The Use of Ultrasound to Diagnose Intestinal Foreign Bodies
The Use of Ultrasound to Diagnose Intestinal Foreign Bodies
Jeff Johansson, DVM – January 2012
Gastrointestinal foreign bodies in dogs and cats can be challenging diagnoses for veterinary clinicians. Along with pertinent physical exam findings and patient history, veterinarians often rely on laboratory tests and abdominal imaging (radiographs, contrast studies, and/or ultrasonography) to support a diagnosis of foreign body/ obstruction (FBO). Radiography, including plain films as well as contrast studies, has long been the imaging means of choice for diagnosing intestinal foreign bodies/ obstruction, due to widespread availability of equipment and extensive experience and familiarity among veterinarians in interpreting radiographs.
With the increasing availability of ultrasonography, veterinarians now have an additional tool in evaluating patients with suspected FBO, in some cases providing a diagnosis where radiographs may be unsupportive or equivocal. A recent study in Veterinary Radiology & Ultrasound (May 2011) of 27 dogs with FBO in a sample population of 82 dogs showed that ultrasound was able to definitively diagnose or rule out small-intestinal FBO in 97% of cases, compared to radiography which was definitive in 70% of cases. Another study of 16 animals with confirmed FBO showed that radiography detected foreign bodies in 9 animals, while ultrasonography detected a foreign body in all 16 animals. Ultrasounds can be completed within 30 minutes (versus a barium study which may take hours), and allows the evaluation of peristalsis, as well as evaluation of other abdominal organs. Together, survey radiography and ultrasonography provide an excellent means of detecting intestinal FBO.
Ultrasonographic signs consistent with FBO include segmental small intestinal dilation, thickening of the gastrointestinal wall with loss of layering, plication of the bowel wall (in cases of linear FBO), as well as actual visualization of a foreign body or acoustic shadowing effect, which occurs at the interface of the object with the bowel wall. Of course other conditions can be mistaken for FBO. Gas and feces in the colon will often produce a shadowing effect, which could be mistaken for a foreign body. Due to the extensive length of the jejunum in small animals, a thorough examination of the entire GI tract is needed so as not to miss a potential lesion, and this of course requires experience, patience, and time on behalf of the ultrasonographer to perform a complete examination.
At REACH of Asheville, we have been using ultrasonography as a complementary tool in working up patients with a variety of abdominal diseases, including intestinal FBO. Oftentimes, we will perform a sonogram in conjunction with radiographs in working up cases of suspected FBO. Recently, we have had several cases where ultrasound was able to make a diagnosis where radiographs may have been equivocal.
CASE 1: “Lucy” (6 months; FI Boxer)
Lucy presented with a two week history of intermittent vomiting and progressive weight loss. On physical exam, she was slightly tachycardic (HR 156), but temperature, respiration, and hydration were within normal limits. She was tense on abdominal palpation, and a loop of thickened small intestine was palpable. She was sedated for an ultrasound which showed an irregular, curvilinear object in the duodenum which displayed strong shadow casting (FIGURE 1). The stomach and remainder of the small intestine appeared empty. Based on suggestive history, exam findings, and ultrasonographic evidence, Lucy was taken to surgery, where an enterotomy was performed, and an intact pair of women’s underwear was removed from the duodenum. Surgery went well, and Lucy was transferred to her regular veterinarian the next day for further care.
Figure 1- note the shadowing effect on the small intestine at the left side of the image at the site of the foreign body. Distal to this, the small intestine appears narrowed.
CASE 2: “Hagrid” (7y MN Newfoundland)
Hagrid presented with a 5 day history of lethargy, acting nauseous, and intermittent vomiting. On physical exam, he was mildly dehydrated, rectal temperature was 101.9F, HR was 124, and RR was slightly elevated at 60. Lungs were clear, and no murmur was ausculted. He was painful on palpation of the mid-abdomen, but it was difficult to determine the source of his pain. Radiographs showed several areas of gas-filled small intestine, with segmental dilation of a loop of small intestine (FIGURE 2). Hagrid was sedated, and an abdominal ultrasound showed evidence of pneumoperiotoneum, scant abdominal fluid, and a segment of bowel with significant loss of layering, as well as a possible linear object within the lumen, which appeared to penetrate through the abdominal wall (FIGURE 3). The segment appeared to be surrounded by a diffuse, hyperechoic structure. Abdominocentesis revealed large numbers of erythrocytes and granulocytes with no bacteria appreciated. An exploratory laparotomy was performed and a hard plastic foreign body (8cm) was found in the ileum. The object had perforated through the wall of the ileum and the surrounding intestine was discolored. The greater omentum was found to have partially sealed the perforation, but there was some spillage of intestinal contents into the abdomen. A resection and anastomosis were performed, the abdomen was lavaged, and Hagrid was managed post-operatively with broad spectrum antibiotics, IV fluids, opioid pain medication, and an H2 antagonist. He recovered well through the night and was transferred to his family veterinarian for further care.
FIGURE 2. This lateral abdominal radiograph shows dilated loops of small intestine, gas and fecal material in the colon, decreased abdominal serosal detail, and gas in the stomach.
Figure 3. A hyperechoic linear structure is shown protruding through the bowel wall, and there is a hyperechoic density surrounding the structure, which is the greater omentum found at the site of perforation during surgery
While ultrasound was not the sole determinant in these cases as to whether surgical intervention was indicated, it served as an adjunctive diagnostic means that ultimately led to prompt diagnosis and treatment of these cases of intestinal FBO. In case #2 we were able to determine a possible perforation with peritonitis and recommend prompt surgical treatment.
At REACH of Asheville, we are pleased to offer ultrasound services to our clients, patients, and the veterinary community of Western North Carolina so that we may provide excellent patient care. In addition to our emergency services, we offer referral ultrasounds by appointment, and work via telemedicine with board-certified radiologists, so that we may provide an excellent level of care.
Veterinary Radiology and Ultrasound, 2011 May-Jun; 52(3):248-55
Veterinary Radiology and Ultrasound, 2006 Jul-Aug;47(4):404:8