Systematic thoracic ultrasonography in acute bovine respiratory disease of feedlot steers: impact of lung consolidation on diagnosis and prognosis in a case-control study

A study was conducted to evaluate the diagnostic and prognostic value of thoracic ultrasonography (TUS) in feedlot calves with clinical signs attributable to bovine respiratory disease (BRD). Twenty-nine BRD cases and 15 asymptomatic controls were evaluated using systematic TUS on the day of initial pull (day 0), and days 3, 6, 9, and 15. Four-second ultrasound loops were saved at 46 locations per animal and later evaluated off-line for evidence of lung pathology. Five TUS indicators of lung lesions and 4 indices of consolidation were evaluated for ability to differentiate between healthy controls and BRD cases, as well as predict death (negative outcome) among non-treated BRD cases. The number of sites with consolidation (SITES), number of sites with pleural irregularities (PIRR), maximal depth of consolidation (DEPTH), maximal area of consolidation (AREA), and total consolidated area (TCA) were found to be significantly higher in BRD cases than controls at enrollment (P<0.05). These same parameters (SITES, PIRR, DEPTH, AREA, TCA) were found to be significantly higher at enrollment for BRD cases that died before the end of the 15-day observation period (P<0.05). Among BRD cases, 9 of 46 sites examined had an odds ratio of negative outcome significantly greater than 1 when consolidation was present at enrollment (P<0.05). This study demonstrates that TUS may prove useful in feedlot cattle for determining the extent of lung lesions and predict outcome in BRD cases.