The validity and reliability of real-time ultrasound estimation of bladder volume in postnatal women

Abstract

Twenty-eight women following forceps delivery were recruited to assess the validity of the ultrasonic estimation of bladder volumes. A further 20 postpartum women with in-dwelling catheters were recruited to assess the reliability of the ultrasound method. The in limit of visualisation of urine in the bladder by ultrasound appeared to be approximately 25 ml. 1 he intraelass correlation coefficients for the bladder volume estimated by ultrasound versus those obtained by urethral catheterisation was 0–98. indicating a high degree of correctness in the ultrasonic measurements (validity). The mean difference between bladder volumes measured by two independent observers for bladder volumes between 40 and 120 ml was + 2–4 ml and the corresponding limits of agreement (mean i s.d.) were -13–6 to ±18–3 ml. The overall intraelass correlation coefficient for bladder volumes independently measured using ultrasound by two observers was 0–99, indicating a high degree of agreement between the two observers (reliability). Real-time ultrasound provides a valid, reliable and non-invasive method of measuring bladder volumes in postpartum women.