A sick calf comes into the chute with obvious respiratory disease. The question isn’t whether it is sick. The question is how much lung damage is present and what that means for the next decision.
That is the premise behind targeted thoracic ultrasound (TUS) developed by Dr. Luis Feitoza, director of animal health and research at Innovative Livestock Services and adjunct faculty at Kansas State University.
A systematic thoracic ultrasound examination can take several minutes and, including handling, considerably longer. Feitoza’s targeted approach focuses on a smaller portion of the lung and can be completed in about 60 to 90 seconds.
“We are not worried about diagnosing the disease,” Feitoza says. “Our intention here is to see how developed the disease is.”
Getting Started
Feitoza’s research provides a straightforward framework for veterinarians interested in incorporating targeted TUS into BRD evaluations.
Equipment: Use a linear or convex probe operating at approximately 3.5-5 MHz. Lower frequencies provide the penetration needed for adult cattle.
Coupling: Spray 70% isopropyl alcohol on the skin. Clipping or shaving isn’t necessary when cattle are reasonably clean.
Side and location: Feitoza’s targeted research protocol evaluates the right caudodorsal lung field, with some assessment of the middle lung field.
Probe position: Hold the probe parallel to the ribs. Fan the probe within the intercostal space to examine a larger area without repeatedly repositioning it.
Time: Once proficient, the target is approximately 60-90 seconds per animal.
The goal is not to replace a complete thoracic examination. It is to collect a standardized set of observations quickly enough to fit into a normal chute-side workflow.
Look for Three Things
Start by identifying the pleural line. In a normal aerated lung, it should be smooth, bright and move with respiration. Repeated horizontal A-lines beneath it are normal and reflect the air-filled lung.
Then look for:
B-lines: Vertical artifacts extending from the pleural line toward the bottom of the screen indicate loss of aeration. Feitoza’s research uses three or more B-lines in an image as an important abnormal finding. Wider B-lines indicate more extensive involvement.
Pleural abnormalities: A normal pleural line is smooth. A “moth-eaten” appearance, with irregular areas along the pleural surface, is associated with more severe disease and poorer outcomes.
Consolidation: At the most severe end of the ultrasound lung score, normal aerated lung is replaced by tissue-like areas that can resemble the liver. This finding is particularly useful when trying to distinguish pneumonia patterns.
Use Consolidation to Differentiate Pneumonia
The targeted scan can provide more than a severity assessment.
Feitoza’s research compared ultrasound findings with histopathology and found that consolidation strongly favored bronchopneumonia (BP) over interstitial pneumonia (IP). Intermediate lung scores without consolidation were more frequently associated with IP, while severe consolidation was much more consistent with BP.
“Interstitial pneumonia doesn’t have consolidation,” Feitoza says. “When we do see that, we can basically rule out interstitial pneumonia and basically make the call that is bronchopneumonia.”
He describes suspected interstitial disease as a more diffuse, bright or “washed-out” appearance, while BP tends to produce more localized lesions and consolidation.
Use the Scan to Assess Prognosis
The other major application is risk stratification.
At first BRD treatment, higher ultrasound lung scores were associated with greater probability of treatment failure. In one study, the predicted probability of first-treatment failure increased from 0.32 at a lung score of 1 to 0.74 at a score of 5. Three or more B-lines and a moth-eaten sign were also associated with increased treatment-failure risk.
The findings were even more pronounced in cattle with repeated BRD treatments. At the third or later treatment, cattle with three or more B-lines had an 84% probability of disease-not-finished within 60 days, compared with 34% for cattle with 0-2 B-lines. A moth-eaten sign was associated with a 78% probability of DNF versus 43% when it was absent.
For Feitoza, those findings can change management.
“If that animal has a lung score of 4 or 5, that animal is not getting treatment. It will be culled,” he says of cattle that have already received multiple treatments. For an animal at first treatment, he takes a more conservative approach, potentially keeping cattle with concerning lung findings closer to the hospital for reassessment.
The ultrasound result isn’t a stand-alone treatment decision. It adds another objective measure to the clinical signs, treatment history and other information already available to the veterinarian.
Train for Repetition
Targeted TUS does not have to be performed exclusively by veterinarians.
Feitoza trains feedyard personnel by first demonstrating the technique on about 5-10 animals, then watching the trainee perform the scan and correcting probe placement and interpretation.
“There is not a number,” he says about how long training should take. “It’s about repetitions.”
An experienced cattle handler may become proficient in a morning with enough repetitions, while someone completely new to ultrasound may need several days. Remote image review can provide continued veterinary oversight after initial training.
For veterinarians looking for another way to evaluate BRD cases, that may be the biggest advantage of targeted TUS: it doesn’t require a perfect ultrasound examination. It requires a consistent, fast examination that answers a useful question.
To hear more from Dr. Feitoza about thoracic ultrasound, as well as other veterinarians who presented their work at the American Association of Bovine Practitioners annual conference, check out the latest episode of ‘The Bovine Vet Podcast’:
