Urinary Retention

How the bladder normally empties

Emptying requires a bladder muscle (detrusor) strong enough to contract, an outlet (bladder neck, prostate, urethra) that opens, and intact nerves from the brain and lower spinal cord coordinating both. Retention happens when the outlet is blocked, the muscle is weak, or the nerves fail.

Acute vs chronic urinary retention

Acute-on-chronic retention is when a person with chronic retention suddenly cannot void at all, often with a very large bladder volume.

Causes

• Obstruction: benign prostatic hyperplasia, prostate cancer, urethral stricture, bladder stones, clots, constipation, pelvic organ prolapse, pelvic masses, and in boys, posterior urethral valves.
• Medicines: anticholinergics, antihistamines, decongestants, opioids, tricyclic antidepressants, and anesthesia.
• Neurological: diabetes, multiple sclerosis, Parkinson's disease, stroke, spinal cord injury, cauda equina syndrome, pelvic nerve injury. See neurogenic bladder.
• Detrusor underactivity: a weak bladder muscle from aging or long-term overdistension, called an atonic bladder.
• Infection and inflammation: acute prostatitis, cystitis, genital herpes.
• Postoperative and postpartum: pain, opioids, epidural anesthesia, immobility and swelling.

Symptoms

Acute retention causes a painful urge with no flow and a tense, tender lower belly. Chronic retention causes a weak stream, hesitancy, straining, frequency, nocturia, a sense of incomplete emptying, recurrent infections and overflow incontinence. The symptom guide on being unable to urinate covers what to do in the moment.

Diagnosis

1. Bladder scan (ultrasound): measures the volume of urine in the bladder, and the post-void residual (PVR) after urinating. A PVR consistently above about 300 ml defines chronic retention in AUA consensus guidance, though smaller residuals can matter.
2. Physical examination: palpable bladder, rectal exam for prostate size and constipation, pelvic exam in women, and a neurological exam including saddle sensation and reflexes.
3. Urinalysis and culture for infection and blood.
4. Blood tests: creatinine and electrolytes for kidney function. PSA may be checked in men, but it is falsely raised by retention and catheterization, so timing matters.
5. Kidney ultrasound to look for hydronephrosis (back-pressure swelling).
6. Further tests: urodynamics to distinguish obstruction from a weak bladder, cystoscopy to inspect the urethra and bladder, and MRI of the spine when a nerve cause is suspected.

Treatment

Immediate drainage

A urethral catheter drains the bladder. If a urethral catheter cannot be passed (for example with a stricture), a suprapubic catheter is placed through the lower belly. After drainage of a very large volume, the kidneys may produce large amounts of urine for a time (post-obstructive diuresis), so fluids and blood salts are monitored.

Trial without catheter

For acute retention from an enlarged prostate, an alpha-blocker (such as tamsulosin) is started, and the catheter is removed after a few days to see if the person can void. Starting the alpha-blocker increases the chance of success. Triggers such as constipation and medicines are addressed at the same time.

Treating an enlarged prostate

• Medicines: alpha-blockers relax the prostate. 5-alpha reductase inhibitors (finasteride, dutasteride) shrink it over 6 to 12 months and reduce the risk of future retention.
• Surgery: transurethral resection of the prostate (TURP), laser enucleation or vaporization, and other minimally invasive procedures relieve the blockage. Surgery is usually advised after a failed trial without catheter or for recurrent retention.

Long-term drainage

• Clean intermittent self-catheterization (CISC): the preferred option when the bladder muscle is weak, done several times a day.
• Indwelling urethral or suprapubic catheter when self-catheterization is not possible.

Other treatments

Urethral stricture dilation or reconstruction, prolapse repair, sacral neuromodulation for some types of non-obstructive retention, and treatment of neurological disease.

Complications

• urinary tract infections and, from catheters, catheter-associated infection
• bladder stones
• bladder overdistension injury, which can permanently weaken the muscle
• kidney damage from back-pressure, especially in high-pressure chronic retention
• bleeding after rapid decompression (usually minor)

Outlook

Many people with acute retention from a temporary trigger void normally after a trial without catheter. Retention due to an enlarged prostate often recurs without definitive treatment, but prostate surgery is highly effective. Chronic retention with a weak bladder usually needs ongoing management, and regular kidney checks keep it safe over the long term.

Frequently asked questions

What is the difference between acute and chronic urinary retention?

Acute retention is sudden, painful and complete: you cannot pass urine. Chronic retention develops slowly, is usually painless, and leaves a large volume of urine behind after you void. Acute retention needs urgent catheter drainage; chronic retention needs assessment and long-term management.

How is urinary retention diagnosed?

With a bladder ultrasound scan that measures the urine left after you void (post-void residual), plus an examination, urine tests and kidney blood tests. Urodynamic studies and cystoscopy may be used to find the cause.

What is the treatment for urinary retention?

The bladder is drained with a catheter first. Then the cause is treated: alpha-blockers and sometimes surgery for an enlarged prostate, stopping problem medicines, treating constipation or infection. Some people need intermittent self-catheterization long term.

Can urinary retention damage the kidneys?

Yes. Chronic retention, especially high-pressure retention, can cause urine to back up into the kidneys (hydronephrosis) and lead to kidney failure if untreated. Draining the bladder usually allows kidney function to recover, at least partly.