Urinary obstruction means urine flow is blocked somewhere along its path — from the kidney (UPJ obstruction), along the ureter (ureteric stricture), or at the bladder exit (bladder outlet obstruction, often from an enlarged prostate). Blocked urine can back up, causing swelling, pain, infection, and — if untreated — kidney damage.
UPJ obstruction is the most common cause of kidney blockage detected before birth or in infancy, but can also present in adults. Bladder outlet obstruction is most common in men over 65, largely due to an enlarged prostate.
Causes & risk factors
- Enlarged prostate (BPH) — the leading cause of bladder outlet obstruction in men
- Scar tissue from prior surgery, ureteroscopy, or radiation (ureteric stricture)
- Congenital narrowing at the kidney-ureter junction (UPJ obstruction)
- Kidney stones or chronic/recurrent infections causing scarring
- Pelvic organ prolapse in women
- A blood vessel crossing the ureter
Symptoms to watch for
- Flank or back pain that may come and go with urine flow
- Weak urine stream, straining, or incomplete bladder emptying
- Frequent nighttime urination
- Recurrent UTIs or fevers from stagnant urine
- Complete inability to urinate is an emergency; severe flank pain with fever may signal an infected, blocked kidney
How it's diagnosed
- Ultrasound to detect kidney swelling (hydronephrosis)
- CT urogram or MRI for detailed anatomy
- Cystoscopy to view the bladder/urethra directly
- Urodynamic testing to measure flow and bladder pressure
- Post-void residual urine measurement
Treatment options
- Alpha-blocker medication: relaxes muscles to ease flow in BPH-related obstruction.
- Intermittent self-catheterization: manages retention without surgery.
- Dilation: stretches a narrowed ureter or urethral segment.
- Pyeloplasty: reconstructs the kidney-ureter junction in UPJ obstruction, often done robotically or laparoscopically.
- Urethroplasty/ureteral reconstruction: surgically removes and repairs the narrowed segment.
- Stent or nephrostomy tube: temporary drainage to relieve an urgent blockage.
Outlook & prevention
Most obstructions are highly treatable, especially when caught before kidney damage occurs — pyeloplasty for UPJ obstruction generally succeeds in over 90% of cases. Prompt treatment of UTIs and stones, plus monitoring after pelvic surgery, help prevent stricture formation.
- Inability to urinate, or urinating much less than usual
- Flank pain with fever or chills
- A progressively weaker urine stream or repeated UTIs