From the Guidelines
A hypo-echoic texture on an ultrasound image indicates that the tissue or structure appears darker than surrounding tissues because it reflects fewer sound waves back to the ultrasound probe, suggesting the presence of fluid or higher cellular density. This appearance is commonly associated with various types of lesions, tumors, cysts with internal components, inflammation, or edema, as seen in studies such as 1 which shows a hemorrhagic cyst with hypoechoic debris. The physical explanation for this phenomenon relates to the acoustic impedance of the tissue, where tissues with similar acoustic properties to water tend to absorb more sound waves rather than reflecting them back to the transducer, resulting in the darker appearance 1.
When interpreting hypo-echoic findings, it's crucial to consider them in clinical context, as they are not specific to any single condition but rather represent a physical property that can be present in various normal and abnormal tissues. For instance, many solid tumors appear hypo-echoic, as do areas of inflammation or infection, and differentiation between malignant and benign lesions is not always possible with B-mode US alone 1.
Some studies suggest specific patterns for certain conditions, such as seminoma germ cell tumors often being more homogeneously hypoechoic, whereas nonseminomatous germ cell tumors are often nonhomogenously hypoechoic due to areas of calcification and/or necrosis 1. However, the general consensus is that a sonographic detection of a solid or mixed cystic lesion mass requires additional imaging or surgical exploration.
Given the variety of conditions that can present with hypo-echoic textures on ultrasound, clinical correlation and further diagnostic evaluation are essential for accurate diagnosis and management, emphasizing the importance of considering the clinical context and potentially pursuing additional imaging or tissue diagnosis to improve accuracy, as highlighted in studies such as 1 and 1.
From the Research
Definition of Hypo-echoic Texture
A hypo-echoic texture on an ultrasound image refers to an area that appears darker than the surrounding tissue, indicating lower echogenicity. This means that the area reflects fewer ultrasound waves back to the transducer, resulting in a lower intensity signal.
Causes of Hypo-echoic Texture
- Fat in certain anatomic locations can appear hypo-echoic on ultrasound images, as seen in studies of hypoechoic fat in and around the kidneys and in ovarian neoplasms 2.
- Focal hypoechogenicity within a "bright" liver can be caused by areas with fewer lipid droplets, resulting in a hypo-echoic appearance 3.
- Hypo-echoic areas on ultrasound images of atheroma are not always diagnostic of fatty plaque, as fibrous tissue in atherosclerotic plaques can also appear hypo-echoic depending on collagen fiber morphology 4.
- In the prostate, hypo-echoic areas can be caused by variations in sound speed of prostate tissue components, but echo intensity does not reliably distinguish between cancerous and non-cancerous tissue 5.
Clinical Significance
- Hypo-echoic texture can be associated with various conditions, including prostatitis, which exhibits a homogeneous echo pattern and is hypoechoic 6.
- Focal areas of increased or decreased echogenicity with irregular margins can be characteristic of prostatic carcinoma 6.
- Understanding the causes of hypo-echoic texture is important for accurate interpretation of ultrasound images and diagnosis of underlying conditions 2, 3, 4, 5, 6.