Is a 7% post-void residual (PVR) urine volume concerning?

Post-Void Residual Urine Volume Assessment: Is 7% Concerning?

A 7% post-void residual (PVR) urine volume is generally not concerning and falls within normal limits for most individuals. 1, 2

Normal PVR Values and Clinical Significance

• PVR values are typically considered in both absolute volume (ml) and as a percentage of bladder capacity 1
• For adolescents, normal PVR is considered:
  • Males: <20 ml (7% of bladder volume) for both 12-14 and 15-18 age groups 2
  • Females: <25 ml (9% of bladder volume) for 12-14 years and <35 ml (10% of bladder volume) for 15-18 years 2
• No specific PVR "cut-point" has been established for clinical decision-making due to test-retest variability 1
• PVR volumes between 200-300 ml (much higher than 7%) are generally considered clinically significant 1, 3

Assessment Considerations

• Due to marked intra-individual variability, a single PVR measurement is not reliable for assessing voiding function 4
• It is recommended to repeat PVR measurement 2-3 times to improve precision, particularly if the first residual urine volume is significant 1, 5
• For children, flow/residual urine measurement should be repeated up to 3 times in the same setting in a well-hydrated child 5
• Bladder over-distention can artificially increase PVR values and should be considered when interpreting results 4

Clinical Implications of Different PVR Values

• PVR of 7% is well below the threshold of concern (typically 10-20% of bladder capacity) 4, 2
• PVR volumes >180 ml have been associated with increased risk of bacteriuria in some studies 6, though this cutoff has been questioned by other research 7
• In children with non-neurogenic lower urinary tract dysfunction, PVR is the most significant non-invasive diagnostic test to predict treatment outcome 8

When to Consider Further Evaluation

• Further investigation may be warranted if:
  • PVR is above the 95th percentile (>30-45 ml or >8-13% of bladder volume, depending on age and gender) 2
  • PVR is consistently elevated across multiple measurements 4
  • There are accompanying symptoms such as recurrent urinary tract infections, incomplete emptying, or voiding difficulties 1
  • There is a history of neurological conditions affecting bladder function 1

Conclusion

A 7% PVR is within normal limits and generally not concerning in the absence of other symptoms or risk factors. However, if there are accompanying urinary symptoms or other risk factors, further evaluation may be warranted despite the normal PVR value 1, 2.