Are portable bladder scanning and real-time ultrasound accurate measures of bladder volume in postnatal women?

Summary Real-time ultrasound and portable bladder scanners are commonly used instead of catheterisation to determine bladder volumes in postnatal women but it is not known whether these are accurate. Change in bladder volumes measured by ultrasound and portable scanners were compared with actual voided volume (VV) in 100 postnatal women. The VV was on average 41 ml (CI 29 - 54 ml) higher than that measured by ultrasound, and 33 ml (CI 17 - 48 ml) higher than that measured by portable scanners. Portable scanner volumes were 9 ml (CI −8 - 26 ml) higher than those measured by ultrasound. Neither method is an accurate tool for detecting bladder volume in postnatal women.