What are the possible causes of acute urinary retention in a 31‑year‑old?

Differential Diagnosis of Acute Urinary Retention in a 31-Year-Old

In a 31-year-old presenting with inability to urinate, the differential diagnosis must prioritize obstructive causes (urethral stricture, acute prostatitis), neurologic etiologies (spinal cord pathology, cauda equina syndrome), medication-induced retention (anticholinergics, sympathomimetics), and infectious/inflammatory causes (severe urethritis, pelvic abscess), with immediate bladder decompression followed by targeted diagnostic evaluation. 1, 2, 3

Immediate Assessment and Management

Initial Stabilization

• Perform urgent bladder catheterization to achieve complete decompression; if urethral catheterization fails, place a suprapubic catheter. 1, 4
• Use bladder scanning or measure post-catheterization volume to confirm retention and quantify residual urine. 1
• Assess renal function with serum creatinine and BUN, as urinary retention can cause post-renal acute kidney injury; order renal ultrasound if creatinine is elevated (>90% sensitivity for hydronephrosis). 4

Obstructive Causes (Most Common in Young Men)

Urethral Stricture

• Urethral stricture is the leading obstructive cause in young men with normal prostate size and should be diagnosed with retrograde urethrogram. 1
• History of prior urethral instrumentation, catheterization, sexually transmitted infections (especially gonorrhea), or pelvic trauma strongly suggests stricture. 1, 2
• If blood is present at the urethral meatus after pelvic trauma, perform retrograde urethrography before attempting catheterization to rule out urethral injury. 1
• Treatment options include urethral dilation, direct visual internal urethrotomy, or urethroplasty depending on stricture length and location. 1

Acute Prostatitis

• Severe bacterial prostatitis can cause acute retention through prostatic edema and inflammation. 2, 3
• Patients present with fever, perineal pain, dysuria, and an exquisitely tender prostate on digital rectal examination. 2
• Obtain urinalysis and urine culture; initiate empiric antibiotics (fluoroquinolone or third-generation cephalosporin) while awaiting culture results. 1

Phimosis or Paraphimosis

• Severe phimosis (inability to retract foreskin) or paraphimosis (trapped retracted foreskin) can obstruct urethral flow. 2, 3
• Physical examination of external genitalia will reveal the diagnosis. 5

Neurologic Causes (Critical to Identify)

Spinal Cord Pathology

• Any neurologic signs suggesting spinal cord compression or cauda equina syndrome require urgent neurosurgical consultation. 6, 1
• Screen for saddle anesthesia, lower extremity weakness, decreased rectal tone, bilateral leg pain, or recent back trauma. 5, 3
• Spinal dysraphism with tethered cord can present with new-onset urinary retention, especially if accompanied by fecal incontinence, leg pain, or gait disturbance. 5
• Obtain urgent MRI of the spine if any neurologic red flags are present. 3

Multiple Sclerosis or Demyelinating Disease

• New-onset urinary retention in a young adult may represent the first manifestation of multiple sclerosis. 2, 3
• Inquire about prior episodes of vision changes, limb weakness, or sensory disturbances. 3
• Neurologic examination should assess for upper motor neuron signs, sensory deficits, and cranial nerve abnormalities. 6

Acute Transverse Myelitis

• Viral or post-infectious inflammation of the spinal cord can cause acute retention with bilateral leg weakness and sensory level. 3

Medication-Induced Retention

Anticholinergic Medications

• Review all medications including over-the-counter antihistamines (diphenhydramine), tricyclic antidepressants, antipsychotics, and bladder antimuscarinics. 5, 6
• Anticholinergics impair detrusor contractility and are a common iatrogenic cause in young adults. 2, 7

Sympathomimetic Agents

• Decongestants containing pseudoephedrine or phenylephrine increase bladder neck tone and can precipitate retention. 1, 2
• Inquire specifically about cold medications, energy supplements, and weight-loss products. 2

Opioid Medications

• Opioids decrease detrusor contractility and increase sphincter tone, particularly in postoperative settings. 6, 2

Infectious and Inflammatory Causes

Severe Urethritis

• Gonococcal or chlamydial urethritis with marked urethral edema can obstruct flow. 2, 3
• Obtain urethral swab for gonorrhea/chlamydia testing and urinalysis. 5, 1

Pelvic Abscess or Severe Cystitis

• Pelvic or perinephric abscess can compress the bladder neck or urethra. 3
• Severe hemorrhagic cystitis with clot retention can mimic obstructive retention. 2

Herpes Simplex Virus (HSV) Infection

• Primary genital HSV can cause sacral radiculopathy with neurogenic retention. 2, 3
• Examine for genital vesicles or ulcers; inquire about recent sexual exposure. 3

Other Important Causes

Constipation and Fecal Impaction

• Severe constipation is a frequently overlooked cause, especially in patients with limited mobility or opioid use. 5, 6, 4
• Perform digital rectal examination to assess for impaction. 5

Psychogenic Retention

• Rare in this age group but can occur in the setting of severe anxiety or psychiatric illness. 2
• This is a diagnosis of exclusion after ruling out organic causes. 2

Bladder Calculus

• Large bladder stone can obstruct the bladder neck, particularly with positional changes. 1, 2

Diagnostic Algorithm

History Red Flags

• Fever, flank pain, or systemic symptoms: suggests infection, abscess, or pyelonephritis requiring urgent imaging and antibiotics. 1, 4
• Recent trauma or instrumentation: raises concern for urethral injury or stricture. 1
• Neurologic symptoms (weakness, numbness, saddle anesthesia): mandates urgent spinal imaging. 5, 1
• New medications or substance use: consider drug-induced retention. 6, 2

Physical Examination Priorities

• Focused neurologic exam including lower extremity strength, sensation, reflexes, and rectal tone. 6, 3
• External genitalia examination for phimosis, meatal stenosis, or herpetic lesions. 5, 2
• Digital rectal examination to assess prostate size/tenderness and check for fecal impaction. 5
• Suprapubic palpation and percussion for bladder distension. 8

Essential Diagnostic Tests

• Urinalysis to identify infection, hematuria, or glycosuria. 5, 1
• Post-void residual measurement (via catheterization or ultrasound); volumes >300-500 mL confirm retention. 6, 1
• Serum creatinine and BUN to assess for obstructive nephropathy. 4
• Renal ultrasound if creatinine is elevated or if chronic retention is suspected. 4
• Retrograde urethrogram if urethral stricture or injury is suspected. 1
• Spine MRI if any neurologic red flags are present. 3

Common Pitfalls to Avoid

• Do not assume benign prostatic hyperplasia in a 31-year-old; BPH is exceedingly rare before age 40 and alternative diagnoses must be pursued. 2, 7
• Do not miss spinal cord compression; failure to obtain urgent imaging in the presence of neurologic signs can result in permanent neurologic deficit. 5, 1
• Do not overlook medication history; many young adults take over-the-counter medications or supplements without reporting them. 6, 2
• Do not delay catheterization while pursuing diagnostic workup; prolonged bladder distension can cause detrusor injury and post-obstructive diuresis. 1, 8
• Do not perform blind urethral catheterization if urethral injury is suspected; this can convert a partial injury into complete disruption. 1
• Do not discharge a patient after successful catheter removal without arranging close urology follow-up; the risk of recurrent retention remains elevated. 1, 4