Accuracy of preoperative ultrasound measurement of rectus diastasis compared to in vivo findings: a comparative study

Introduction: In July 2022 a new Medicare Benefits Schedule (MBS) item number 30175 was created for a radical abdominoplasty with rectus diastasis repair. To qualify for this benefit and attain a significant reduction in their out-of-pocket surgical cost, patients are required to undergo preoperative radiological assessment of their rectus diastasis with a measured inter-rectal distance (IRD) of 3 cm or more. This study examines the relationship between preoperative radiological evaluation of the IRD and intraoperative measurements for patients undergoing abdominal wall procedures with rectus diastasis repair. Methods: This study included patients aged 18 years and older who underwent abdominal skin procedures with rectus diastasis repair from March 2022 to April 2024. Preoperative ultrasound assessed the IRD, defined as the distance between the medial edges of the rectus abdominus muscle, with maximum IRD values recorded. Intraoperative IRD measurements were taken at the reported radiological IRD locations using a sterile ruler. Paired t-tests were employed for statistical analysis. Results: The study involved 27 female patients with a median age of 52 years. Preoperative ultrasound consistently underestimated the IRD (mean = 31.9 mm, SD = 9.6) compared to intraoperative measurements (mean = 39.4 mm, SD = 10.2), with a mean difference of 7.43 mm (p = 0.003). Discussion: Ultrasound is a reliable diagnostic tool, however, its accuracy in measuring IRD has come under scrutiny in the wake of the introduction of MBS item number 30175. Speculative explanations for the discrepancy between radiological and intraoperative measurements are discussed including measurement bias, anatomical factors and mechanical factors. Conclusion: Preoperative ultrasound significantly underestimates the IRD compared to in vivo findings in patients with rectus diastasis. Surgeons should anticipate finding larger in vivo diastasis compared to preoperative radiological values.