Validity of Inter-rectus Distance Measurement in Postpartum Women Using Extended Field-of-View Ultrasound Imaging Techniques.

STUDY DESIGN: Reliability and validity study.

OBJECTIVES: To investigate the criterion-related validity and reliability of inter-rectus distance (IRD) measurement using extended field-of-view (FOV) techniques during ultrasound imaging (USI) in parous women.

BACKGROUND: Ultrasound imaging is the gold standard for noninvasive IRD measurement in parous women when investigating diastasis recti; however, its use is limited when IRD is large. Extended FOV techniques (panoramic USI or using acoustic standoff pads) allow complete visualization of the linea alba when the IRD is large and conventional imaging is not sufficient; however, the validity of using these techniques has never been investigated.

METHODS: Two-dimensional ultrasound images were acquired at the superior umbilical border from 21 women using conventional USI, panoramic USI, and a standoff pad. Five images were captured using each method. Inter-rectus distance was measured offline. Criterion-related validity was investigated using repeated-measures analyses of variance to test for bias, and linear regression models, Pearson correlation coefficients (r), and intraclass correlation coefficients (ICCs) to assess agreement. Standard error of the measurement for each extended FOV technique was calculated. The between-trial reliability of each technique was determined using ICCs.

RESULTS: Inter-rectus distance from images acquired using extended FOV techniques did not differ from values acquired using conventional USI (P = .441). Images acquired using extended FOV techniques were highly correlated with those acquired using conventional imaging (r>0.95, P<.0001). The standard error of the measurement of each extended FOV technique was 0.17 to 0.18 cm. The between-trial reliability of all techniques was excellent (ICC(3,1)>0.90).

CONCLUSION: Panoramic USI and acoustic standoff pads are valid methods of increasing FOV to measure IRD. In this study, USI measurements were limited to IRDs of less than or equal to 3 finger widths, based on palpation.