What is the ultrasonographic (US) appearance of a cyst?

From the Guidelines

Cysts on ultrasound (US) typically appear as well-defined, round or oval structures with smooth borders and anechoic (black) interiors due to their fluid content, as described in the most recent and highest quality study by 1. The ultrasonographic appearance of a cyst is characterized by several key features, including:

• A well-defined, round or oval shape with smooth borders
• An anechoic (black) interior due to the fluid content
• Posterior acoustic enhancement, where the ultrasound waves travel more easily through the fluid, creating increased brightness behind the cyst
• Lack of internal echoes, though some may contain debris or septations that appear as internal lines or echoes
• Thin and regular walls, with possible lateral edge shadowing at the borders
• No internal blood flow on color Doppler, helping to differentiate them from solid vascular masses These sonographic characteristics help radiologists distinguish cysts from solid masses, though sometimes additional imaging or aspiration may be needed for definitive diagnosis, as noted in 1 and 1. It's worth noting that the specific appearance of a cyst can vary depending on its location, size, and contents, with some complex cysts showing internal echoes due to hemorrhage, infection, or protein content, as described in 1 and 1. In general, simple cysts are considered benign and can be safely monitored with repeat imaging, as recommended by 1, while complex cysts may require further evaluation and management, as outlined in 1 and 1.

From the Research

Ultrasonographic Appearance of a Cyst

The ultrasonographic (US) appearance of a cyst can vary depending on the type and location of the cyst.

• Simple renal cysts are typically characterized by:
  • Lack of internal echoes
  • Increased posterior acoustic enhancement
  • Uniform round/oval shape
  • Thin posterior walls/demarcated borders 2
• Complex renal cysts may exhibit:
  • Septations
  • Calcifications
  • Internal echoes
  • Irregularities 2
• Infected renal cysts are often characterized by:
  • Thickened walls
  • Debris or gas
  • Calcifications with increased attenuation 2, 3
• Hemorrhagic cysts may appear with:
  • Echogenic debris
  • Irregular borders
  • Echogenic material within the walls and within the cyst 2

Variability in Cyst Appearance

The sonographic appearance of cysts can be variable, as seen in thyroglossal duct cysts, which can appear as:

• Anechoic masses
• Homogeneously hypoechoic with internal debris
• Pseudosolid masses
• Heterogeneous patterns 4, 5, 6 This variability highlights the importance of considering the clinical context and potentially using additional imaging modalities, such as CT or MRI, to further characterize the cyst 2.