Assessment of urinary bladder volume in dogs by use of linear ultrasonographic measurements

OBJECTIVE: To evaluate accuracy of formulas derived from linear ultrasonographic measurements and used in human beings to assess urinary bladder volume as a method of estimating bladder volume in dogs and to test reproducibility of ultrasonographic measurements of linear bladder dimensions. ANIMALS: 64 live dogs (for bladder volume determination) and 31 fresh canine cadavers (for ultrasonographic assessment of reproducibility of measurements). PROCEDURE: Maximal length, longitudinal and transverse depth (DL and DT), and width were measured from the maximal longitudinal and transverse images. Bladder volume was estimated, using 6 formulas, and calculated volumes were compared statistically with the actual volume obtained by catheterization, using paired nonparametric tests. Reproducibility of bladder dimensions was investigated by measuring length, DL, DT, and width 3 times from each image of section. Measurements of depth (DL and DT) also were compared. RESULTS: Calculations of bladder volume from linear dimensions, using a formula described for use in human beings, gave a satisfactory indication of actual bladder volume; the median difference between actual and calculated volumes was only 5 ml. Bladder volume estimations were less accurate when large-volume bladders were measured. Matching between repeated measurements was significant (P < 0.005 for longitudinal bladder length and P < 0.0001 for bladder depth and width). Measurements of DL and DT were significantly (P < 0.01) different, with DL greater than DT. CONCLUSIONS: Ultrasonographic assessment of bladder volume in dogs by application of the formula is sufficiently accurate for most clinical purposes. CLINICAL RELEVANCE: Ultrasonography would be a useful method of estimating bladder volume in dogs with severe obstruction or dysfunctional voiding of urine.