Comparative accuracy of the Lilium α-200 portable ultrasound bladder scanner and conventional transabdominal ultrasonography for postvoid residual urine volume measurement in association with the clinical factors involved in measurement errors.

AIM

We examined the comparative accuracy of the portable ultrasound bladder scanner, Lilium α-200, and conventional ultrasonography (CUS) in bladder volume measurement. We also examined factors that could lead to measurement errors.

METHODS

Postvoid residual (PVR) volume was measured by Lilium α-200 and CUS with catheterized volume as a comparator in 224 consecutive men, of which 109 were also measured for the serially inflated bladder with saline. The measurement accuracy with respect to the actual volume was evaluated by calculating the error volume (EV), % error volume (%EV), and their absolute values. Absolute %EV of ≤20% was designated as nonerror. The measurement of prostate volume, abdominal thickness, and pelvimetry was performed on magnetic resonance images.

RESULTS

PVR volumes measured by CUS are better correlated with actual volumes (r = .779) than those of Lilium α-200 (r = .606). When the measurement accuracy was indicated by absolute values of EV and %EV, CUS provided a more accurate estimate (21 ± 21 ml, 60 ± 42%) than Lilium α-200 (32 ± 45 ml, 91 ± 142%). The frequency of error was significantly increased at lower bladder volumes. Overestimation was associated with larger prostate size for the Lilium α-200, while underestimation was associated with greater bladder flattening for both methods.

CONCLUSION

PVR volumes measured by Lilium α-200 were fairly correlated with actual volumes. However, their relative errors were too large to correctly predict the actual volume. Flattened bladder and a large prostate may hinder accurate measurements. Consequently, Lilium α-200 is not superior to CUS and its feasibility is limited to when the precise measurement is not required.