Infrared Illumination and Subcutaneous Venous Network: Can it be of Help for the Study of CEAP C₁ Limbs?

Abstract

The subcutaneous venous network (SVN) is difficult to see with the naked eye. Near infrared illumination (NIr-I) claims to improve this. The aims of this observational study were to investigate whether there are differences between the different methods; to quantify the length and diameter of SVNs; and to confirm if they differ between C_0A and C₁ CEAP limbs. In total, 4 796 images, half of them from the visible spectrum (VS) and the other half from the nearninfrared spectrum (NIrS), belonging to 109 females (C_0A: n = 50; C₁ CEAP: n = 59) were used to establish the morphological characteristics of the SVN by visual analysis. With Photoshop CS4, SVN diameters and lengths were obtained by digital analysis of 3 052 images, once the images of whole extremities were excluded. On NIr-I, the diameters, trajectories, and colouration of SVNs of C₁ limbs appeared more irregular than SVNs of C_0A limbs. Compared with the VS images, NIr-I allowed visualisation of a greater length of the SVN in both groups (p < .010). This capacity varied from 2.6 ± 0.9 times (C₁) to 16.2 ± 11.9 (C_0A). While the SVN length seen in the VS images from C₁ limbs was greater than observed in C_0A limbs (p < .001), differences between NIr-I images only existed in the lateral part of the lower leg (p = .016). With NIr-I, the median diameter of the C₁ CEAP SVN veins was 5.8 mm (interquartile range [IQR] 4.3-7.5 mm), while the median diameter in C_0A SVN limbs was 2.6 mm (IQR 2.0-3.6 mm) (p < .001). The NIr-I reveals the characteristics of the SVN better than the naked eye. Further studies are required to determine the significance of the changes in the SVN in C_0A and C₁ limbs, and the factors causing them.