Prediction of operation time for laparoscopic myomectomy by ultrasound measurements

Abstract

This study aimed to develop a regression-based prediction equation for operation time for laparoscopic myomectomy (LM) using ultrasound measurement. Patients who were to undergo laparoscopic myomectomy from March 2003 to December 2005 were enrolled prospectively in a tertiary institution. Ultrasound was performed before operation. The myoma weights were calculated and converted into mass units (g) by an assumed smooth muscle density of 1.04 g/cm³. Myomas were weighed immediately after operation, and the correlation between these two weights was assessed by linear regression and limits of agreement. A multivariate linear regression model was fitted to the ultrasound parameters and clinical variables to predict operation time. Of 109 patients, 203 myomas were removed laparoscopically with a mean ultrasound-measured myoma weight of 137.9 (100.7) g, a diameter of the dominant myoma of 6.30 (1.92) cm, and an operation time of 125 (41) min. Strong correlations were observed between the ultrasound-measured and operated myoma weights. A predictive model, in which operation time = 0.14 × ultrasound-measured myoma weight + 1.68 × BMI + 5.21 × operated myoma number + 0.06 × (ultrasound-measured myoma weight × operated myoma number) + 43.97, was developed. Operation time was significantly related to the myoma weight measured by ultrasound. The ultrasound-derived prediction equation is valid and reliable in predicting operation time for LM.