URINARY RETENTION
Melissa Mattison, M.D.
September 24, 2002
EPIDEMIOLOGY
Most common in men due to anatomical considerations
Usually older than 60 yo
Often occurs in men already having urinary symptoms (frequency, hesitancy etc)
Enlarged prostate increases risk almost twofold
High PSA, as it signifies increased prostate volume predisposes
Men s/p prostatectomy have 10x less risk of acute retention
Will happen to 10% of men in their 70’s in the next 5 years and 1/3 of men in their 80’s
PHYSIOLOGY
Normal Bladder Function
Filling Phase: Disorders here cause incontinence. The detrusor muscle is at rest via
beta-adrenergic receptors in the bladder wall being stimulated. Sympathetic stimulation
of alpha-adrenergic receptors in the internal sphincter muscles causes constriction.
External urethral sphincter and levator ani muscles act as back-up continence
mechanisms.
Emptying Phase: Disorders here lead to urinary retention. Emptying phase is initiated
when detrusor receptors are triggered as the bladder reaches its functional capacity
(350-650 mL). Urethra and levator ani muscles relax (moderated by inhibition of
pudental and sacral efferent nerves). Detrusor muscle contracts in synch with the
relaxation described above and urine is expelled. The detrusor muscle contraction is
moderated by cerebral cortex inhibition of relaxation.
Urinary retention
1) Any event or process that increases resistance to the flow of urine
a. Prostate enlargement
b. Tumor
c. In women, vaginal prolapse
2) Interruption of either sensory innervation of the bladder wall or the motor supply of the
bladder muscle (e.g., spinal cord disorder, neurogenic bladder from diabetes etc)
3) Impaired contractility
a. Bladder allowed to overdistend (e.g., during general anesthesia without
placement of a Foley catheter, or post-operatively when patient is given narcotics
+/- anticholinergics)
b. Fibrosis
c. Trauma
d. Inflammatory process within the bladder (tumor, infection, stones)
4) Lack of timing between urethral relaxation and bladder contraction
5) Side effects from drugs
a. Cough and cold preparations increase urethral closure pressure
b. Anticholinergics and calcium channel blockers cause detrusor relaxation
c. Antipsychotics cause decreased urethral pressure
SYMPTOMS
Often present with overflow incontinence (frequent small volume leakage or dribbling
due to detrusor weakness and/or bladder outlet obstruction)
Beth Israel Deaconess Medical Center Residents’ Report
Can present with symptoms of acute or chronic renal failure
Pain is usually present particularly if acute in onset
MANAGEMENT
Acutely: relieve the obstruction! Essential to avoid further renal damage.
Most agree that Foley catheterization is superior. In the past, suprapubic tubes were
considered as well.
Check renal function and urinalysis
Treat concomitant renal failure or post-obstructive diuresis if present.
Post-obstructive diuresis is usually physiologic – as excess fluid, urea and sodium that
have accumulated during the obstruction. Occasionally the diuresis will seem excessive
and fluids and electrolytes will need to be replaced. Typically half-normal saline is
recommended and electrolytes supplemented as needed.
Ultrasound will identify source of obstruction (lower versus upper)
There seems to be little foundation for the fear of precipitating hemorrhagic cystitis
Chronically:
Voiding Trial – predicting who will void successfully is tricky. 68% of patients who are
able to void spontaneously after removal of the catheter will develop acute retention
within one week. Recurrence is more likely in men > 75 yo, those whose initial urine
flow rate < 5 ml/s, or if the initial volume drained > 1L. To improve the chances of
success, consider waiting some period of time before initiating the voiding trial. If the
trial is attempted immediately, only 44% of the time is there success. If 7 days elapse
during which an indwelling Foley is in place, 62% of patients are successful. Consider
using Finasteride (inhibits formation of dihydrotestosterone to testosterone) or an alphablocker (e.g., terazosin, as it blocks the alpha-1-adrenergic receptors in the bladder neck
and prostate and relaxes smooth muscle).
Check post-void residual either using straight-catheterization after the patient attempts to
empty their bladder or with a “bladder scan” ultrasound.
Urodynamics – generally performed by Urology.
a) Urine Flow Rate (normal 12 mL/s for 150 mL void)
b) Cystometry - checks contractility and stability
c) Profilometry – urethral pressure measurement
d) Pressure Flow Study
Helpful to predict who will be aided by prostatectomy if performed after three or more
weeks of bladder rest. Predictors of poor outcome after prostatectomy (i.e., patients will
still require catheterization after the surgery) include old age (> 79 yrs), inability to void
during the pressure flow study, absence of unstable bladder contractions, and a maximal
detrusor pressure of < 20 cmH20.
Prostatectomy Generally best to defer surgery acutely and send the patient home with
an indwelling catheter (albeit understanding that the risk of bacterial colonization is 4%
per day), as surgical outcomes tend to be better when the patient is not acutely
recovering from renal failure and the bladder has had time to recover.
Stents – in the future, bladder neck and prostate stents may be used to relieve the
obstruction and allow the bladder to function normally
References:
BJU International 318, 921-925
BJU International 88, 178-182
British Journal of Urology 81, 712-720
Urology 58(2) 2001
Clinical Symposia 47(3) 1995
Beth Israel Deaconess Medical Center Residents’ Report