Development and application of a focused ultrasound protocol in neonatal foals.

Abstract: This study aimed to develop a standardized ultrasound (US) protocol using selected thoracic and abdominal acoustic windows, to assess its feasibility and applicability in healthy foals, and to evaluate its usefulness for detecting common thoracic and abdominal conditions in sick foals. The Focused US (FUS) protocol included 12 thoraco-abdominal windows (4 right-side, 3 ventral, 5 left-side) using a curved-array probe. It was applied to cohorts of healthy (n = 17) and sick (n = 23) foals by a veterinary clinician with limited US experience. The FUS showed good feasibility and applicability, with clear visualization of target abdominal structures. Diagnostic usefulness was high for identifying gastrointestinal disease and peritoneal effusions. However, several challenges emerged: the need to change recumbency, the relatively large number of US windows, the need for staff to restrain foals, and the prioritization of other diagnostic or therapeutic procedures in sick foals. A shortened Foal Oriented Compressed US (FOCUS) protocol was developed, including 7 thoraco-abdominal windows from a single right recumbency (4 right-side, 3 ventral), and was tested in healthy (n = 3) and sick (n = 3) foals by three clinicians with varying levels of experience. The FOCUS proved significantly faster than FUS, with a short acquisition time (median 7 min, range 3-10 min). Main limitations include single-operator image acquisition, the small cohort of sick foals assessed using FUS, and limited evaluation of the FOCUS protocol. In conclusion, FUS can be performed by veterinarians without extensive US experience. However, in emergency settings, FOCUS may be preferred due to its greater time efficiency.