Acute Urinary Retention

Nephrology

Overview Acute urinary retention (AUR) is the inability to voluntarily pass urine. It is the most common urologic emergency. In men, AUR is most often secondary to benign prostatic hyperplasia. Acute urinary retention is rare in women.

Pathogenesis

Outflow obstruction Mechanical obstruction refers to a physical narrowing of the urethral channel
Neurological impairment AUR may develop secondary to the interruption of the sensory or motor nerve supply to the detrusor muscle
Inefficient detrusor muscle Inefficient detrusor muscle when a precipitating event results in an acute distended bladder

CLASSIFICATION OF URINARY RETENTION
Obstruction	Benign prostatic hyperplasia (BPH). Other causes of outflow obstruction in men include constipation, cancer (prostate or bladder), urethral stricture, urolithiasis, phimosis, or paraphimosis
Neurological Disease	Spinal cord injuries from trauma, infarct or demyelination, epidural abscess and epidural metastasis, Guillain-Barré syndrome, diabetic neuropathy, and stroke
Medications	Anticholinergic and sympathomimetic drugs
Infections	Infections may lead to AUR in the setting of inflammation that causes obstruction. For example, an acutely-inflamed prostate gland from acute prostatitis
Trauma	Trauma to the pelvis, urethra, or penis

COMMON CAUSES OF ACUTE URINARY RETENTION BASED ON GENDER
	Condition	History	Examination
MEN	Prostate Cancer	Weight loss, constitutional signs and symptoms	DRE: enlarged nodular (hard) prostate
	Benign Prostatic Hyperplasia	Nocturia, frequency, polyuria, hestitency, double voiding	DRE: enlarged firm, non-tender, non-nodular prostate
	Acute Prosatitis	Dysuria, Fever	DRE: tender, boggy prostate
	Phimosis, Paraphimosis	Pain and swelling of foreskin or penis	Oedema of penis with nonretractable foreskin
WOMEN	Vulvovaginititis	Vaginal Discharge, itch, dysuria	Vaginal discharge, inflamed genital area
	Cystocele	Feeling of pelvic heaviness or fullness, noticeable bulge from the vagina.	Notable bulge on the anterior vaginal wall
	Pelvic mass (fibroids, gynaecological malignancy)	Feeling of pelvic heaviness or fullness, dysmenorrhea, menorrhagia	Palpable uterine mass
BOTH GENDERs	Urinary Tract Infection	Dysuria, haematuria, groin/loin/back pain, genital rash	Supracpubic tenderness, urethral discharge, genital rash
	Bladder Tumour	Painless haematuria with clots	-
	Neurogenic Bladder	Diagnosed neurological disease	Other generalised or focal neurologic deficits

Approach

History
- Presentin history
- Medication (alcohol, antihistamine, anticholinergics, tricyclics)

Rememeber Faecal impaction in the elderly may be a cause of urinary retention

Examination
- General observation
- Bladder percussion
- Bladder palpation
- Flank palpation
- PR examination
- Spinal injury - neurological exam

Rememeber Digital rectal examination is mandatory in the patient with new retention

Investigation and Diagnosis
- FBC
- Urine MSU
- EUC
- Chest X-ray - pulmonary oedema (chronic kidney failure) and possible tumour
- Bladder ultrasound
  - Confirm bladder size
  - Dilated upper urinary tract
  - Pregnant uterus
- Urethrography
- PSA
- Cystoscopy
- Urodynamics