What are the differential diagnoses for urinary retention?

Differential Diagnosis for Urinary Retention

The differential diagnosis for urinary retention must be systematically organized into obstructive, neurologic, pharmacologic, infectious/inflammatory, and other causes, with benign prostatic hyperplasia accounting for 53% of cases in men. 1, 2

Obstructive Causes

In Men:

• Benign prostatic hyperplasia (BPH) - the most common cause overall, responsible for over half of all urinary retention cases 1, 2
• Urethral stricture - presents with decreased urinary stream, incomplete emptying, dysuria, and rising post-void residual; can be iatrogenic (most common from transurethral surgery), traumatic, or related to lichen sclerosus 3
• Prostate cancer - either from direct obstruction or as a complication of treatment 3
• Bladder neck contracture - often following prostate surgery 1
• Urethral stones or foreign bodies 3
• Urethral cancer - particularly associated with lichen sclerosus-related strictures 3
• Phimosis or meatal stenosis 1

In Women:

• Pelvic organ prolapse (cystocele, rectocele, uterine prolapse) - obstructive causes in women often involve pelvic organs 1, 2
• Urethral stricture - most commonly iatrogenic from painful/traumatic catheterization or multiple urethral dilations causing fibrosis; also from pelvic trauma, obstetric complications (cephalopelvic disproportion), malignancy, radiation, urethral/vaginal atrophy, recurrent infections, or lichen planus/lichen sclerosus 3
• Pelvic masses (fibroids, ovarian masses) 1
• Urethral diverticulum 4

In Both Sexes:

• Bladder stones 3
• Bladder cancer 3
• Fecal impaction/severe constipation - particularly important in elderly patients 5, 6

Neurologic Causes

Suprapontine Lesions (Intact Sensation):

• Cerebrovascular accident (stroke) - causes detrusor overactivity with preserved bladder sensation; patients feel urgency but cannot inhibit contractions 7
• Multiple sclerosis - can present with detrusor overactivity and preserved sensation 7
• Parkinson's disease 1
• Brain tumors 4

Spinal Cord Lesions (Impaired Sensation):

• Spinal cord injury/paraplegia - suprasacral lesions disrupt both motor and sensory pathways 7
• Cauda equina syndrome - produces lower motor neuron dysfunction with characteristically impaired perineal sensation and "paralyzed, insensate bladder" 7
• Myelomeningocele - sacral and lower spinal cord malformations with universal bladder dysfunction 7
• Spinal stenosis 4
• Transverse myelitis 1
• Spinal cord tumors 4

Peripheral Nerve Lesions:

• Diabetic neuropathy - autonomic dysfunction affecting bladder 1, 4
• Pelvic surgery complications (radical hysterectomy, abdominoperineal resection) 1
• Herniated disc with nerve root compression 4

Pharmacologic Causes

Up to 10% of urinary retention episodes are attributable to medication use, with elderly patients at highest risk due to comorbidities like BPH and polypharmacy. 8

Anticholinergic Medications:

• Antipsychotic drugs 8
• Antidepressants (particularly tricyclic antidepressants) 8
• Anticholinergic respiratory agents (ipratropium, tiotropium) 8
• Antihistamines 1
• Antispasmodics 8

Alpha-Adrenergic Agonists:

• Decongestants (pseudoephedrine, phenylephrine) 1, 8
• Sympathomimetics 8

Other Medications:

• Opioids and anesthetics - particularly perioperative 8
• Benzodiazepines 8
• NSAIDs 8
• Calcium channel antagonists 8
• Detrusor relaxants 8

Infectious and Inflammatory Causes

• Prostatitis - acute bacterial prostatitis commonly causes retention 1, 2
• Cystitis 1
• Urethritis 1
• Vulvovaginitis 1
• Urinary tract infections - particularly when associated with urethral stricture 3
• Herpes simplex virus (genital herpes causing sacral radiculopathy) 1
• Epididymitis 6

Other Causes

• Postoperative retention - particularly after anesthesia, pelvic/perineal surgery, or orthopedic procedures 8
• Psychogenic retention 4
• Detrusor underactivity/acontractility - bladder muscle failure from chronic overdistension or aging 4, 2
• Pelvic trauma - particularly posterior urethral injury in men from pelvic fractures 5
• Hypospadias surgery complications 3

Critical Diagnostic Considerations

When evaluating urinary retention, clinicians must distinguish between acute and chronic presentations, as this fundamentally changes management. 4, 2

• Acute urinary retention presents with hypogastric pain, inability to void, and palpable bladder; requires immediate catheter decompression 4
• Chronic urinary retention is often asymptomatic with elevated post-void residual (>300 mL on two occasions over six months); may present with overflow incontinence, recurrent UTIs, or renal insufficiency 3, 2
• Post-void residual measurement is essential for diagnosis - perform via bladder scanning or straight catheterization 5, 6

Common Pitfalls to Avoid:

• Do not assume a single etiology - multiple contributing factors often coexist, especially in elderly patients with BPH taking anticholinergic medications 8
• Do not overlook constipation - fecal impaction is a frequently missed reversible cause, particularly in geriatric populations 5, 6
• Do not miss cauda equina syndrome - this is a surgical emergency requiring urgent decompression; look for saddle anesthesia, bilateral leg weakness, and loss of anal sphincter tone 7
• Do not forget medication review - always obtain complete medication history including over-the-counter drugs and herbal supplements 2
• In trauma patients with blood at urethral meatus, do not attempt blind catheterization - perform retrograde urethrography first to rule out urethral injury 5