Anechoic areas are regions without internal echoes (echo free). Cysts or fluid filled regions are anechoic and may demonstrate enhanced echoes posterior to the fluid.

An imaging plane, perpendicular to the ground, the coronal plane separates the anterior from the posterior part (the front from the back).

Sonography of the gallbladder is a reliable technique for diagnosing e.g., gallstones, cholecystitis, tumors, polyps, or ductal obstruction. Patient should be examined with empty stomach and on a low fat diet the night before. Barium studies, endoscopy, ERCP, colonoscopy, and abdominal CT should be performed after this examination.
Gallbladder ultrasound is best performed with a 5 MHz curved array or a linear array transducer in cases of a very superficial gallbladder. In obese patients or in patients with difficult sonographic access, a 3.5 MHz sector or curved linear transducer is advantageous.
Gallbladder and biliary tree are usually imaged in supine and posterior oblique (LPO) positions. Sometimes very small gallstones are better visible in upright and prone position.

Reflux sonography, as an alternative to micturating cystography (MCU), evaluates vesico-ureteral reflux (VUR), a common problem in children. Contrast enhanced pulse-inversion imaging shows best results. During the instillation of an ultrasound contrast agent into the bladder, (as for a conventional MCU) the lower ureters and renal pelves are scanned transabdominally as the bladder is filled to stimulate micturition.
Advantages for reflux sonography are a high sensitivity and the avoidance of X-rays. A disadvantage is the poorer depiction of the posterior urethra. However, for girls and for all follow-up studies, the ultrasound MCU has become standard in many pediatric ultrasound departments.

See also Urologic Ultrasound, Kidney Ultrasound, Ultrasound Safety, Ultrasound Imaging Modes.