Acute Urinary Retention (AUR) is the Term for Inability to Urinate Due to Prostate Enlargement
Acute urinary retention (AUR) is the medical term for the inability to urinate due to prostate enlargement caused by benign prostatic hyperplasia (BPH). 1, 2
Understanding AUR in BPH
- AUR is a significant complication of BPH where patients experience a sudden and painful inability to pass urine despite having a full bladder 2
- The incidence of AUR increases with age, from 6.8 episodes per 1,000 patient years in the overall population to 34.7 episodes in men aged 70 and older 1, 2
- AUR typically requires emergency catheterization to relieve the obstruction and associated pain 3
Pathophysiology of AUR in BPH
BPH contributes to urinary obstruction through two primary mechanisms 2:
- Static component: Direct bladder outlet obstruction from enlarged prostatic tissue
- Dynamic component: Increased smooth muscle tone and resistance within the enlarged gland
The underlying cause is the proliferation of glandular epithelial tissue, smooth muscle, and connective tissue within the prostatic transition zone 1
This enlargement creates pressure on the urethra, increasing resistance to urine flow and eventually leading to complete obstruction in AUR 4
Risk Factors for AUR
- Age is the primary risk factor, with BPH prevalence reaching 60% by age 60 and 80% by age 80 2
- Larger prostate size (>30cc) significantly increases the risk of AUR 1, 3
- Severe lower urinary tract symptoms (LUTS) are predictive of future AUR 5
- Untreated BPH with progressive symptoms increases the likelihood of developing AUR 6
Warning Signs Before AUR
Progressive worsening of voiding symptoms including 5:
- Weak urinary stream
- Hesitancy (difficulty initiating urination)
- Intermittency (stopping and starting during urination)
- Straining to urinate
- Sensation of incomplete emptying
High post-void residual (PVR) urine volumes indicate impending AUR 5, 7
Clinical Implications
- AUR represents a urological emergency requiring prompt intervention 2
- In the PLESS trial (Proscar Long-term Efficacy and Safety Study), untreated BPH led to AUR in 6.6% of patients in the placebo group compared to 2.8% in the treatment group over 4 years 3
- AUR often necessitates surgical intervention if medical management fails 3
Prevention of AUR
- Early medical intervention with alpha-blockers (e.g., tamsulosin) can reduce the risk of AUR by relaxing smooth muscle in the prostate and bladder neck 8
- 5-alpha reductase inhibitors (e.g., finasteride) can decrease prostate volume by 17.9% over 4 years, reducing AUR risk by 57% compared to placebo 3
- Combination therapy with both medication classes may provide additive benefits in preventing AUR in high-risk patients 3, 9