Urinary retention may be
Acute
Chronic
Causes include impaired bladder contractility, bladder outlet obstruction Established incontinence Urinary incontinence is involuntary loss of urine; some experts consider it present only when a patient thinks it is a problem. The disorder is greatly underrecognized and underreported. Many... read more , detrusor-sphincter dyssynergia Established incontinence Urinary incontinence is involuntary loss of urine; some experts consider it present only when a patient thinks it is a problem. The disorder is greatly underrecognized and underreported. Many... read more (lack of coordination between bladder contraction and sphincter relaxation), or a combination. (See also Overview of Voiding Overview of Voiding Voiding disorders affect urine storage or release because both are controlled by the same neural and urinary tract mechanisms. The result is incontinence or retention. For normal urinary function... read more .)
Retention is most common among men, in whom prostate abnormalities or urethral strictures Urethral Stricture Urethral stricture is scarring that obstructs the anterior urethral lumen. Urethral stricture can be Congenital Acquired Anything that damages the urethral epithelium or corpus spongiosum can... read more cause outlet obstruction. In either sex, retention may be due to drugs (particularly those with anticholinergic effects, including many over-the-counter drugs), severe fecal impaction Fecal impaction Constipation is difficult or infrequent passage of stool, hardness of stool, or a feeling of incomplete evacuation. (See also Constipation in Children.) No bodily function is more variable and... read more (which increases pressure on the bladder trigone), or neurogenic bladder Neurogenic Bladder Neurogenic bladder is bladder dysfunction (flaccid or spastic) caused by neurologic damage. Symptoms can include overflow incontinence, frequency, urgency, urge incontinence, and retention.... read more in patients with diabetes Diabetes Mellitus (DM) Diabetes mellitus is impaired insulin secretion and variable degrees of peripheral insulin resistance leading to hyperglycemia. Early symptoms are related to hyperglycemia and include polydipsia... read more , multiple sclerosis Multiple Sclerosis (MS) Multiple sclerosis (MS) is characterized by disseminated patches of demyelination in the brain and spinal cord. Common symptoms include visual and oculomotor abnormalities, paresthesias, weakness... read more 
, Parkinson disease Parkinson Disease Parkinson disease is a slowly progressive, degenerative disorder characterized by resting tremor, stiffness (rigidity), slow and decreased movement (bradykinesia), and eventually gait and/or... read more , or prior pelvic surgery resulting in bladder denervation.
Urinary retention can be asymptomatic or cause urinary frequency Urinary Frequency Urinary frequency is the need to urinate many times during the day, at night (nocturia), or both but in normal or less-than-normal volumes. Frequency may be accompanied by a sensation of an... read more , a sense of incomplete emptying, and urge or overflow incontinence. It may cause abdominal distention and pain. When retention develops slowly, pain may be absent. Long-standing retention predisposes to UTI and can increase bladder pressure, causing obstructive uropathy Obstructive Uropathy Obstructive uropathy is structural or functional hindrance of normal urine flow, sometimes leading to renal dysfunction (obstructive nephropathy). Symptoms, less likely in chronic obstruction... read more .
Diagnosis
Measurement of postvoid residual volume
Diagnosis is obvious in patients who cannot void. In those who can void, incomplete bladder emptying is diagnosed by postvoid catheterization or ultrasonography Ultrasonography Imaging tests are often used to evaluate patients with renal and urologic disorders. Abdominal x-rays without radiopaque contrast agents may be done to check for positioning of ureteral stents... read more 
showing an elevated residual urine volume. A volume < 50 mL is normal; < 100 mL is usually acceptable in patients > 65 but abnormal in younger patients. Other tests (eg, urinalysis, blood tests, ultrasonography, urodynamic testing, cystoscopy Cystoscopy Cystoscopy is insertion of a rigid or flexible fiberoptic instrument into the bladder. Indications include the following: Helping diagnose urologic disorders (eg, bladder tumors, calculi in... read more 
, cystography) are done based on clinical findings.
Treatment
Urethral catheterization and treatment of cause
Relief of acute urinary retention requires urethral catheterization Urethral catheterization Bladder catheterization is used to do the following: Obtain urine for examination Measure residual urine volume Relieve urinary retention or incontinence Deliver radiopaque contrast agents or... read more . Subsequent treatment depends on cause. In men with benign prostatic hyperplasia Benign Prostatic Hyperplasia (BPH) Benign prostatic hyperplasia (BPH) is nonmalignant adenomatous overgrowth of the periurethral prostate gland. Symptoms are those of bladder outlet obstruction—weak stream, hesitancy, urinary... read more , drugs (usually alpha-adrenergic blockers or 5-alpha-reductase inhibitors) or surgery may help decrease bladder outlet resistance.
No treatment is effective for impaired bladder contractility; however, reducing outlet resistance with alpha-adrenergic blockers may increase bladder emptying.
Intermittent self-catheterization or indwelling catheterization is often required. An indwelling suprapubic tube or urinary diversion is a last resort.
Key Points
Mechanisms include impaired bladder contractility, bladder outlet obstruction, and detrusor-sphincter dyssynergia.
Incomplete retention is diagnosed by a postvoid residual volume > 50 mL (> 100 mL in patients > 65).
Prescribe urethral catheterization and treat the cause of retention.
