The urinary bladder is a hollow, muscular organ in the pelvis that stores urine until it is expelled from the body through urination. On ultrasound, a normally distended bladder appears as a large, anechoic (black), thin-walled structure. Sonographers evaluate the bladder wall for thickening (which may indicate chronic outlet obstruction, cystitis, or tumor), masses (which may project into the lumen), calculi (stones that appear as echogenic foci with posterior shadowing), diverticula (outpouchings of the wall), and ureteral jets. Post-void residual volume is measured after the patient urinates to assess bladder emptying. A full bladder also serves as an acoustic window for transabdominal pelvic imaging, allowing visualization of the uterus and ovaries in women and the prostate in men.
Sonography Term