Garjae D. Lavien, MD
Michael J. Naslund, MD
BASICS
DESCRIPTION
• Bladder outlet obstruction (BOO) refers to a pathologic obstruction to urinary flow
• Definitions include the following:
– A reduction in urinary flow to <12 cc/s during a sustained detrusor contraction of over 40–50 cm H2O
– BOO index >40 on the International Continence Society nomogram based on urodynamic testing
EPIDEMIOLOGY
Incidence
2.2–6.8 events of acute urinary retention per 1,000 person years (1)[A]
Prevalence
None
RISK FACTORS
• Increasing age
– Microscopic BPH starts as early as the 30s but clinical BPH usually presents after the age of 50
• Infection
• Urethral trauma
• Pelvic radiation
• Prior urologic procedures
Genetics
N/A
PATHOPHYSIOLOGY
• BOO can be due to both static and dynamic factors:
• Dynamic factors
– Stimulation or lack of relaxation of the smooth muscle along the proximal urethra or bladder neck
– Results in increased resistance along the prostatic urethra
• Static factors
– Constricted outlet by enlarged prostatic tissue, bladder neck contracture, or urethral stricture
• Outlet obstruction leads to detrusor hypertrophy and the symptoms of BOO
ASSOCIATED CONDITIONS
• BPH
• Urethral stricture disease
• Detrusor sphincter dyssynergia
GENERAL PREVENTION
None
DIAGNOSIS
HISTORY
• Detailed description of obstructive voiding symptoms consistent with BOO
– Slow urinary stream
– Urinary hesitancy
– Intermittent urinary stream
– Straining to void
– Sense of incomplete bladder emptying
– Urinary retention
• History of irritative symptoms
• Medical history of gynecologic, neurologic, and GI illness
• Past surgical history for pelvic and spinal procedures
• Medication review for anticholinergics, α-agonists, psychotropic agents
• Voiding diary
• International Prostate Symptom Score
PHYSICAL EXAM
• Abdominal exam:
– Palpate for bladder distention (>150 cc retained urine needed to be palpable in an adult)
– Inguinal hernia can be associated with severe BPH and retention
• Digital rectal exam:
– Examine for an enlarged prostate
– Note any findings suspicious for cancer: Nodules, firmness, and asymmetry
– Assess anal sphincter tone
• Pelvic exam (women) for pelvic organ prolapse and urethral diverticula
• Neurologic exam for gross defects
DIAGNOSTIC TESTS & INTERPRETATION
Lab
• PSA:
– If elevated, consider prostate cancer, prostatic inflammation, benign prostatic hyperplasia
• Urinalysis:
– If hematuria or urinary infection is present, further evaluation is necessary (see Chapter on “Hematuria, Gross and Microscopic, Adult”)
• Creatinine
– Not necessary unless patient is in urinary retention
Imaging
• Renal and bladder US
– Evaluate for hydronephrosis if there is renal insufficiency
– Allows noninvasive determination of PVR
• Upper tract imaging with CT urogram to evaluate causes of hematuria
• Uroflowmetry:
– Measures peak flow, demonstrate voiding pattern, and voided volume
– Peak flow <10–12 cc/s (for voided volume >150 cc) is suggestive of obstruction, although an acontractile bladder cannot be ruled out
• Cystoscopy: Endoscopic evaluation of urethra and bladder
– Used to evaluate prostatic length, median lobe component of prostatic obstruction, and bladder mucosa
– Can reveal other etiology for the BOO, such as strictures, stones, diverticula, urethral masses, and bladder tumors
• Urodynamics: Pressure-flow study to determine if a low flow rate is due to obstruction or reduced bladder contractility:
– Videourodynamics: Fluoroscopy combined with urodynamics. Recommended in patient suspected to have primary bladder neck obstruction
– ICS nomogram is the most widely used measurement of BOO; plots maximal flow against detrusor pressure at the time of flow
– EMG: Evaluates for neurogenic etiology of BOO
Diagnostic Procedures/Surgery
See “Imaging” and “Surgery/other procedures”
Pathologic Findings
Depends on etiology of BOO
DIFFERENTIAL DIAGNOSIS
• Inadequate bladder contractility
• BOO after incontinence surgery
– The most common etiology of BOO/urinary retention in women
• Prostatic obstruction (BPH)
– Most common etiology of BOO in men
• Primary bladder neck obstruction
• Infection:
– Prostatitis, intraurethral condyloma (men and woman), periurethral abscess
• Neurologic:
– Detrusor sphincter dyssynergia, diabetes mellitus with atonic bladder
• Medications that affect bladder contractility
– Anesthetics, narcotic, psychotropics
• Urethral caruncle, urethral diverticulum (primarily women)
• Urethral cancer
• Penile cancer (usually advanced)
TREATMENT
GENERAL MEASURES
• Management of BOO depends on etiology and severity.
• A urethral catheter is used for temporary management of severe obstruction or retention.
• A suprapubic tube is used if a urethral catheter cannot be placed (severe stricture or BPH) or urethral catheter is contraindicated (acute prostatitis).
• Long-term treatment of BOO is medical and surgical.
MEDICATION
First Line
• α-Blockers: Rapidly relax the smooth muscle of the bladder neck and prostate without impairing bladder contractility:
– Alfuzosin (10 mg/d)
– Doxazosin (start 1 mg/d to max 8 mg; XL form 2–8 mg daily)
– Silodosin (8 mg/d)
– Tamsulosin (start 0.4 mg to max 0.8 mg)
– Terazosin (start 1 mg/d to max 20 mg)
• 5-α-reductase inhibitors in males: Effective in larger glands (>40 cc) to reduce prostate size, improve symptoms, and reduce progression risk:
– Finasteride (5 mg/d)
– Dutasteride (0.5 mg/d)
Second Line
• Phosphodiesterase-5 inhibitors (PDE5i) in males
– Tadalafil only PDE5i currently approved by the FDA for treatment of LUTS in the setting of BPH with or without coexisting erectile dysfunction (2)[A]
SURGERY/OTHER PROCEDURES
• Urethral strictures
– Urethral dilation
– Endoscopic incision
– Open excision (with primary anastomosis, grafts, or flaps)
• Urethrolysis
– Primary surgical approach to urethral obstruction following anti-incontinence surgery in women
• Sphincterotomy
– Utilized for patients with detrusor sphincter dyssynergia
• BPH
– Transurethral needle ablation
– Transurethral microwave therapy
– Transurethral incision of prostate
– Transurethral resection of prostate (TURP)
– Laser-assisted techniques such as holmium laser enucleation of the prostate (HoLEP), others
– Photovaporization of prostate
– Simple open prostatectomy
ADDITIONAL TREATMENT
Radiation Therapy
N/A
Additional Therapies
• Long-term catheter drainage for patients with severe comorbidities
• Clean intermittent catheterization
• Prostatic stents
• Urinary diversion
Complementary & Alternative Therapies
• Saw Palmetto (Serenoa Repens)
– No difference in reduction of lower urinary tract symptoms compared to placebo (3)[A]
ONGOING CARE
PROGNOSIS
Excellent with definitive management
COMPLICATIONS
• Urinary retention
• Gross hematuria
• Renal insufficiency/failure
• Bladder stones
• UTIs
• Bladder diverticula and flaccid bladder
• Postobstructive diuresis:
– Occurs with severe BOO and bilateral ureteral obstruction due to urinary retention
– Self-limited and corrected by the fluid hydration
– If the patient cannot keep up with the urine output, then IV replacement with 1/2 normal saline at a rate of 1/2 of the urine output
– Serum electrolytes must be monitored closely
FOLLOW-UP
Patient Monitoring
• Periodic follow-up visits to assess symptom progression (IPSS)
• Yearly urinalysis and PSA measurement
• Serial measurement of uroflow and PVR urine
• Counsel on the possibility of progression of symptoms and complications
• Management of BPH does not eliminate the risk of developing prostate cancer
Patient Resources
• Urology Care Foundation
– www.urologyhealth.org
REFERENCES
1. Kaplan SA, Wein AJ, Staskin DR, et al. Urinary retention and post-void residual urine in men: Separating truth from tradition. J Urol. 2008;180:47–54.
2. Dmochowski R, Roehrborn C, Klise S, Xu L, et al. Urodynamic effects of once daily tadalafil in men with lower urinary tract symptoms secondary to clinical benign prostatic hyperplasia: A randomized, placebo controlled 12-week clinical trial. J Urol. 2013;189;S135–S140.
3. Barry MJ, Meleth S, Lee JY, et al; Complementary and Alternative Medicine for Urological Symptoms (CAMUS) Study Group. Effect of increasing doses of saw palmetto extract on lower urinary tract symptoms: A randomized trial. JAMA. 2011;306(12):1344–1351.
ADDITIONAL READING
• Dmochowski RR. Bladder outlet obstruction: Etiology and evaluation. Rev Urol. 2005;7:S3–S13.
• Groutz A, Blaivas JG, Chaikin DC. Bladder outlet obstruction in women: Definition and characteristics. Neurourol Urodyn. 2000;12:213.
• Lepor H. Pathophysiology of benign prostatic hyperplasia in the aging male population. Rev Urol. 2005;7:S3–S12.
• McConnell JD, Roehrborn CG, Bautista OM, et al. The long-term effect of doxazosin, finasteride, and combination therapy on the clinical progression of benign prostatic hyperplasia. N Engl J Med. 2003;349:2387–2398.
See Also (Topic, Algorithm, Media)
• Bladder Neck Contracture
• Bladder Neck Hypertrophy
• Bladder Outlet Obstruction (BOO) Image 
• Lower Urinary Tract Symptoms (LUTS)
• Lower Urinary Tract Symptoms (LUTs), Male Algorithm 
• Multiple Sclerosis, Urologic Considerations
• Prostate, Benign Enlargement (Benign Prostate Enlargement (BPE)
• Prostate, Benign Hyperplasia (BPH)
• Prostate, Benign Obstruction (Benign Prostatic Obstruction, [BPO])
CODES
ICD9
• 596.0 Bladder neck obstruction
• 600.01 Hypertrophy (benign) of prostate with urinary obstruction and other lower urinary tract symptoms (LUTS)
• 788.29 Other specified retention of urine
ICD10
• N32.0 Bladder-neck obstruction
• N40.1 Enlarged prostate with lower urinary tract symptoms
• R33.8 Other retention of urine
CLINICAL/SURGICAL PEARLS
• If a male patient has lower urinary tract symptoms check to ensure a low post-void residual which generally confirms that treatment is not necessary.
• Strong consideration should be given for evaluation for multiple sclerosis in young female patients with new onset urinary retention.