Bladder outlet obstruction occurs when something blocks the normal flow of urine out of the bladder and into the urethra. The most common cause in men is benign prostatic hyperplasia, where the enlarged prostate squeezes the urethra shut. Other causes include urethral strictures, bladder stones lodged at the bladder neck, and pelvic organ prolapse in women. On ultrasound, signs of bladder outlet obstruction include a large post-void residual volume, thickening of the bladder wall from the muscle working harder to push urine past the blockage, trabeculation of the bladder wall, and potentially hydronephrosis in the kidneys from the backup of urine.
Sonography Term