Changes in measurable ultrasonographic parameters in growing Arabian foals from birth to 1 year.

Background: Utrasonographic measurements of the abdominal viscera and the heart in growing Arabian foals have not been described.

Objectives: To establish normal intervals for ultrasonographic measurements of cardiac indices and abdominal viscera in growing Arabian foals from birth to 1 year of age.

Study design: Prospective longitudinal descriptive study.

Methods: Ultrasonographic images were captured from 15 foals every 3 months from 1 week to 1 year of age. During each examination, at least three images were obtained at each location and measurements were obtained using standardised ultrasonographic approaches. Reference intervals were established for 11 indices of abdominal viscera (left and right kidney length, width and cortical thickness; left and right caudal aorta diameter, caecal wall thickness and vasculature diameter; and stomach wall thickness) and 11 cardiac indices (pulmonary artery diameter at end-diastole, aortic diameter at end-diastole, left atrial diameter at end-diastole, right ventricular internal diameter at end-diastole, interventricular septal thickness at end-diastole, interventricular septal thickness at peak-systole, left ventricular internal diameter at end-diastole, left ventricular internal diameter at peak-systole, left ventricular free wall thickness at end-diastole, left ventricular free wall thickness at peak-systole and fractional shortening).

Results: All abdominal structures grew in size from the first week of life up to 1 year of age. All cardiac variables, except for interventricular septal thickness at end-diastole and fractional shortening, increased with age up to 1 year. No sex differences were detected.

Main limitations: Small sample size.

Conclusions: This study provides age-appropriate reference intervals for several ultrasonographically visible structures in Arabian foals up to 1 year of age. This information is essential for clinical management and decision-making in this sub-population of equine patients.