Under ultrasound observation, Hashimoto's thyroiditis generally presents as a diffuse enlargement of the thyroid, often symmetrically, although there are cases of unilateral enlargement as well. Additionally, the surface of the thyroid appears irregular and nodular. The ultrasound often reveals uneven echogenicity in the gland, sometimes with nodular changes and unclear boundaries. However, the ultrasonographic characteristics of Hashimoto's thyroiditis are not particularly specific unless it's a typical case of the disease, which can be roughly diagnosed via ultrasound. For atypical or early cases of Hashimoto's thyroiditis, diagnosis typically requires thyroid function tests, known as the "thyroid function six-item test," which remains the gold standard for diagnosing Hashimoto's thyroiditis.