Acute Urinary Retention

Acute urinary retention (AUR) is commonly encountered condition in the emergency department. It is the inability to void voluntarily despite a distended bladder that often leads to agitation or altered mental status in the elderly who are on several medications. Classical patient with AUR is an elderly man with BPH. 

Hypertension or tachycardia may be transient and may resolve after bladder decompression. 

Higher Centres and Receptors involved in Micturation
Micturition involves coordination of high cortical neurologic (sympathetic, parasympathetic, and somatic) and muscular (detrusor and sphincter smooth muscle) functions.

Urinary Retention requires both relaxation of the detrusor muscle (through β-adrenergic stimulation and parasympathetic inhibition) and contraction of the bladder neck and internal sphincter (through α-adrenergic stimulation). In contrast, Urination requires contraction of bladder detrusor muscle (by cholinergic muscarinic receptors) and relaxation of both the internal sphincter of the bladder neck and the urethral sphincter (throughα-adrenergic inhibition). 

Common Causes of Urinary Retention

• BPH
• Prostate Cancer, Phimosis, Paraphimosis
• Meatal Stenosis
• Prostatitis
• Medications (Anticholinergics, Antihistaminics, Antipsychotics, BZDs etc.)

Females presenting with AUR should undergo neurologic examination and a pelvic examination to detect possible inflammatory lesions or pelvic masses. 

AUR is a clinical diagnosis but bedside US can be used as an adjunct. Prolonged obstruction may result in impaired renal function and electrolyte imbalance. Thus, renal function studies and Potassium should be checked for those with prolonged retention. Formal abdominal imaging and urodynamic studies can be deferred as an out-patient if the patient appears clinically well. 

A thorough history is required to find the cause/precipitant of Urinary Retention

ED management is limited to bladder decompression with urethral catheterization or suprapubic catheterization (if urethral cath fails). Alpha-blockers can be prescribed during discharge to relax the uretheral muscles. 


Disposition and Indications for admission

Admit in case of:

• Significant Post Renal Failure
• Post Obstructive Diuresis
• Frank Hematuria
• Clot Retention 
• Sepsis

Majority of patients with AUR are discharged home after bladder decompression and Urology Clinic review. It is paramount to educate them about catheter care to avoid accidental displacement/removal of the catheter leading to urethral injury. Reg flags include - fever, abdominal pain, catheter blockage, or penile pain. Tho who complain of a sense of urgency despite being on foleys can be treated with oxybutynin, 2.5 milligrams twice/thrice daily. 

Posted by:

              

     Lakshay Chanana

     

     Speciality Doctor

     Northwick Park Hospital

     Department of Emergency Medicine

     England

     @EMDidactic