In normal individuals, there are two longitudinal major vessels located on either side of the frenulum under the tongue, known as the sublingual vessels (舌下络脉, jié xià luò mài). They are also referred to as “stasis vessels” (瘀络, yū luò). The mucous membrane under the tongue forms a prominent fold that connects to the floor of the mouth, called the frenulum (舌系带, jié xì dài). On either side of the frenulum, through the mucosa, the sublingual veins (舌静脉, jié jìng mài) can be seen in a light blue color. In normal individuals, the sublingual vessels are faintly visible, with a diameter not exceeding 2.7 cm and a length not exceeding three-fifths of the line connecting the tip of the tongue to the sublingual tubercle. The color is dark red, and the vessels are neither engorged, constricted, twisted, nor proliferated, arranged in an orderly manner. The vast majority are single branches, with very few instances of double branches.
The observation of the sublingual vessels mainly involves examining their length, shape, color, thickness, and the changes in the small blood vessels under the tongue.
The method for observing the sublingual vessels is as follows: have the patient open their mouth, lift the tongue towards the palate, lightly touch the tip of the tongue to the palate without excessive force, allowing the tongue to relax naturally, thus fully exposing the sublingual vessels. First, observe the length, thickness, and color of the major vessels on either side of the frenulum for any abnormal changes such as engorgement or curvature, and then observe the surrounding small vessels for any abnormalities in color or shape.
Abnormalities in the sublingual vessels and their clinical significance:
If the sublingual vessels are short and thin, and the surrounding small vessels are not prominent, with a pale tongue color, this often indicates deficiency of Qi and blood (气血不足, qì xuè bù zú), leading to insufficient filling of the vessels.
If the sublingual vessels are thick and engorged, or appear in shades of blue-purple, dark red, or purple-black, or if the small vessels under the tongue appear as a dark red or purple network, or if the sublingual vessels are varicose with nodules of varying sizes resembling purple beads, these are all signs of blood stasis (血瘀, xuè yū). The causes may include Qi stagnation, cold congealing, heat accumulation, phlegm-dampness, Qi deficiency, or Yang deficiency, and should be analyzed in conjunction with other symptoms.
Changes in the sublingual vessels may sometimes precede changes in tongue color; therefore, the sublingual vessels are an important basis for analyzing the circulation of Qi and blood.
The diagnostic method for the sublingual vessels refers to the examination of their color, shape, and fullness to assist in disease judgment. Normal sublingual vessels are faintly visible under the tongue, with a dark red color, soft shape, and no curvature or constriction, not exceeding one-third of the sublingual area. Therefore, when examining for blood stasis, one should first observe the sublingual vessels.
The pathological changes of the sublingual vessels mainly manifest in color and shape. If the color of the vessels is blue-purple, and their shape is thick and long or engorged, this suggests Qi stagnation and blood stasis, or phlegm and blood obstruction; if the color is pale purple, and the shape is thick or engorged, this suggests cold evil stagnation or Qi deficiency and blood stasis; if the color is purple-red and the shape is engorged, this suggests heat accumulation and blood stagnation; if the color is pale red or light blue, and the shape is thin, this suggests weakness of the righteous Qi. Therefore, changes in the sublingual vessels mainly indicate the presence of blood stasis, confirming whether the stasis is due to Qi stagnation, cold congealing, Qi deficiency, or heat accumulation based on their colors of blue-purple, pale purple, or purple-red.
The “stasis vessels” categorize the degree of abnormality of the sublingual vessels into four levels: 0 degree, I degree, II degree, and III degree.
0 degree indicates that the two sublingual veins are faintly visible, with a main trunk diameter of less than 2.6 mm, a length not exceeding the frenulum endpoint, and the entire sublingual vein is neither twisted nor engorged;
I degree (++) indicates that the main trunk is full, with a diameter not exceeding 2.6 mm, a length not exceeding half the distance from the frenulum endpoint to the tip of the tongue, with slight curvature;
II degree (+++) indicates that the main trunk is full, with a diameter exceeding 2.6 mm, a length exceeding three-fifths of the distance from the frenulum endpoint to the tip of the tongue, with slight curvature; II degree (+++) indicates that there is obstruction of Qi and blood in the body.
III degree (++++), indicates that the main trunk is full, significantly engorged, with a diameter exceeding 2.6 mm, a length exceeding three-fifths of the distance from the frenulum endpoint to the tip of the tongue or reaching the tip of the tongue, with coarse branch-like extensions or caviar-like protrusions. III degree (++++), indicates the presence of early tumors in the body.
