Echo-Doppler findings of a carotid-jugular fistula in a foal.

This study documents the case of a seven-month-old foal who was diagnosed with a carotid-jugular fistula, an abnormal connection between the jugular vein and carotid artery, revealed by symptoms such as dilated veins and abnormal blood flow patterns detected via Doppler imaging.

Case Background

• The seven-month-old male Standardbred examined in this study was referred due to a four-month history of distension, or swelling, seen in the left jugular groove.
• During physical examination, severely dilated left maxillary, linguofacial, and jugular veins were noted. These are veins located around the horse’s mouth, face, and neck respectively.

Diagnostic Techniques

• Blood gas analysis was performed, which indicated a higher level of oxygenation in the left jugular vein compared to what is typically expected.
• Doppler imaging techniques, including pulsed-wave Doppler interrogation and color flow mapping, were utilized to examine the left jugular blood flow. These techniques use ultrasound technology to visualize the speed and direction of blood flow in the veins.
• These techniques revealed unusual bidirectional flow signals, with normal systolic (when the heart is contracting) and early diastolic (when the heart is relaxing) flow, contrasted with abnormal late diastolic retrograde (backward) flow.

Findings and Diagnosis

• A systolic-diastolic signal with spectral broadening, indicating variation in the velocity of blood flow, was detected in the distal left cervical region when the sample gate, or measurement area, was positioned near the wall of the internal jugular vein.
• Color Doppler imaging revealed blood flow passage between the left common carotid artery (supplying blood to the brain and neck) and the left jugular vein (carrying deoxygenated blood from the head back to the heart) through a small carotid-jugular fistula. This is an abnormal connection between these two blood vessels that should not normally exist, indicating a congenital defect or an injury.
• Notably elevated blood flow velocities and volumetric flow (the volume of blood flowing per unit of time), along with a reduced resistive index (indicating reduced resistance to blood flow), were recorded in the left common carotid artery compared to the right one.