Reduced voided volume may signal storage symptoms in men with LUTS
Reduced voided volume (VV, <150 mL) on initial uroflowmetry (UFM) may indicate severe storage symptoms in men with lower urinary tract symptoms (LUTS), a new study shows.
A total of 352 men (mean age 63.6 years, mean VV 183.0 mL) with storage symptoms completed a frequency-volume chart (FVC) and were divided into four groups based on VV on initial UFM (<68.8, ≥68.8 to <150, ≥150 to <250, and ≥250 mL). [PLoS One 2019; doi:10.1371/journal.pone.0207208]
Low VV equated to low peak flow rates (4.8 vs 9.1 vs 13.1 vs 19.9 mL/second; p<0.001) and bladder voiding efficiency (73.3 vs 87.7 vs 91.5 vs 95.7 percent; p<0.001). Moreover, participants with low VV had a higher total number of voids (mean, 9.5 vs 9.7 vs 8.3 vs 8.0; p<0.001) and nocturnal voids (mean, 1.7 vs 1.7 vs 1.6 vs 1.1; p=0.007).
Mean daytime urine output (UO) per void increased as VV increased (127.8 vs 142.2 vs 175.1 vs 185.6 mL; p<0.001). “[M]ost examinations including UFM tend to be performed during daytime,” explained the researchers. “Therefore … mean daytime UO per void [may be considered] as a surrogate predictor of VV on repeat UFM.”
On multivariate analysis, older age (B, -3.50, 95 percent confidence interval [CI], -4.89 to -2.10; p<0.001) and decreased functional bladder capacity (B, 0.35, 95 percent CI, 0.25–0.45; p<0.001) emerged as significant variables associated with decreased VV.
“[It is] possible that a greater proportion of older patients did not understand the requirement to sufficiently delay urination before the examination,” the researchers pointed out, hence the decreased VV among elderly participants. Moreover, older age has been associated with detrusor overactivity, which may account for the link between older age and decreased VV. Decreased functional bladder capacity has also been associated with LUTS severity. [Eur Urol 2008;54:419-426; Urology 2001;57:1093-1098]
Therefore, it is important to determine whether the FVC protocols were properly explained to participants to clarify if they clearly understood the requirements for the procedure, noted the researchers. “[We need to evaluate] the degree of understanding and explanation [as this] might be related to the impact of age on decreased VV.”
VV on UFM could be used to appropriately screen patients requiring FVC assessment which, according to the researchers, may be more appropriate than a repeat UFM. A repeat UFM may be warranted following treatment with an antimuscarinic agent and/or a β3-agonist as these reportedly increase VV. [BJU Int 2007;99:85-96] Future studies should evaluate the role of repeat UFM in individuals with decreased VV on initial UFM.
The lack of psychological evaluation could have limited the findings given its reported effect of tolerance on bladder filling, noted the researchers. [Neurourol Urodyn 2006;25:8-12] Furthermore, as the cohort comprised men with severe storage symptoms, the results might be confined to this patient group hence the need for further analysis, they added.
Although the results suggest that initial UFM may not provide adequate information owing to the insufficient VV in men with storage symptoms, the findings underpin the potential of VV on initial UFM to predict storage symptom severity, said the researchers.
Moreover, clinicians should not overlook decreased VV on UFM, said the researchers, adding that this could also be an indicator of overactive bladder (OAB). “It is better to perform a careful clinical assessment to diagnose and treat OAB,” they said.