Gastrointestinal ingestion of foreign bodies (FBs) is common in dogs (5,8). FBs can pass through the gastrointestinal tract without showing clinical signs or causing damage or can have a clinical impact, such as in cases of partial or complete obstruction (5,8). Common clinical signs associated with gastrointestinal FB ingestion include vomiting, abdominal pain, anorexia, absence of defecation, and diarrhea (5). Vomiting is the most common clinical sign of upper gastrointestinal obstruction, with symptoms commonly presenting 2-3 days after ingestion (5). The presence or absence of gastrointestinal obstruction may vary depending on the type of FB ingested; therefore, it is clinically important for the owner to be aware of instances of ingestion and the type of FB ingested (8).

Radiography is frequently used to assess small animals suspected to have gastrointestinal FBs (6,12). Radiopaque FBs may be easily identified; however, the radiographic findings that accompany mechanical obstruction of the small intestine can vary with the degree, duration, and location of the obstruction, and are usually non-specific (12). There are numerous other causes of gastrointestinal tract obstruction, including intussusception, neoplasia, adhesions, and strictures, all of which produce similar radiographic signs (12). Furthermore, the accuracy of the subjective assessment of abdominal radiographs to diagnose gastrointestinal mechanical obstruction has been reported to vary between 61% and 80.7-89.1% (6). If a FB is non-opaque or non-diagnostic on radiography, a gastrointestinal contrast study or ultrasonography may be used (1,6,9,12). However, gastrointestinal contrast studies are often not pursued because of the time-consuming nature of the procedure, which can delay the time to surgery, increase stress to the patient, is a contraindication in patients with concerns for gastrointestinal perforation (if barium is used as the contrast agent), and has the potential to be a non-diagnostic study if the patient vomits the contrast agent (6,9). Therefore, ultrasonography may be more useful for detecting non-opaque gastrointestinal FBs with greater accuracy in the diagnosis of mechanical obstruction (6,10,12).

On ultrasonographic examination, independent of the type of FB, the presence of a bright interface associated with acoustic shadowing is highly suggestive of a FB (11). However, depending on the physical properties of the FB, the ultrasonographic features may vary in size, shape, echogenicity, and acoustic shadowing (2,4,7,10,11). Although it may be difficult to diagnose gastrointestinal FBs with or without occult acoustic shadowing, segmental fluid or gas accumulation within the stomach or part of the intestinal tract can be used as an indicator of mechanical gastrointestinal obstruction (11).

In this report, we describe an unusual case of less-digestible pet food acting as an intestinal FB in a small-breed puppy, causing mechanical bowel obstruction.

A 6-month-old intact female Bichon Frise dog weighing 0.9 kg presented with vomiting, anorexia, and lethargy persisting for 3 days. According to the owner, the dog had no history of eating any foreign material, and all vaccinations were administered. A physical examination revealed no abnormalities, except for a body condition score of 2/5. A complete blood count revealed no abnormalities. Serum biochemistry findings showed elevated levels of alkaline phosphatase (ALP) (768 U/L; reference range, 47-254 U/L) and blood urea nitrogen (BUN) (49.6 mg/dL; reference range, 9.2-29.2 mg/dL). Tests for canine parvovirus, coronavirus, and Giardia yielded negative results. Abdominal radiography revealed moderate-to-severe gastric dilation with fluid, and mild gas dilation in some intestinal loops (Fig. 1). Radiographic findings suggested the possibility of mechanical obstruction or inflammation of the gastrointestinal tract.

Figure 1. Right lateral (A) and ventrodorsal (B) abdominal radiographs in this case show moderate-to-severe gastric dilation with fluid (arrowheads) and mildly gas-dilated intestinal loops (asterisks).

Abdominal ultrasonography was performed to further investigate the cause of gastrointestinal dilation, which revealed marked gastric dilation with a large amount of echogenic material, thought to be stagnant digested food, and dilation with fluid, mucus, and gas in the proximal duodenum, with decreased motility (Fig. 2). In addition, a rectangular, homogeneous, echogenic FB with no acoustic shadowing or comet tail sign was identified in the distal duodenal or jejunal lumen (Fig. 2). The small intestine distal to the FB showed a normal luminal size with decreased dilation. Considering the ultrasonographic characteristics of the FB in the present case, which exhibited a regular contour and shape with homogeneous echogenicity and non-shadowing, the differential diagnosis was considered as a type of pet food with hardness rather than general FBs. This finding led to re-consultation with the owner. The owner reported a history of administering dog gum 1 day before vomiting. Based on the ultrasonographic findings and history of eating dog gum, we considered the possibility that the FB in the small intestine was dog gum and immediately performed an enterotomy to improve the intestinal obstruction caused by this FB.

Figure 2. Abdominal ultrasonography reveals marked dilation with echogenic luminal contents of the stomach (A, asterisks) and dilation with fluid, mucus, and gas in the proximal duodenum with decreased motility (B). In addition, there is a rectangular, homogeneous echogenic foreign material (hash) with no acoustic shadowing or comet tail sign in the distal duodenal or jejunal lumen (C, D). The small intestine distal to the foreign material show a normal luminal size with decreased dilation (C).

During surgery, an FB was identified in the distal duodenal lumen causing dilation and congestion of the intestinal segment proximal to the FB (Fig. 3). Surgical removal of the FB was performed, and it was confirmed to be a less-digestible dog gum (Fig. 3). Postoperatively during hospitalization, the patient’s clinical signs were completely resolved with a return to normal appetite. The present case demonstrates that hard pet food, such as dog gum, can serve as an FB, causing mechanical bowel obstruction due to less-digestion in small-breed puppies, even without acoustic shadowing on ultrasound examination.

Figure 3. Gross appearance of the distal duodenum during surgery. The foreign body (asterisk) in the present case is evident in the distal duodenal lumen, causing dilation and congestion of the overall intestinal segment proximal to the foreign material (A). Surgical removal of the foreign material was performed and it was confirmed to be less-digestible dog gum (B).

This case represents an unusual case of less-digestible pet food acting as an intestinal FB in a small-breed puppy, causing mechanical intestinal obstruction. In the present case, suspicion of an intestinal FB arose considering the characteristics of both the radiography and ultrasonography findings, even though there was a lack of information obtained during the initial history-taking with the owner. In addition, the FB exhibited a regular shape with no acoustic shadowing on ultrasonography, indicating the possibility of food ingestion. This is clinically significant in that it differs from most FBs typically exhibiting partial or complete shadowing. Furthermore, the presence of a bright interface with strong shadowing enhances the certainty of the FB diagnosis (11). Although this FB exhibited no shadowing, it was not difficult to diagnose mechanical obstruction due to the intestinal FB. This was due to significant gastroduodenal dilation, reduced dilation of the intestinal loops distal to the FB, and a regular FB shape. Previously reported FBs with no shadowing in humans and veterinary medicine included small-sized grass awns or some plant awns, broken glass particles, and hair, although this observation was not consistent (2-4,10). The acoustic shadow may be either complete or partial depending on the angle of insonation and composition of the FB (4,10). This may also be determined by factors such as size, physical density, and the extent of degradation within the tissue, rather than by the type of FB (2,7). Therefore, in this case, the FB may have developed shadowing on ultrasonography over time.

The authors investigated the ultrasonographic characteristics of five different dog chews according to their hardness. In their intact state, all types showed a similar appearance on ultrasonography, exhibiting a hyperechoic interface with strong shadowing. However, to mimic the digested state, ultrasonography was performed after storing them in warm water for about 16 hours. The bone-shaped, non-flexible dog gum type, which had the highest hardness, was accompanied by strong shadowing. All other four flexible types of dog chew showed variable echogenic textures without shadowing (Fig. 4). Two of these types were characterized by the presence of hyperechoic internal structures due to specific ingredients (Fig. 4). The five types of dog chews exhibited varying ultrasonographic appearances of internal echotexture as well as the presence or absence of acoustic shadowing. The dog chew in the present patient showed the most similar characteristics to types B and D in Figure 4.

Figure 4. Ultrasonographic characteristics of five different dog chews according to their hardness. From A to E, hardness weakens and flexibility increases. To mimic the digested state, ultrasonography was performed after storing the chews in warm water for about 16 hours. The bone-shaped, non-flexible dog gum type (A), which had the highest hardness, is accompanied by strong shadowing. On the other hand, all other four flexible types of dog chews (B-E) show variable echogenic textures without shadowing. Type C and E are characterized by the presence of hyperechoic internal structures due to specific ingredients. The five types of dog chews present varying ultrasonographic appearances of internal echotexture as well as the presence or absence of acoustic shadowing.

In a retrospective study that analyzed gastrointestinal FBs in 72 dogs, various FB types were reported, including kid toys, metallic objects, cloth, plastic materials, peach stones, fishhooks, and plant materials (5). However, no cases of gastrointestinal obstruction caused by the ingestion of pet food have been reported. Another retrospective study involving 208 cases reported that owners’ awareness of their pets’ FB ingestion was clinically important for early treatment and successful recovery (8). Therefore, in this case, obtaining a history of dog gum ingestion through a re-take of the history with the owner after the ultrasound examination was significantly important. Even if this information had not been obtained from the owner, we would have considered surgical removal. However, based on the owner's information, a rapid surgical approach could be pursued with greater confidence. We believe that a prompt surgical decision could have facilitated enterotomy rather than enterectomy with anastomosis. This is because prolonged intestinal obstruction caused by a FB may lead to various complications necessitating intestinal anastomosis, and postoperative recovery and prognosis may become challenging (5,8).

We frequently encounter cases in which foods with a hard texture, such as dog gum, are lodged in the throat or esophagus, leading to esophageal dilation or increased soft-tissue opacity in the esophagus on radiography. However, it is rare for less-digestible food, as in this patient's case, to progress to the small intestine, resulting in mechanical bowel obstruction.

About two months postoperatively, the patient underwent magnetic resonance imaging and computed tomography scans for neck pain sign, and was diagnosed with AAI with occipital dysplasia and no abnormalities in the abdominal organs. At that time, a blood test showed that the ALP level was reduced to 447 U/L and the BUN level was reduced to 25.3 mg/dL. Therefore, at the time of intestinal operation, the authors thought that the increased ALP level could be associated with the young age and the increased BUN level could be associated with enteritis caused by intestinal obstruction.

This study has some limitations in definitively characterizing the ultrasonographic features of various digestible hard pet foods, as well as challenges in evaluating the incidence of mechanical intestinal obstruction caused by these pet foods, particularly in young or small-sized dogs.

This case describes the importance of performing concurrent radiographic and ultrasonographic examinations in companion animals presenting with gastrointestinal symptoms, even when the owner’s initial history may be insufficient. This highlights the crucial role of these diagnostic imaging modalities in the diagnosis of intestinal obstruction caused by FBs. Additionally, this case underscores the potential challenges associated with the digestibility of solid foods, such as dog gum, in small animals. When the size of these materials is considerable, intestinal obstruction may occur, necessitating surgical removal. Based on this case study, veterinary clinicians in first-opinion practice should take the opportunity to educate owners of low-weight, young, small-breed dogs about the risks and precautions associated with the ingestion of hard food items, such as dog chews.

This report describes an unusual case of a less-digestible hard pet food acting as an intestinal FB in a small-breed puppy, causing mechanical intestinal obstruction. This case may be helpful in educating veterinarians and owners in first-opinion practice to take precautions when feeding hard pet food.

None.

The authors have no conflicting interests.