Ultrasound Appearance of Kidney Stones
I cannot provide you with an actual ultrasound image, but I can describe what kidney stones look like on ultrasound imaging.
Sonographic Characteristics of Kidney Stones
On ultrasound, kidney stones appear as bright (hyperechoic) structures within the kidney that cast an acoustic shadow behind them. 1
Key Imaging Features:
Echogenic focus: The stone itself appears as a bright white spot due to its high reflectivity 1
Posterior acoustic shadowing: A dark shadow extends behind the stone, which is the hallmark finding that helps distinguish stones from other bright structures 1
Twinkling artifact: When color Doppler is applied, stones produce a characteristic multicolored signal (appearing as an intense multicolored pattern deep to the stone), which can improve detection of small stones 1
Limitations of Ultrasound for Stone Detection
Ultrasound has significant limitations compared to CT scanning, with an overall sensitivity of only 54% for detecting kidney stones. 2
Important Caveats:
Small stones are frequently missed: Renal stones smaller than 3 mm are usually not identified by current sonographic equipment 1
Size overestimation: Ultrasound significantly overestimates stone size in the 0-10 mm range, which can lead to inappropriate treatment recommendations in approximately 22% of cases 2
Stones may be obscured: The echogenicity of stones is similar to surrounding renal sinus fat, making detection challenging 1
Absence of hydronephrosis doesn't exclude stones: Many ureteral stones, especially small ones, do not cause visible hydronephrosis on ultrasound 1
Clinical Context
Non-contrast CT remains the gold standard for kidney stone imaging, with sensitivity as high as 97%, compared to ultrasound's 54% sensitivity. 1, 3, 4 However, ultrasound is appropriate as the initial imaging modality in pregnant patients to avoid radiation exposure 1, and can be useful for detecting signs of obstruction (hydronephrosis) even when the stone itself is not visualized 1.