Can we replace the catheter when evaluating urinary residuals?

Abstract

Aims To test the different formulae to calculate the bladder volume using ultrasound; the accuracy of patients hearing/feeling “bubbles” at the end of urodynamics testing as a measure of being empty; and how good we are at estimating PVR using X‐ray at the end of video urodynamics testing. Methods This was a prospective cohort study. Using Sonosite 180 plus, bladder volumes were calculated as, height × width × depth × proportionality constant (0.52, 0.625, 0.65, and 0.7) Patients were asked whether the patient heard or felt “bubbles” at the end of the investigation. Each patient was fluoroscopically screened and the clinician estimated the volume and compared with single‐use catheter volume. Results A total of 85 patients were assessed. All four formulae were significantly correlated. The PC, 0.52, correlated best (r = 0.938, P < 0.001) with no significant difference with the actual volumes ( P = 0.275). The “bubbles test” had a positive predictive value of 93%. A video postvoid residual (PVR) estimation significantly correlated with catheterised bladder volume ( r = 0.842, P < 0.001). There was no significant difference between the estimated and actual bladder volumes ( P = 0.579). Conclusion This study showed that although all four formulae correlated significantly, the PC of 0.52 was the only formula without a significant difference from the actual volume. More work is needed to produce patient individualised PC. Our clinicians were able to accurately estimate the PVR on X‐ray. This study has identified the best formula to accurately estimate bladder volume and that video estimation along with the “bubbles” test can avoid unnecessary intervention.

Three‐dimensional bladder ultrasound for estimation of urine volume in dogs compared with traditional 2‐dimensional ultrasound methods

“…Thus, our study reported a formula described in the human medical literature as being most accurate. 16 When compared to 2 previously reported formulas from the veterinary medical literature, the formula L × W × H × 0.52 resulted in less discrepancy between actual and infused UBV. Because the purpose of our study was to determine how UBV as measured by 3D ultrasound compared to the gold standard of 2D ultrasound measurements, and not that 3D ultrasound was superior to 2D ultrasound, we elected to use the most accurate 2D linear ultrasonographic measurement.…”

“…The formula L × W × H × 0.52 was used to calculate UBV based on a previously published study in people that reported high accuracy. 16 The formulas L × W × H × 0.2π and L × W × ([DL + DT]/2) × 0.625 (DL is depth on longitudinal ultrasound; DT is depth on transverse ultrasound) also were calculated based on previous veterinary studies. 2,15 The specified bladder volume subsequently was estimated using the 3D Verathon BladderScan Prime Plus by small animal internal medicine residents according to manufacturer instructions.…”

“…2,[12][13][14][15] Most recently, use of a simple formula of length (L) × width (W) × height (H) × 0.52 has provided the best estimation of bladder volume in people using 2D ultrasound B-mode images compared to other formulas. 16 Possible disadvantages of 2D ultrasound include extended duration of time to acquire measurements and postimage calculations, which can be time consuming and may increase the risk of calculation errors.…”