The prospective observation with post-hoc analysis of 171 consecutive colorectal cancer patients was performed. In all patients 16-item ERAS protocol was applied.
Contrast-enhanced CT scan was performed preoperatively. From each scan one CT image at the level of L3 vertebra was transferred in Digital Imaging and Communications in Medicine format (DICOM) and anonymised. Firstly, the threshold range between -29 and +150 Hounsfield units was set to semi-automatically outline muscle areas, - 150 to - 50 was used for visceral adipose tissue areas, and -190 to -30 was used for subcutaneous and intermuscular adipose tissue areas. Secondly, the software calculated the surface area (cm2) of each tissue. The L3 skeletal muscle area (rectus abdominis, external and internal obliques, transversus abdominis, quadratus lumborum, psoas, erector spinae) normalized for patient height was used to calculate skeletal muscle index (SMI) (cm2/m2).
According to Martin et al. sarcopenia was defined as a SMI \<41 cm2/m2 in women, \<43 cm2/m2 in men with a BMI \<25 kg/m2, and \<53 cm2/m2 in men with a BMI \>25 kg/m2 (10). To assess for myosteatosis the mean radiodensity of a L3 psoas muscle was measured. The cut-off for patients with BMI \<25 kg/m2 was \<41 Hounsfield units and \<33 Hounsfield units for patients with BMI ≥25 kg/m2.
For the purposes of further analysis the entire group of patients was divided into subgroups depending on the presence of sarcopenia or myosteatosis.
