Inter-rater reliability and variability of ultrasound measurements of abdominal muscles and fasciae thickness.

Ultrasound (US) imaging is being increasingly used by Physical and Rehabilitation Medicine (PRM) specialists to measure the thickness of abdominal muscles. The current study set out to assess the inter-rater reliability of US measurements of the thickness of the abdominal muscles/fasciae. Three raters (1 = orthopedic specialist, expert on fasciae; 2 = PRM resident; 3 = PRM specialist) with different levels of US training examined the abdominal muscles and fasciae of a healthy volunteer under supine resting and dynamic conditions following a standard US protocol. The probe was positioned along the right lateral abdominal wall at the height of the 12th rib: (1) above the umbilicus at the linea alba, (2) to the side of and approximately 2 cm from the umbilicus, (3) along the mammillary line, and (4) along the anterior axillary line. Each rater measured 17 anatomical structures six times during two sessions. The relative error of the measurements (intra-rater variability) was slightly higher for the fasciae than for the muscles, and during the dynamic condition than the resting condition. Inter-rater reliability was good under both conditions for the fasciae (Intraclass Correlation Coefficient = ICC = 0.83) and excellent for the muscles (ICC = 0.99). Knowledge of the fascial anatomy of the abdominal wall is essential for accurate ultrasound examinations and for improving reliability. These findings confirm that US imaging is a reliable, non-invasive, cost-effective instrument for evaluating the abdominal muscles/fasciae. Clin. Anat. 32:948-960, 2019.