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.
References:
Rumack CM, Wilson SR, Charboneau JW, Levine D. Diagnostic Ultrasound, 5th ed. Elsevier; 2017.
Grant EG, Tessler FN, Hoang JK, et al. Thyroid Ultrasound Reporting Lexicon: White Paper of the ACR TI- RADS Committee. J Am Coll Radiol. 2015.
Hagen-Ansert SL. Textbook of Diagnostic Sonography, 8th ed. Elsevier; 2017.