As usually described, at the lateral margin of the rectus sheath, the lateral muscles
aponeurosis joins themselves in the semilunar line. The external oblique (EO) aponeurosis
constantly passes in front of the rectus muscle (RM), composing the anterior lamina of the
sheath. The internal oblique (IO) aponeurosis splits its fibers in an anterior and a
posterior layer. The anterior layer joins the fibers of the EO in front of RM to constitute
the anterior lamina. But some centimeters below the umbilicus, there is no split in the
fibers, and all the aponeurosis of the IO join the EO and transverse aponeurosis in
constituting the anterior sheath. The transverse muscle aponeurosis also behaves differently
from cranial to caudal. Cranially the fibers constantly remain posterior to the RM and
constitutes the deep layer of the sheath, but at a variable level some centimeters below the
umbilicus, they go anteriorly will all other flat muscle aponeurosis.
During cadaveric dissections and in a careful evaluation of various CT abdominal wall images,
we noted that the IO aponeurosis can join the rectus sheath in two ways: a) splitting its
fibers in an anterior and posterior layer, as classically described, or b) joining only the
posterior rectus sheath without an anterior layer.
To confirm our hypothesis, we design this multicenter cross-sectional observational study.
Data collection:
For each patient, together principal endpoints, following additional variables will be
collected:
Age
Sex
BMI
Previous abdominal surgical procedures (type and date)
Diabetes affection
Number of pregnancies and multiple birth, date of delivery and type of delivery (vaginal
or caesarean section)
CT evaluation
A researcher, trained by an expert radiologist, will evaluate the axial image of abdominal
standard CT to identify and record:
the internal oblique aponeurosis insertion in both side: classical double (anterior and
posterior) insertion or only posterior insertion
The inter-recti distance at three regions, including supraumbilical (4,5 cm above the
umbilicus), periumbilical and subumbilical (4.5 cm below the umbilicus)
The thickness and width of both rectus muscles
The distance between lateral edge of the rectus muscle and the medial edge of the
internal oblique muscle
The distance between lateral edge of the rectus muscle and the medial edge of the
external oblique muscle
The distance between lateral edge of the rectus muscle and the medial edge of the
transverse muscle
Presence of abdominal wall hernia, if any
Definition and classification of DRA According Rath et al. (13) proposal, for subjects
younger than 45 years, DRA will be defined as a separation of the two recti more than 1.0 cm
above the umbilicus, 2.7 cm at the periumbilicus and 0.9 cm below the umbilicus; for subjects
over 45 years, the corresponding values will be 1.5 cm, 2.7 cm and 1.4 cm, respectively. The
presence of an inter-recti distance superior to the cut off value in two or three regions
(supraumbilical, umbilical and subumbilical) in the same patient will be described as DRA.
Width of the DRA will be defined according Ranney (15) classification: an IRD < 3 cm will be
labeled mild diastasis, 3-5 cm IRD moderate diastasis and more than 5 cm severe diastasis.