Multiple Magnet Ingestion as a Cause of Septic Peritonitis in a Dog

A 1 yr old, 3.8 kg, male castrated Yorkshire terrier was presented for emergency evaluation of lethargy, anorexia, vomiting, and diarrhea. Five days earlier, the owners had witnessed the dog chewing on a child's toy monkey. Magnets in the feet of the toy were noted to be missing after the dog chewed on the toy. The dog had been examined prior to presentation by his referring veterinarian. Abdominal radiographs performed on 2 consecutive days revealed two radiopaque objects in close proximity (approximately 2 mm) to each other, possibly in the small intestine. The abdominal organs appeared to be in their normal anatomic position and no evidence of small bowel dilation or obstruction was noted. There was mildly decreased abdominal detail in the area surrounding the radiopaque foreign objects (Figure 1). The dog was treated with amoxicillin^a, metoclopramide^b, and metronidazole^c and referred for further evaluation and treatment.

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On initial physical examination, the dog was quiet but responsive. His heart rate was 150 beats/min and his temperature was 39.7°C. He was approximately 5% dehydrated and pain was noted during abdominal palpation. The remainder of his physical examination was within normal limits. The CBC^d was within normal limits. A serum biochemical analysis^e,^f was within normal limits with the exception of an elevated alkaline phosphatase (240 U/L; reference range, 23–212 U/L) and a low blood glucose (72 mg/dL, reference range, 74–143 mg/dL). The blood glucose^g was rechecked approximately 1 hr later and was found to be within normal limits (92 mg/dL).

Treatment was initiated with crystalloid fluid therapy (Lactated Ringer's Solution^h) at a rate of 4 mL/kg/hr IV), systemic antibiotics (ampicillin-sulbactamⁱ, 20 mg/kg IV q 8 hr), and pain medication (buprenorphine^j, 0.01 mg/kg IV q 8 hr). Because the dog was pyrexic with vomiting and diarrhea, painful on abdominal palpation, and the radiographic foreign objects had no change in anatomic position on consecutive days, an exploratory laparotomy was performed. Anesthesia was induced with IV propofol^k to effect and a 6 mm endotracheal tube was placed. During surgery, the patient was maintained on isoflurane^l anesthesia and 100% oxygen. The rate of crystalloid fluid therapy was increased to 10.8 mL/kg/hr and a perioperative dose of cefazolin^m (22 mg/kg IV) was administered.

A ventral midline laparotomy was performed. The two radiopaque foreign bodies, identified as magnets, were found within the abdominal cavity adhered together in the omentum at the dorsal aspect of the left limb of the pancreas. There was a scant amount of fluid present, mostly in the caudal abdomen, and there was evidence of a focal peritonitis surrounding the magnets. It appeared that the magnets had perforated through the transverse colon and the greater curvature of the stomach. The perforations were approximately 4 mm in diameter, measuring slightly larger than the size of the magnets. Multiple omental adhesions in the region of the colonic perforation were noted. The magnets were removed from the omentum. The edges of the perforation in the greater curvature of the stomach were debrided and closed in two layers using 3-0 polydioxanone (PDS II) sutureⁿ in a simple continuous pattern. The edges of the colonic perforation were debrided and closed using 3-0 PDS II suture in a simple interrupted pattern. The omentum was tacked to the colonic serosa. The abdomen was liberally flushed with 2 L of sterile saline after an aerobic and anaerobic culture of abdominal fluid was obtained. A 7 mm Jackson-Pratt^o continuous suction drain was placed and anchored to the body wall using 2-0 Ethilon^p in a purse-string and finger-trap pattern.¹ New sterile surgical gloves and sterile instruments were used for the remainder of the abdominal closure. The linea alba was closed using 2-0 PDS II suture in a simple continuous pattern. The subcutaneous tissue was closed using 2-0 PDS II suture in a simple continuous pattern. The skin was apposed using 4-0 PDS II suture in an intradermal pattern as well as 3.5 mm sterile skin staples^q.

Ten minutes after surgery, the patient's PCV was 45% and total protein was 6 g/dL. The heart rate was 124 beats/min and his temperature was 35.8°C. Potassium chloride^r (20 mEq/L) was added to the crystalloid fluid therapy and the fluid rate was decreased to 4 mL/kg/hr. A warm fluid bolus of 250 mL of lactated Ringer's solution was administered in the perioperative period to help with the decreased body temperature and assist in the recovery period. The dog was hospitalized for 4 days following surgery and treated with buprenorphine (0.01 mg/kg IV q 8 hr), ampicillin^s (22 mg/kg IV q 8 hr), and enrofloxacin^t (5.4 mg/kg IV q 24 hr). The Jackson-Pratt drain evacuated approximately 216 mL of serosanguineous fluid over a 3 day period following surgery. Extracellular bacteria (1+ to 2+) per high-power field and degenerate neutrophils with no intracellular bacteria were seen on cytology of the fluid collected from the drain within 24 hr of surgery. Three days following surgery, the Jackson-Pratt drain was removed because fluid production was minimal and fluid cytology revealed no intracellular or extracellular bacteria. Pseudomonas aeruginosa, Enterococcus spp., and a coagulase-positive Staphylococcus sp. (not S. aureus) grew from the aerobic and anaerobic cultures of the abdominal fluid. Each was susceptible to a combination of enrofloxacin and amoxicillin trihydrate/clavulanate potassium^u.

The dog was discharged 4 days following surgery. Enrofloxacin (6.1 mg/kg PO q 24 hr) and amoxicillin trihydrate/clavulanate potassium (16.9 mg/kg PO q 12 hr) were continued for 7 days. Tramadol^v (3.4 mg/kg PO q 8–12 hr) was given as needed for pain and discomfort for 7 days. No complications were noted and no further problems relating to the magnet ingestion were reported 1 yr following the surgical intervention.

Discussion

This case report describes a rare cause of gastrointestinal perforation and septic peritonitis in one dog. Ingestion of nonfood objects is common by small animals, particularly dogs and cats. The most common intestinal foreign bodies include bones, balls, toys, rocks, corncobs, cloth, metal (i.e., fish hooks and needles), peach pits, hairballs, tampons, and linear objects (i.e., string, pantyhose, ribbon, etc).² To the authors’ knowledge, this is the first report of magnet ingestion with subsequent bowel perforation leading to septic peritonitis in a dog. Until recently, magnet ingestion in the dog had not been reported in the veterinary literature.³

Magnet ingestion is infrequently reported in pediatric medicine, but typically affects children between the ages of 6 mo and 3 yr or adolescents imitating adults with body piercings.^4,5 Children who swallow multiple magnets are at risk for developing bowel perforation and peritonitis due to two magnets in adjacent bowel loops attracting each other and subsequently leading to pressure necrosis. Typically, the patient presents with bilious vomiting, and chronic abdominal pain.^4–8 Bowel obstruction, perforation, fistula formation, adhesions, intestinal volvulus, and death have all been reported in children after ingesting multiple magnets.^4,6–10 In 2006, these problems resulted in voluntary recalls of several children's toys with small magnetic components.⁶

When multiple magnets are ingested, there is a possibility of attraction across loops of bowel. A proposed mechanism of perforation involves continuous pressure on the bowel wall which exceeds the capillary perfusion pressure within the bowel wall leading to complete ischemia.¹¹After several hours of complete ischemia, the inflammatory infiltrate and the mucosal and submucosal hemorrhage and edema intensify.¹¹ Necrotic changes in the mucosa then lead to tissue breakdown and sloughing leading to ulcerations and exposed areas of submucosa. This process continues through the submucosa to the muscularis propria, resulting in perforation.

The case reported here was similar to the published pediatric case reports of magnet ingestion. One of the more common locations for perforations to occur in the reported pediatric cases was around the ileocecal valve.^4–6,8 In the dog described herein, the peritonitis involved the colon and the dog did not fulfill the criteria for sepsis or systemic inflammatory response syndrome.¹² This could be the result of the omental adhesions walling off peritoneal inflammation. Children older than 3 yr of age have a greater amount of fat throughout their omentum limiting peritoneal inflammation resulting in few abnormal physical examination findings.¹⁰

In the dog from this study, the radiographs showed the presence of metallic, radiopaque foreign objects and loss of abdominal detail. The severity of the damage, as well as the actual location of the magnets (embedded in the omentum), was not discernible from the radiographs. Given the patient's history and clinical signs, the most likely cause of these changes was the attraction of these magnets across bowel loops with subsequent pressure necrosis leading to perforation. Other potential differential diagnoses for the radiographic findings would depend on the radiopaque objects passing through the gastrointestinal tract or small bowel obstruction by the foreign objects. If the radiopaque foreign objects were not known to be magnets, further diagnostic evaluation could have been considered which would likely have included abdominal ultrasound and abdominocentesis with fluid cytology and analysis.

Conclusion

The ingestion of multiple magnets or magnets and metallic foreign objects should prompt quick intervention to prevent gastrointestinal damage from occurring.