Acute Urinary Retention

What is Acute Urinary Retention?

Acute urinary retention (AUR) is a medical emergency characterized by sudden, complete inability to pass urine despite a full bladder. Unlike chronic urinary retention, which develops gradually, acute retention comes on suddenly and causes significant pain and distress.

This condition requires immediate medical attention to relieve the bladder and prevent complications including bladder damage, kidney injury, and autonomic dysreflexia in patients with spinal cord conditions.

How Common is Acute Urinary Retention?

Acute urinary retention affects men far more often than women, with a ratio of approximately 10:1. The lifetime risk for men over age 70 approaches 10%, and incidence increases with age. Hospital admission rates reach 2-3 per 1,000 men over 70 annually. Post-operative urinary retention is a common complication following surgery under general anesthesia.

Symptoms

Classic Presentation

The hallmark symptom is complete inability to urinate despite a strong urge. Patients typically experience severe suprapubic (lower abdominal) pain, visible or palpable bladder distension, and significant restlessness and agitation. Physical examination reveals a distended, tender lower abdomen with dullness to percussion over the bladder area.

Painless Retention

Some patients present with relatively painless retention, particularly those with neurogenic bladder, diabetes with neuropathy, advanced age, or decompensated chronic retention. Despite the absence of severe pain, treatment remains urgent.

Causes

Prostatic Causes in Men

Benign prostatic hyperplasia (BPH) is the most common cause in men. Gradual prostate enlargement eventually causes complete urethral obstruction. Prostate cancer represents a less common but important cause. Acute prostatitis can trigger retention through prostatic swelling and inflammation.

Urethral Causes

Urethral stricture narrows the urethral passage and may progress to complete obstruction. Bladder stones or urethral stones can lodge at the bladder neck. In men, phimosis (tight foreskin) and urethral trauma are additional considerations.

Causes in Women

Pelvic organ prolapse can kink the urethra when severe. Large uterine fibroids may compress the bladder outlet. Post-operative retention following gynecological surgery is common. Vulvar swelling from infection or trauma occasionally causes obstruction.

Medication-Induced Retention

Anticholinergic medications frequently contribute to retention. These include antihistamines such as diphenhydramine, antipsychotics, tricyclic antidepressants, anti-Parkinson medications, and bladder relaxants prescribed for overactive bladder.

Other causative medications include opioid pain medications, sympathomimetic decongestants, muscle relaxants, and certain antihypertensives.

Neurological Causes

Spinal cord injury or compression can disrupt bladder control signals. Cauda equina syndrome requires emergency surgical intervention. Multiple sclerosis, stroke, diabetic neuropathy, and post-operative nerve injury also cause retention.

Precipitating Factors

Common triggers include severe constipation or fecal impaction, cold weather exposure, alcohol intake, general anesthesia, prolonged immobility, and urinary tract infection.

Diagnosis

Clinical Assessment

Diagnosis is often clinical, based on history and examination alone. Patients report sudden inability to void, and examination reveals a palpable, tender bladder. Bedside ultrasound (bladder scan) confirms the diagnosis non-invasively.

A bladder volume exceeding 300-400ml confirms significant retention. Acute presentations commonly show volumes exceeding 1000ml.

Post-Relief Evaluation

After catheterization, clinicians assess the volume drained (often 500-1500ml or more), check kidney function through blood tests, analyze urine for infection, perform prostate examination in men, and arrange further imaging when indicated.

Treatment

Emergency Catheterization

Bladder drainage through urethral catheterization is the primary treatment. A sterile catheter inserted through the urethra provides immediate pain relief. Standard sizes are 14-16 French in men, with larger 18 French catheters used when blood clots are present.

Difficult Catheterization

When standard catheterization fails, options include larger catheters or Tiemann tip (curved) catheters, suprapubic catheter placement through the abdominal wall, cystoscopy with guidewire placement, or urology consultation.

Suprapubic Catheterization

This approach places the catheter directly through the abdominal wall into the bladder. It is used when the urethral route is not possible due to stricture or injury, and is more comfortable for longer-term drainage.

After Catheterization

Immediate Monitoring

Clinicians monitor the volume drained, as decompression hematuria may occur with large volumes. Blood tests assess kidney function, and blood pressure monitoring identifies post-obstructive diuresis—large urine output following relief of obstruction that may require intravenous fluids and electrolyte monitoring.

Trial Without Catheter

After several days with an indwelling catheter, a trial without catheter (TWOC) assesses whether the patient can void independently. Alpha-blocker medications such as tamsulosin or alfuzosin, started 2-3 days before catheter removal, improve success rates. Initial TWOC success rates range from 23-40%.

If TWOC Fails

Options for failed TWOC include a further attempt, extended catheter period, intermittent self-catheterization, prostate surgery (TURP or HoLEP), or long-term catheter management. This situation often leads to overflow incontinence if not properly managed.

Prevention

Preventing recurrence requires addressing the underlying cause—treating BPH with medications or surgery, managing constipation, reviewing medications that may contribute, and treating infection.

Lifestyle measures include avoiding excessive fluid intake at one time, reducing alcohol consumption, emptying the bladder regularly, treating constipation promptly, and avoiding cold exposure.

High-risk patients may benefit from pre-emptive alpha-blocker use before surgery, careful medication selection, and regular prostate monitoring.

Complications

Retention itself can cause bladder overdistension and permanent muscle damage, urinary tract infection, kidney damage if prolonged, and autonomic dysreflexia in patients with spinal cord injury.

Catheterization carries risks of urethral trauma, infection, bleeding, and discomfort. Rapid decompression of a severely distended bladder may cause hematuria, hypotension, or post-obstructive diuresis.

Long-Term Outlook

Following a first episode, 50-70% of patients will experience recurrence without treatment of the underlying cause. Many men ultimately require prostate intervention. TWOC success at first attempt is 23-40%, but improves with alpha-blocker therapy and subsequent attempts.

Surgery becomes necessary after failed TWOC attempts, recurrent retention episodes, complications of long-term catheterization, or by patient preference.

When to Seek Emergency Care

Go to the emergency department if you experience complete inability to urinate for several hours, severe abdominal pain with inability to void, have a known history of retention, cannot urinate after recent surgery, or notice visible abdominal swelling.

Call emergency services immediately if retention occurs with new leg weakness or numbness, loss of bowel control, severe back pain, or signs of autonomic dysreflexia (high blood pressure, headache, sweating) in spinal cord injury patients. These symptoms may indicate cauda equina syndrome or other neurological emergencies requiring immediate intervention.