Tonight we looked at 2-3 minute ultrasound videos as preparation for the board exams. No matter how many ultrasounds you’ve done, it’s disconcerting to watch a partial scan that someone else has performed. They will be scanning with a different speed and pattern than you would, and the image may not follow the anatomy you would like to evaluate. In addition, some scans will be from the lateral position, and some from dorsal. Practicing reading these short loops is helpful for the oral boards.
One of the cases we discussed was a 4 month old mixed breed dog who had gotten into some wood preservative a few days earlier. He presented for vomiting and diarrhea. The ultrasound scan showed multiple fluid-distended loops of small intestine. Some loops contained parallel echogenic lines which were ascarids. At least one loop tapered to more normal appearing small intestine. The colon was also filled with fluid, and there were enlarged, hypoechoic mesenteric lymph nodes and a small amount of peritoneal effusion.
Differential diagnoses for these dilated bowel loops included viral or toxic enteritis, or a mechanical obstruction. The ascarids were likely an incidental finding. Lymphadenopathy could be partly due to the animal’s age, or be reactive to an inflammatory process. The small amount of fluid seen in the peritoneum was likely because of the young age.
Since the ultrasound scan was only about 2 minutes long, and certainly didn’t cover the entire abdomen, the question was what to recommend as a next step. Although there was no evidence of obstruction on the video, we never saw the ileocolic junction, nor did we see the entire small intestine. We also did not see the dilated bowel followed to both ends to see if it tapered to normal or ended in an obstruction.
Given that the findings could indicate obstruction or enteritis, the consensus was to state that there was no evidence of obstruction on this video, but there was not enough information to rule it out. Pathology like intermittent intessusception or a small foreign body at the ileocolic junction could still be present. Appropriate next steps would be to suggest investigating these areas with ultrasound, survey radiographs to evaluate the pattern of bowel dilation, and an upper GI to confirm patency of the small intestine. If the survey radiographs showed a distal obstructive pattern, a barium enema or pneumocolon could also be useful. This case was diagnosed as parvovirus, which can commonly present with severely dilated small intestine that mimics obstruction.
The take-home message was to evaluate what you have seen, and also to consider what you have not seen and ruled out. Additional imaging is always appropriate when you are suspicious of diseases that could be missed given the information you have at hand.
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