Bladder outlet obstruction
Bladder outlet obstruction (BOO) is mechanical resistance to urine flow at the bladder neck or urethra, most commonly from benign prostatic hyperplasia, that presents as lower urinary tract symptoms or acute urinary retention with a distended, tender bladder. Diagnosis is clinical, confirmed by an elevated postvoid residual on bladder ultrasound, and management is immediate catheter decompression for retention followed by treatment of the underlying cause.
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What this article covers
- Overview
Mechanical resistance to urine outflow at the bladder neck or urethra: bladder outlet obstruction (BOO) is anatomic, distinct from neurogenic or pharmacologic causes of urinary retention, and is more common in men.
- Epidemiology
BPH, the leading cause, becomes nearly universal with age: the prostate grows from about 20 cm3 in men under 30 to a size producing BPH in most men over 60; roughly half of men have BPH by age 60…
- Risk factors
Benign prostatic hyperplasia: the dominant cause in older men, from epithelial and stromal cell growth in the prostatic transition zone surrounding the urethra.
- Pathophysiology
Increased outflow resistance forces compensatory detrusor work: BPH-related epithelial and stromal proliferation narrows the prostatic urethra, and the detrusor muscle initially compensates with…
- Clinical features
Obstructive voiding symptoms: weak or intermittent urinary stream, hesitancy, straining to void, incomplete emptying, and postvoid dribbling.
- Differential diagnosis
Neurogenic bladder (detrusor underactivity or detrusor-sphincter dyssynergia): other sensory/reflex abnormalities in the S2-S4 distribution and a history of spinal cord injury, multiple sclerosis…
- Diagnosis
BOO is a clinical diagnosis based on obstructive/irritative voiding symptoms plus a suprapubic, tender, distended bladder on exam, confirmed by an elevated postvoid residual (PVR) on bladder…
- Management
First, in acute urinary retention, immediately decompress the bladder with urethral catheterization, or suprapubic catheterization if urethral access is not possible (for example, a tight urethral…
- Complications
Postrenal acute kidney injury: from bilateral hydronephrosis with sustained high-grade obstruction; renal recovery is generally good if relieved within 1-2 weeks, but uncorrected obstruction can…
- Prognosis
Renal recovery is generally good if the obstruction is relieved within 1-2 weeks, reflecting the largely reversible nature of postrenal AKI when addressed promptly.
- Prevention
Screen men over 50 years with lower urinary tract symptoms using the AUA/IPSS symptom index, with a score of 8 or higher (moderate to severe symptoms) prompting discussion of medical therapy before progression to retention.
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Related articles
- Benign prostatic hyperplasia (BPH)
Benign prostatic hyperplasia is age-related epithelial and stromal growth of the prostate transition zone causing bladder outlet obstruction and lower urinary tract symptoms in older men. Diagnosis rests on history, the AUA/IPSS symptom score, and a symmetrically enlarged, smooth prostate on digital rectal exam; management is staged from observation to alpha-1-blockers, 5-alpha-reductase inhibitors, and surgery.
- Neurogenic bladder
Neurogenic bladder is dysfunction of bladder storage or emptying caused by disease or injury of the central or peripheral nervous system, producing either a spastic, high-pressure bladder with urgency incontinence or an atonic, high-volume bladder with retention and overflow incontinence depending on lesion location. Diagnosis rests on the neurologic history and exam with urodynamic testing, and management is centered on a regular, low-pressure emptying regimen, most often clean intermittent catheterization, to protect renal function and prevent infection.
- Prostate cancer
Prostate cancer is the most commonly diagnosed cancer in men, usually found through an elevated PSA in an asymptomatic patient, with risk stratified by PSA, Grade Group (Gleason score), and TNM stage. Localized low-risk disease is often managed with active surveillance, while higher-risk and metastatic disease require radiation, surgery, or androgen deprivation therapy escalated through castrate-sensitive and castrate-resistant phases.
- Acute prostatitis
Acute bacterial prostatitis is a sudden bacterial infection of the prostate presenting with local urinary symptoms plus fever, chills, and a tender boggy prostate on exam. Diagnosis is clinical, confirmed by urinalysis and culture, and treatment is empiric antibiotics chosen by patient age and risk, continued for 2-4 weeks.
- Acute kidney injury
Acute kidney injury is a sudden rise in serum creatinine or fall in urine output from prerenal, intrinsic, or postrenal causes, defined and staged by KDIGO criteria. Management targets the underlying cause, corrects volume and electrolyte derangements, and escalates to renal replacement therapy for refractory hyperkalemia, acidosis, volume overload, or uremia.