US scans were performed with high-frequency, broad-band linear transducers. Transducer frequency could be adapted according to the thickness of the subcutaneous layer, but it was typically 10 MHz.

Patients were placed in the supine decubitus, with the head slightly extended above a pillow, the upper limbs aligned to the trunk and the knees slightly flexed.

Measurements were obtained at rest, in a neutral moment immediately after an expiration. We accurately avoided pressing excessively on the abdominal surface with this transducer, to avoid pressure-related contraction reflexes.

The typical level of the transverse scan of the abdominal wall was 3 cm above the navel and 2 cm below the navel, but the entire of the midline was checked to identify the exact pattern of diastasis.

All measures were taken three times and the mean value was recorded. Diastasis was defined as a margin-to-margin distance between the medial border of the two rectus muscles more than 20 mm.

In the case of a diastasis exceeding 4 cm we employed trapezoid field-of-view scans to measure, while in the case of diastasis above 5 cm we employed real-time, extended field-of-view reconstructions.

In our practice we also routinely check the abdominal wall midline, both at rest and during the Valsalva manoeuvre, to rule out any concomitant hernia.