**5. Echocardiography**

Ultrasonography is currently recognized as the preferred diagnostic method for investigating cardiac abnormalities, including pericardial effusion in cattle [11].

Echocardiography is non-invasive and can be performed on the standing and compliant animal on site [5]. This does not include evaluation via Doppler due to higher expense and problems with accessibility in farm practice. When carrying out an echocardiographic assessment it has been recommended that a 3–3.5 MHz transducer is used observing caudal long, caudal short and cranial long axis views on the right side and caudal long and cranial long axis views on the left side [23, 24].

Common signs noted within the literature relating to thoracic ultrasonography and echocardiography in TP cases include displacement of the heart away from the thoracic wall, increased echogenicity of the heart, generalized thickening of the pericardium and the presence of a hypoechoic fluid exudate between the parietal and visceral pericardium, which often contains echogenic fibrin deposits [6, 25]. As a result of fluid accumulation in the pericardium, causing a subsequent cardiac tamponade, compression of ventricles and reduced ventricular motility can also be observed [11, 26–28]. The ultrasonographic findings described provide strong evidence for the diagnosis of pericarditis.

Factors to consider when using echocardiogram include the training experience of the clinician, the views obtained and the restraint and position of the cow. To ensure a full and complete assessment, ultrasound images should also be obtained from the lung fields, mediastinum pleural space and abdominal region, extending the scan from the 3rd intercostal space to the 12th [15]. It has been suggested that a productive and conclusive echocardiogram would take 20 minutes to perform in a farm setting [29]. Studies have also highlighted the importance of assessing the reticulum in retrospect to the diaphragm in order to interpret signs of abscess formation, adhesions and peritonitis, which may occur alongside TP [21]. This subsequently adds additional time to the scanning session but is performed at the farmer's request. In a study of 51 healthy cattle, it was shown that differences in cattle temperament, body condition score and rib width can result in a lack of consistency between thoracic ultrasonography assessments [26]. This further emphasises the importance of clinician experience when producing echocardiograms in cattle, alongside good anatomical comprehension to prevent over interpretation.
