According to the CEAP classification updated in 2020, varicose veins are classified into telangiectasia, reticular vein, and varicose veins depending on the size of the vein [1]. Telangiectasias (subdermal spider veins, <1 mm in size) belong to Class C1. Reticular veins (subdermal veins between 1 and <3 mm in diameter) belong to Class C1. Superficial or saphenous veins dilated more than 3 mm are classified as C2, and the diameter could be used to distinguish C2 of superficial veins from Class C1 of superficial veins. C2 or higher class is usually included in chronic venous disease (CVD), and chronic venous insufficiency (CVI) include diseases more than Class C3. CVI is a more advanced form of CVD and refers to a condition accompanied by functional abnormalities in the venous system. According to CEAP classification, the progression of venous disease from C0 to C6 is mainly classified as worsening clinical symptoms. Vein size appears to be less important in Class C2 and above. The progression of venous disease is very diverse. Symptoms may be mild in advanced forms, or clinical symptoms may appear even without visible varicose veins. In this review, we want to know what is the clinical consideration of vein diameter in the patients with CVD.

The current hypothesis for venous pathophysiology is that valvular abnormalities and venous dilation lead to blood regurgitation and venous hypertension. Due to venous hypertension, capillary permeability increases, tissue hypoxia and secretion of inflammatory substances increase, and as the disease progresses, complications such as skin changes and ulcers are accompanied [2]. Clinically, venous hypertension is an important mechanism in the progression of the disease, and expansion of the size of veins can be seen as a process by which venous hypertension occurs.

The reason the guidelines and appropriate use criteria (AUC) recommend treatment in symptomatic patients is because treatment is necessary when symptoms occur due to venous hypertension [3-5]. There are no longer guidelines recommending treatment by diameter. Even if reflux is limited to below the knees, treatment for venous hypertension should be necessary if it is accompanied by edema and ulcers.

Nevertheless, studies on vein diameter have been conducted to predict reflux in varicose veins. There was a significant difference in diameter depending on the presence or absence of reflux, but it seems difficult to provide an accurate cutoff value for predicting venous reflux [6].

In varicose veins, venous hypertension occurs due to valve insufficiency and shunt formation. A shunt is defined as when different structures are connected. Leg venous network have normal blood flow from the skin to the deep system and from bottom to top, but if normal venous blood flow is not maintained due to valve abnormalities, reflux occurs and venous dilatation occurs. The diameter of the vein will expand as pressure increases [7]. This is a reversible phenomenon, and as pressure decreases, the diameter also could decrease. At low pressure, the radius of veins is reduced to an oval shape, and as the pressure gradually increases, they change into a round shape. When the pressure begins to exceed 20 mmHg, the round veins stretch and become even larger in diameter.

When measuring greater saphenous vein (GSV) diameter, proximal thigh (PT) diameter is known to be more reliable than saphenofemoral junction (SFJ) diameter [8]. At that site, GSV is cylindrical shape and a largely devoid of joining branches. So, this site is well accessible and measurement can be taken reliably. In contrast, the curvature of the SFJ at inguinal area is prevent to ultrasound probe to be placed perpendicular to the vein exactly. According to Mendoza’s study [8], the GSV diameter of PT site was about 2 to 6 mm. In cases where the diameter of PT site was 3.7 mm or less, reflux was reported to be present in 3% of patients. Vein diameter was on average 3.4 mm (p<0.001) larger in SFJ and 2.6 mm (p<0.001) larger in PT compared to those with reflux. In patients with reflux, the distribution of GSV diameter was wide regardless of CEAP class. CVD progresses regardless of the diameter.

This can be explained by the hydrostatic paradox. Because hydrostatic pressure is affected by fluid density, gravity, and height. The same hydrostatic pressure is measured if the height is the same regardless of the area of the water column. This means that venous hypertension can occur due to deep veins and shunts regardless of the diameter of the varicose veins. Dr. Mendosa also says that the shape of veins is influenced by shunt formation and deep vein reflux [8].

Ultimately, elevated AVP is important consideration in patients with varicose veins. Normal AVP is around 10 to 30 mmHg, and if it is over 45 mmHg, it is considered severe venous hypertension. Plasma exchange is maintained by the balance between hydrostatic pressure and oncotic pressure. The interstitial pressure can be maintained up to 42 mmHg, but if interstitial pressure is increased, lymphatic blood flow may be impaired and edema may occur. The target of varicose vein surgery is physically enlarged blood vessels, but ultimately, the purpose of surgery is removal of venous hypertension to release lymphatic blood flow.

Venous pressure can be measured directly with vein puncture, but air-phlethysmography (APG) could also be used indirectly. Among APG parameter, residual volume fraction (RVF) shows good correlation with AVP and can generally be used as a replacement for AVP [9]. When treating varicose veins, symptoms may be improved by lowering AVP to below 40 mmHg at the ankle with the goal of improving AVP. If AVP is over 40 mmHg after treatment of AK GSV alone, AVP may increase due to incompetent perforator veins, etc. in BK GSV. It would be a good idea to consider this when deciding on treatment. If there is no change in AVP or diameter, treatment such as incompetent perforator vein or phlebectomy should be considered.

SR for the large saphenous vein was recently reported [10]. If diameter was 10 mm or more, it was classified as a larger saphenous vein, and endothermal ablation was recommended as a treatment method. When applying thermal ablation, there is no upper diameter limit, but energy modification is required for effective treatment. And as the diameter increases, the increase in endothermal heat induced thrombosis (EHIT) must also be considered. The european society for vascular surgery (ESVS) guideline used 12 mm as the standard and also recommended endovenous thermal ablation [5]. The SVS guideline states that endovenous laser ablation (EVLA) or radiofrequency ablation (RFA) should be performed based on 10 mm [4].

It is unclear whether technical success can be achieved by adjusting the cyanoacrylate dose according to vein size. Kubat, et al. compared stripping vs RFA vs cyanoacrylate vs EVLA at 2 different wavelengths at 2021, in Turkey [11]. Total 671 patients were followed up for 12 months. The GSV diameter was 10 mm and above. Statistically significant higher recurrence rates in the cyanoacrylate (12/79, 15.2%) and 980 nm EVLA (22/148, 14.6%) groups, compared with stripping (3/86, 3.2%), 1,470 nm EVLA (6/109, 5.5%), RFA 15/249 (5.7%) at 12 months. Occlusion rate was lower in cyanoacrylate which was 84.8%, following 88.1% in 980 nm EVLA and >95% in 1,470 nm EVLA or RFA (p=0.001).

Non randomized prospective was conducted for cyanoacylate in 29 patients with 57 varicose veins (VVs) in Hong Kong [12]. FU period was 12 months. Closure rates of GSV ≥8 mm was 90.9%, 90.9%, 68.2%, and 34.1% at postoperative 1 week, 1 month, 6 months, and 12 months, respectively (log rank test, p=0.006).

There is limited evidence to support the use of MOCA for the treatment of veins larger than 10 mm. In the initial clinical trial by Elias et al., veins exceeding 12 mm in diameter were excluded considering that the rotating wire of the device was 12 mm [13]. A study reported by Sari Vähäaho, et al. in 2021 reported that as size increases, the 3-year occlusion rate decreases. A randomized controlled trial comparing mechanochemical and thermal ablation showed 3 year occlusion 100% for 6 mm, 87.5% for 7 mm, 75% for 8 mm [14]. If MOCA is performed on a large saphenous vein, follow-up for recurrence will be necessary.

Form sclerotherapy is recommended to be performed on blood vessels less than 6 mm [5]. This is because the recurrence rate was 62.6% for 6 mm or more. The Vanish-2 study also reported that the recurrence rate rose sharply when the thickness exceeded 7 mm [15].

Thrombophylaxis should also be considered in large diameters. Prophylaxis is could be helpful for Caprini scores of 7 or higher, although diameter is not essential component to calculate Caprini score. In a clinical study finding factors influencing the EHIT, mean Caprini score of the group with EHIT was 6.9±2.7, that was higher than non-EHIT group (5.0±2.1, p=0.004). Although only ultrasound-confirmed EHIT I to II were included in the study, the Caprini risk assessment score is likely to be able to predict the occurrence of EHIT (OR, 1.58; 95% CI, 1.24–2.0; p=0.0002) [16].

If a focal aneurysm is formed within 3 cm of the SFJ, the SVS guideline states that open surgical excision and high ligation should be performed. If it is more than 3 cm away, endovenous ablation can be done, but thrombophylaxis should be considered. Surgical excision was recommended for large varicose veins larger than 3 cm [4].

There is also a lack of clinical research reports on this, but when RFA was performed in 8 cases, the aneurysm size was reduced after surgery, and EHIT reported 1 case [17]. Although the number of cases is small, a paper reporting 4 cases of high ligation and 11 cases of endovenous ablation reported that since there was no EHIT, it was safe to perform only endovenous ablation without high ligation [18].

The following is information about vein diameter in compression stockings. The baseline venous pressure of deep veins is around 10–20 mmHg. It takes about 25 mmHg to press it into an oval shape, and 43 mmHg to completely collapse the vein [19].

The compression paradox is that, however, a higher pressure of 51 to 83 mmHg is required to collapse the saphenous vein in the subcutaneous tissue [20]. Therefore, when wearing compression stockings with class II, the deep veins are compressed, but paradoxically, the cutaneous venous system is not affected. Intramuscular pressure (IMP) is basically about 34 mmHg, but when wearing compression stockings, the pressure can be about 56 mmHg, which effectively compresses the venous system. In case of superficial veins, The skin veins only receive a pressure of 22 mmHg after wearing compressive stocking, and are not effectively affected by compression. The main effect of compression stockings is on deep vein system and have the effect of improving calf pump function. Therefore, inelastic compression is said to be more effective than graduated compression [20].

Vein diameter is important factor to diagnosis of varicose veins. We can differentiate the superficial veins with vein diameter to telangiectasia, reticular vein and varicose veins. Vein diameter is also important to decide treatment method for varicose veins. For the less large veins, many new modalities could be used safely and effectively. However, for large vein more than 10 mm, guidelines recommend to use endothermal ablation than non-thermal ablation. Some modification of endothermal method and thrombophylaxis may need to be considered to treat large vein. And further studies are needed to identify the effect of the treatment of very small varicose veins and non-thermal ablation for large veins.

The same topic is presented from the 46th congress of the Korean Society for Phlebology.

The authors declare no conflicts of interest.