The arcuate line of the rectus sheath--does it exist?

The lower halves of the anterior abdominal wall of 40 human specimens of both sexes and various ages were studied. The anatomical features seen were widely variable and quite different from the conventional picture. The fibres of the posterior lamina of the internal oblique and transversus abdominis aponeuroses gradually shift from the posterior to the anterior rectus sheath starting from the level of the umbilicus down to the level of the symphysis pubis. Thus, these anterior laminae gradually increase in thickness at the expense of their posterior laminae. As a result, the arcuate line is absent. Instead, one or more of the following features could be seen: (i) A gradually thinned out but complete PRS. (ii) An ill-defined or double arcuate line. (iii) A complete PRS of nearly normal thickness. (iv) A dense well-formed transverse aponeurotic band crossing from one side to the other at the level of the umbilicus, symphysis pubis or midway between them.