Which structure is indicated by the arrow on this image?

The ultrasound image shows a transverse view of the lower neck region at the thyroid level. The arrow is pointing to a round-to-oval structure located posterior and slightly to the left of the thyroid gland. The structure has a characteristic "target" or "bull's-eye" appearance with a hypoechoic outer ring and echogenic central mucosal interface — this is classic for the esophagus when seen in transverse view.

Key sonographic features of the esophagus:

It lies posterior to the left lobe of the thyroid.

It demonstrates a layered wall structure ("target" or "bull's-eye" appearance).

It may change shape or move during swallowing, and occasionally air bubbles or movement of fluid may be observed.

Comparison of answer choices:

A. Parathyroid glands are small, homogeneous, hypoechoic, and located posterior to the thyroid — but do not have this layered target appearance.

B. Lymph nodes have a hypoechoic cortex and echogenic hilum and are typically oval or bean-shaped, without the concentric ring appearance.

C. Esophagus — Correct. The location, appearance, and structure are consistent with the cervical esophagus.

D. Paragangliomas are highly vascular and more commonly located in the carotid body or adrenal region, not in this location or with this sonographic pattern.