Two Common Pitfalls of Abdominal Radiographs in Dogs and Cats
The following are two findings on abdominal radiographs that I see commonly misdiagnosed in dogs and cats. Below are two tips that may help you interpret x-rays in your veterinary patients.
Tip #1. Be Careful Not to Mistake the Pylorus as Soft Tissue Mass
On a right lateral abdominal radiograph, the pylorus of the stomach (being on the right of midline) is dependent and is usually either empty or the mobile contents fall into and fill the pylorus. This causes summation of the wall, if empty, or with the contents (such as mild fluid). On many right lateral images this can cause a well-defined soft tissue opacity, caudal or caudoventral to the liver, mimicking a true soft tissue mass.
Here is an example (Figure 1 and Figure 2):
Figure 1. Right lateral abdominal radiograph of a cat. Please note the round soft tissue opacity that was falsely interpreted as a hepatic mass (black arrows).
Figure 2. Left lateral abdominal radiograph of the same cat. Please note the gas-filled nondependent pylorus is now visualized with normal intraluminal gas highlighting the wall (black arrows).
The left lateral image shifts the gas from the fundus (on the right lateral image) to the pylorus, commonly filling the lumen. The left lateral abdominal radiograph is pertinent in confirming that the soft tissue mass effect is the normal pylorus. The left lateral image can also shift gas into the duodenum and can be very useful in the diagnosing linear foreign bodies and pyloric outflow obstructions. Only using a right lateral radiograph can create the artifactual mass effect and obscure visibility of a foreign object in the pylorus.
Tip #2. Determine Gastric Ingesta from Foreign Material
Quite commonly a dog or cat presents with possible foreign body ingestion or inappetence, with or without, an episode of vomiting. Radiographs are performed and soft tissue material is present within the stomach, whether it’s thoracic or abdominal radiographs. Is the opacity in the stomach postprandial gastric ingesta or foreign material?
The material is in the fundus and the small intestines are unremarkable, so obstruction is not likely. What do you do? What is the best and most efficient way to figure it out?
- Surgery/Endoscopy
- Ultrasound
- Radiographs
Answer:
Radiographs. Gastric ingesta and soft tissue opaque foreign material can look identical on radiographs, so there is not enough information to perform endoscopy. If the patient is guaranteed to not have eaten in days, then the likelihood for foreign material is high. However, too many times we will repeat abdominal radiographs, with or without concurrent supportive care, and the material is resolved. Similar to radiographs, ultrasound is poor at differentiating ingesta from foreign material. Ultrasound can rule out intestinal obstruction, however many times nonobstructive gastric foreign material will appear identical to foreign material. So, sending this patient for endoscopy or ultrasound is not the next diagnostic step when trying to differentiate gastric ingesta from soft tissue foreign material.
Gastric emptying time in dogs can be up to 17 hours, so repeating radiographs at the end of the day (i.e. six hours later) will likely not be enough time to confidently discern gastric foreign material from ingesta. Many times, these recheck radiographs are performed too early and the remaining contents can easily be ingesta.
I recommend keeping the patient nil per os (NPO) for 12-24 hours and repeating three-view abdominal radiographs the next day.
Below are two cases to demonstrate this tip.
Case A. Here is a typical case: A three-year-old dog presents with a one-day history of anorexia with one episode of vomiting. Radiographs are taken to evaluate this dog for a foreign body (See Figures 3 and 4).
Figure 3. Ventrodorsal abdominal radiograph of a dog. Please see the black arrows that define the outer wall of the stomach.
Figure 4. Right lateral abdominal radiograph of a dog. Note the moderate to marked amount of heterogenous soft tissue material within the fundus of the stomach.
The patient was hospitalized overnight and did well with no vomiting. Repeat abdominal radiographs (Figures 5 and 6) were taken the next morning approximately 14 hours after the radiographs taken in Figures 3 and 4. The stomach is now empty (mildly gas-filled) and the small intestines are normal. Patient went home and did well.
Figure 5. Right lateral radiograph of a dog taken as a recheck the next day (14 hours after Figures 3 and 4).
Figure 6. Ventrodorsal radiograph of a dog taken the next day (14 hours) after those in Figure 3 and 4. Please see the black arrows outlining the empty stomach (mildly gas-filled) and the small intestines are normal.
Case B. Here is another similar case that looked more suspicious for foreign material. This case is of another dog that presented for vomiting. Abdominal radiographs were taken (Figures 7 and 8).
Figure 7. Right lateral radiograph of a dog with a two-day history of vomiting. Black arrows define margins of suspected foreign material.
Figure 8. Ventrodorsal abdominal radiograph of a dog with two-day history of vomiting. Black arrows define margins of suspected foreign material.
The ventrodorsal abdominal radiograph identifies a round soft tissue opacity in the deep part of the fundus of the stomach (concerning for foreign material, gastric mass, or ingesta). A left lateral ruled out linear foreign body anchored, or extending into, the pylorus.
The dog was hospitalized, and radiographs were repeated 14 hours later (Figure 9 and 10)
Figure 9. Right lateral radiograph of a dog with a two-day history of vomiting taken 14 hours after the radiograph identified in Figure 7. Black arrows define the outer wall of the stomach.
Figure 10. Ventrodorsal abdominal radiograph of a dog with a two-day history of vomiting taken 14 hours after the radiograph identified in Figure 8. Black arrows define the outer wall of the stomach. The stomach is empty with a small amount of air.
This case demonstrates the completely resolved gastric material. As you can see soft tissue ingesta in the stomach can mimic foreign material. The history of vomiting or inappetence with gastric material raises the concern for foreign material, and should be investigated, but does not confirm it. If the material in these cases had been persistent, foreign material would be highly likely. Recheck radiographs with enough time lapsed is very useful for determining gastric ingesta from foreign material. The radiographic findings should also be correlated clinically with how the patient responded to supportive care.
Hopefully these tips can be helpful as guidelines of how to proceed when these are presented to you in your veterinary patients.
