What amount of post-void residual (PVR) urine and what size of prostate are considered significant and enlarged?

Significant Post-Void Residual Urine Volume and Prostate Size

A post-void residual (PVR) urine volume greater than 200-300 mL is considered clinically significant, while a prostate volume greater than 30 mL is generally considered enlarged. 1, 2

Post-Void Residual Urine Volume

Clinical Significance Thresholds

• PVR volumes between 200-300 mL may indicate significant bladder dysfunction and predict a less favorable response to treatment 1
• PVR of 350 mL or greater strongly indicates bladder dysfunction and may herald disease progression, particularly in BPH 2, 1
• A PVR threshold of 180 mL has been identified as having the best sensitivity and specificity for predicting bacteriuria in asymptomatic men (positive predictive value of 87.0%) 3
• No specific PVR "cut-point" has been established for clinical decision-making due to test-retest variability, but values above 200-300 mL warrant attention 1, 2

Measurement Considerations

• Due to marked intra-individual variability, PVR measurement should be repeated to improve precision 2, 1
• Transabdominal ultrasonography is the preferred non-invasive method for determining PVR 2
• PVR measurements are considered valid when voided volumes are 150 mL or greater 4

Clinical Implications

• Men with PVR of 400 mL or greater have a significantly higher rate (75%) of requiring surgical intervention or catheterization compared to those with PVR of 0-199 mL (4%) 4
• PVR between 0-300 mL does not predict response to medical therapy for BPH 2
• No level of residual urine, in and of itself, mandates invasive therapy for BPH, but should be considered in the context of other clinical factors 2
• Bladder voiding efficiency (calculated as voided volume divided by voided volume plus PVR) below 75% predicts poorer surgical outcomes after prostate procedures 5

Prostate Size

Significant Enlargement

• A prostate volume greater than 30 mL is generally considered enlarged 6
• Men with prostate volumes greater than 30 mL have 2.5 times greater odds of having PVR greater than 50 mL 6
• Prostate size assessment is important when considering certain treatments (e.g., hormonal therapy, thermotherapy, stents, transurethral incision of the prostate) 2

Measurement Methods

• Transabdominal or transrectal ultrasound are the preferred methods for assessing prostate size, shape, and configuration 2
• Transrectal ultrasonography is the method of choice when elevated PSA is present to evaluate the prostate and guide biopsies if needed 2

Clinical Implications

• Men with enlarged prostate volume (>30 mL) or PVR greater than 50 mL are approximately 3 times more likely to experience acute urinary retention requiring catheterization during 3-4 years of follow-up 6
• Prostate size correlates significantly with PVR (rs = 0.24, p <0.001) 6
• Larger glands may require different treatment approaches than smaller glands in men with similar symptoms 2

Clinical Decision-Making

• PVR measurement is considered an optional test in the initial evaluation of men with lower urinary tract symptoms (LUTS) but becomes more important in those considering invasive therapy 2
• Men with maximum flow rate (Qmax) less than 10 mL/sec are more likely to have urodynamic obstruction and may benefit more from surgical intervention 2
• Chronic urinary retention is often defined as either a PVR of >300 mL in men who are voiding, or >1000 mL in men who are unable to void 7
• Conservative management may be appropriate for most older men with incidentally found elevated PVR of up to 400 mL 4