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KembaraXtra- Medicine – Acute Urinary Retention
Acute urinary retention (AUR) is defined as the sudden inability to voluntarily pass urine despite a full bladder. It is often painful, although pain may be absent in older adults, patients with neurologic disorders, or those with chronic urinary retention. On physical examination, the bladder is typically distended, palpable, and percussible in the suprapubic region. AUR is distinct from chronic urinary retention, in which patients can void but retain a significant postvoid residual volume and usually do not experience pain.
AUR is one of the most common urologic emergencies, occurring predominantly in aging men, particularly those over 60 years of age, though it can affect individuals of any age and sex. Over a five-year period, approximately 10% of men older than 70 years and nearly one-third of men older than 80 years will experience an episode of AUR. The prevalence is estimated at 40 per 100,000 men and 3 per 100,000 women, with rates increasing as life expectancy rises. No specific genetic predisposition has been identified.
Clinically, patients most often present with acute inability to urinate, suprapubic pain or pressure, and a strong urge to void. Some patients pass only small amounts of urine. Low back pain may occur, and in severe cases, flank pain and costovertebral angle tenderness may develop if high bladder pressures are transmitted to the upper urinary tract. Many patients report worsening lower urinary tract symptoms (LUTS) in the days to weeks preceding AUR, including urgency, nocturia, hesitancy, intermittency, weak stream, stranguria, and incontinence. In patients with cognitive impairment or limited communication, AUR may manifest as agitation, restlessness, confusion, or delirium. Delayed presentation can result in acute kidney injury, electrolyte abnormalities, nausea, and lower extremity edema.
The etiology of AUR is often multifactorial, especially in older adults. Episodes may be spontaneous or precipitated by an identifiable trigger. Spontaneous AUR most commonly results from progressive bladder outlet obstruction, particularly due to benign prostatic hyperplasia (BPH), but may also arise from urethral strictures or pelvic masses. Precipitated AUR occurs when an acute event superimposes on underlying risk factors, such as surgery (especially spinal, orthopedic, or urologic), trauma, excessive alcohol intake, urinary tract infection, constipation, or neurologic insults including stroke or spinal cord injury. Medications are frequent precipitants and include antihistamines, sympathomimetics, anticholinergics, opioids, and anesthetic agents.
Pathophysiologically, urinary retention generally arises from one or more of three mechanisms. These include increased bladder outlet obstruction, as seen with BPH, urethral strictures, malignancy, constipation, or obstructing clots; impaired detrusor muscle innervation or contractility, associated with diabetic neuropathy, spinal cord disease, or prolonged outlet obstruction; and bladder overdistension, which can impair detrusor function following anesthesia or anticholinergic use. In women, causes may include pelvic organ prolapse, fibroid tumors, malignancy, urethral strictures, postpartum vulvar edema, labial fusion, or pelvic masses. Infections such as prostatitis, cystitis, urethritis, genital herpes, and herpes zoster may also precipitate AUR.
The diagnosis of AUR is usually clinical, based on history and physical examination. Workup focuses on identifying the underlying cause and associated complications. A detailed history should assess baseline voiding patterns, prior episodes of retention, recent surgeries or trauma, medication use, neurologic symptoms, and signs of infection. Physical examination includes abdominal assessment for bladder distension, rectal examination to evaluate prostate size, sphincter tone, and fecal impaction, and focused neurologic evaluation to exclude spinal cord or cauda equina pathology. Pelvic examination is essential in women to assess for pelvic organ prolapse or masses.
Laboratory testing typically includes serum electrolytes, blood urea nitrogen, and creatinine to assess renal function, along with urinalysis and urine culture obtained after catheterization. Prostate-specific antigen testing is not recommended in the acute setting, as levels may be falsely elevated following catheter placement. Imaging with bladder ultrasound or bedside bladder scanning is commonly used to confirm urinary retention, though accuracy may be limited by ascites, obesity, pelvic fluid collections, or surgical implants. Additional imaging such as CT, MRI, or renal ultrasound is reserved for suspected pelvic masses, spinal pathology, hydronephrosis, or renal impairment.
Management of AUR requires prompt bladder decompression, most commonly with indwelling urethral catheterization. Coude-tip catheters may facilitate placement in men with prostatic enlargement. Clean intermittent catheterization is an alternative for selected patients with adequate dexterity and cognition. If urethral catheterization is unsuccessful or contraindicated, suprapubic catheter placement is indicated. After decompression, patients should be monitored for postdecompression hematuria and postobstructive diuresis, which may cause significant fluid and electrolyte shifts. Medications that contribute to retention should be discontinued whenever possible.
Following acute management, a voiding trial is typically attempted five to seven days after catheter placement. Alpha-adrenergic blockers improve the likelihood of successful catheter removal in men with BPH and are commonly initiated unless contraindicated. Persistent inability to void after a trial warrants urologic consultation and further evaluation, which may include cystoscopy or urodynamic testing. Patients who fail repeated trials may require intermittent catheterization or long-term catheter management.
Most patients can be safely discharged with close follow-up if renal function is stable and postobstructive diuresis is absent. Hospital admission is indicated for patients with sepsis, complicated urinary tract infection, acute kidney injury, significant electrolyte disturbances, malignancy-related obstruction, hematuria, or suspected spinal cord compression. Urologic referral is required for difficult catheterizations, recurrent AUR, or postoperative cases, while gynecologic referral is necessary when pelvic pathology is identified in women.
Prevention strategies include treating constipation, maintaining mobility, avoiding medications known to precipitate urinary retention, and careful medication selection in patients with BPH. In men with large prostates, long-term use of 5-alpha reductase inhibitors may reduce the risk of future AUR episodes.
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