chemical reaction expected between these metal alloys and hydrochloric acid yields cuprous and cupric chloride and nickel chloride, which are yellow-green in color. The post-1982 pennies lost between 5% and 8% of their weight, likely as zinc chloride, the black sediment in the beakers. The penny retrieved from our patient weighed 26% less than expected, which far exceeded the weight lost in our in vitro experiment. The experimental post-1982 pennies each lost the equivalent of 81–185 mg of zinc.


   DISCUSSION
TOP
 Abstract
 Introduction
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
References
 
Coins are the foreign bodies most frequently ingested by children (7,8). Conservative treatment or watchful waiting is generally recommended in cases of coin ingestion once the anatomic narrowings of the cricopharyngeus muscle, thoracic inlet, aortic arch, and gastroesophageal junction have been successfully passed (2,9). The patient seen in our emergency department was treated within these guidelines and developed a peptic ulcer despite a lack of surgical history or evidence of gastric outlet obstruction at endoscopy. Given the electrochemical reaction that occurs between zinc and hydrochloric acid, post-1982 pennies may require closer surveillance or endoscopic removal.

The authors of the previously mentioned report (3) of corrosion of a penny impacted in the esophagus likely underestimate the reaction between gastric acid and zinc-based pennies. Two pennies were bathed in "hypochloric" acid for 6 weeks, resulting in only minimal corrosion. The acid solution's description as "hypochloric" is likely a typographical error; "hydrochloric" is probably intended. Even so, the concentration of the acid used in their study is an underestimation of postprandial concentrations of gastric acid, which may be further elevated by stress-related hypersecretion. Furthermore, the authors did not agitate the coins in the solution or replenish the acid solution during their study of several weeks duration.

Our technique had shortcomings in simulating conditions in the stomach; specifically, the coins in solution were not kept at body temperature (above 98°F [36.6°C]), and the acid solution was replenished only once daily. The differences in percentages of weight lost between our experimental coins and the patient's penny likely reflect these deficiencies.

The fraction of zinc available as absorbable ions varies with different zinc salts. At physiologic pH, this fraction is greatest for zinc chloride and zinc acetate (approximately 100%), with the fraction in zinc gluconate (30%) being next highest (10). The latter chemical formulation is found in over-the-counter cold-prevention lozenges, with 30 mg of zinc per lozenge (10).

The chemical reaction between gastric acid and post-1982 pennies yields a highly absorbable form of zinc, zinc chloride, which may have toxic effects. The patient seen in our institution's emergency department absorbed the equivalent of 22 cold-prevention lozenges from the penny he swallowed. Zinc toxicity has been reported on frequently in veterinary literature (12–14) and much less frequently in human medical literature.

Sources of zinc toxicity reactions in humans include liquid zinc chloride ingestion (15), parenteral nutrition (16), zinc supplements (17), coins (4,17,18), and metal toys (19). Pets, especially dogs, may be more sensitive to zinc toxicity, although this effect may also be related to milligrams of zinc per kilogram of body weight. A fatal toxicosis was reported in a 5-kg dog that had swallowed only two pennies (14).

The toxic effects of zinc absorption include local corrosion and ulceration of the esophagus and stomach, nausea, vomiting, hematemesis, and abdominal cramping (4,15,20). Systemically, excessive zinc absorption can cause nonregenerative anemia, hemolysis, and derangement of clotting factors (4,20,21). Zinc toxicosis has also been associated with pancreatic dysfunction, pancreatitis, and elevated amylase levels (4,15,17). It is reported to cause copper deficiency, hepatocellular necrosis (4,17,18,21), acute tubular necrosis and renal failure (4,15,16,20), and death from multisystem organ failure (4,16).

The corrosions along the surface of the post-1982 pennies exposed to gastric acid can mimic those of lead-containing foreign bodies and button-type batteries on abdominal radiographs. Metallic foreign bodies containing lead have been reported to cause lead intoxication and even death when retained in the gastrointestinal tract (22,23).

As with pennies, the threat from lead-containing objects is related to prolonged retention in the bowel. Two types of button batteries have been associated with adverse effects (24). Mercuric oxide cells have a greater propensity to fragment and release radiopaque droplets into the bowel. None of the patients with mercury droplets in the intestine had clinical signs of toxic effects of mercury, although blood levels were abnormal in some patients. Lithium cells are also hazardous due to their larger diameters and greater voltage. In general, batteries larger than 15 mm in diameter or those retained in the stomach for more than 48 hours are candidates for endoscopic removal (24). However, the overwhelming majority of ingested batteries and other foreign bodies pass safely through the intestinal tract with conservative management (24).

Although reports of eroded pennies in humans are few, the recognition of this occurrence may become increasingly important as the number of post-1982 coins in circulation increases and damage to their thin copper jackets occurs with normal wear. Awareness of the unusual scalloped border and holes that can develop in coins retained in the stomach should prompt endoscopic removal, as these coins have likely already been corroding in the stomach and causing gastric irritation for more than 1 or 2 days.


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  		Weight of Coins before and after 7 Days in Hydrochloric Acid
 


   Footnotes
 
Author contributions: Guarantor of integrity of entire study, S.M.O.; study concepts, S.M.O., W.H.B.; study design, S.M.O., L.F.D., W.H.B.; definition of intellectual content, G.S.B.; literature research, L.F.D., S.M.O.; clinical studies, E.C.; experimental studies, S.M.O., W.H.B., L.F.D.; data acquisition, S.M.O., W.H.B., L.F.D.; data analysis, S.M.O., L.F.D., G.S.B.; manuscript preparation, S.M.O.; manuscript editing, L.F.D., G.S.B.; manuscript review, all authors.


   References
TOP
 Abstract
 Introduction
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 References
 

  1. U.S. Consumer Product Safety Commission. 1997 annual report: data collection—national electronic injury surveillance survey Washington, DC: U.S. Consumer Product Safety Commission, 1997.
  2. American Society for Gastrointestinal Endoscopy. Guidelines for the management of ingested foreign bodies. Gastrointest Endosc 1995; 42:622-625.[Medline]
  3. Fernbach SK, Tucker GF. Coin ingestion: unusual appearance of the penny in a child. Radiology 1986; 158:512.[Abstract/Free Full Text]
  4. Bennett DR, Baird CJ, Chan KM, et al. Zinc toxicity following massive coin ingestion. Am J Forensic Med Pathol 1997; 18:148-153.[Medline]
  5. Federal Reserve Bank of Boston. Penny Points (pamphlet) 1997.
  6. Ganong WF. Review of medical physiology 18th ed. Stamford, Conn: Appleton & Lange, 1997; 459-461.
  7. The U.S. Mint. Circulating Coins: specifications ; Available at: www.usmint.gov /circulating.specifications.cfm. Accessed December 1998.
  8. MacPherson RI, Hill JG, Othersen HB, Tagge EP, Smith CD. Esophageal foreign bodies in children: diagnosis, treatment, and complications. AJR 1996; 166:919-924.[Abstract/Free Full Text]
  9. Schunk JE, Harrison AM, Corneli HM, Nixon GW. Fluoroscopic Foley catheter removal of esophageal foreign bodies in children: experience with 415 episodes. Pediatrics 1994; 5:709-714.
  10. Berthon G. Fraction of zinc available as zinc ions at physiologic pH 7.4 ; Available at: http://www.coldcure.com/html/fraction.html Accessed October 1998.
  11. Cold-Eeze. ; Available at: http://www.quigleyco.com. Accessed October 1998.
  12. Mautino M. Lead and zinc intoxication in zoological medicine: a review. J Zoo Wildl Med 1997; 28:28-35.[Medline]
  13. Murray S, Tell LA, Bush M. Zinc toxicosis in a Celebes ape following ingestion of pennies. J Zoo Wildl Med 1997; 28:101-104.[Medline]
  14. Meerdink GL, Reed RE, Perry D, Warfield TK. Zinc poisoning from the ingestion of pennies. Am Assoc Vet Diagn Proc 1986; 29:141-150.
  15. McKinney PE, Brent J, Kulig K. Acute zinc chloride ingestion in a child: local and systemic effects. Ann Emerg Med 1994; 23:1383-1387.[Medline]
  16. Brocks A, Reid H, Glazer G. Acute intravenous zinc poisoning. BMJ 1977; 2:1390-1391.
  17. Broun R, Greist A, Tricot G, Hoffman R. Excessive zinc ingestion. JAMA 1990; 264:1441-1443.[Abstract]
  18. Hoffman HN, Phyliky RL, Fleming CR. Zinc-induced copper deficiency. Gastroenterology 1988; 94:508-512.[Medline]
  19. Chunn VD. Metal toys containing zinc, and anemia in children. Clin Med 1973; 80:7-10.
  20. Fisher D. Zinc. In: Sullivan JB, Krieger GR, eds. Hazardous materials toxicology: clinical principles of environmental health. Baltimore, Md: Williams & Wilkins, 1992; 865-868.
  21. Meurs KM, Breitschwerdt EB, Baty CJ, Young MA. Post-surgical mortality secondary to zinc toxicity in dogs. Vet Hum Toxicol 1991; 33:579-583.[Medline]
  22. Hugelmeyer CD, Moorhead JC, Horenblas L, Bayer MJ. Fatal lead encephalopathy following foreign body ingestion: case report. J Emerg Med 1988; 6:397-400.[Medline]
  23. Durback LF, Wedin GP, Seidler DE. Management of lead foreign body ingestion. J Toxicol Clin Toxicol 1989; 27:173-182.[Medline]
  24. Litovitz T, Schimitz BF. Ingestion of cylindrical and button batteries: an analysis of 2382 cases. Pediatrics 1992; 89:747-757.[Abstract/Free Full Text]



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