Bladder Outlet Obstruction (BOO)

What is bladder outlet obstruction? 

Bladder outlet obstruction (BOO) is a blockage that occurs at the base of the bladder. As a result, it reduces or ceases the flow of urine into the urethra. The urethra is the tube that carries urine out of the body.


Bladder outlet obstruction is common is aging men. It is often caused by an enlarged prostate (in men), bladder stones or bladder cancer. The chances of having these occur increases greatly as a man ages.

Other common causes may include:

  • Pelvic tumors (cervix, prostate, uterus, rectum).
  • Narrowing of the urethra, due to scar tissue or certain birth defects.

Less common causes may include:

  • Cystocele (when the bladder falls into the vagina)
  • Foreign objects
  • Urethral or pelvic muscle spasms
  • Inguinal (groin) hernia


  • Abdominal pain.
  • Continuously feeling like you have a full bladder.
  • Urinary Frequency
  • Pain during urination (dysuria)
  • Problems commencing urination (urinary hesitancy)
  • Slow, uneven urine flow, or at times being unable to urinate.
  • Straining to urinate.
  • Urinary tract infection.


  • Medication:

Finasteride and dutasteride are the two currently available 5-alpha-reductase inhibitors used to control bladder outlet obstruction symptoms. Unlike the alpha-blocking agents, these medications relieve bladder outlet obstruction by shrinking the prostate to allow the passage of urine.

  • Surgery

Surgery is used for long term treatment of Bladder Outlet Obstruction. 

  • Catheterisation:

​​​​​​​Either an indwelling urethral catheter or Suprapubic catheter will be left insitu.