The IJV catheterization is used in a variety of situations, including relatively short-term use, such as emergency or critical care, and long-term use, such as chemotherapy and hemodialysis [11
]. Recently, it has become possible to safely and easily insert a catheter into an IJV by using ultrasound guidance [4
]. However, in an emergency situation or in locations where there is no ultrasound machine, the procedure must proceed in a traditional method depending on external anatomical landmarks. IJV catheterization has no absolute contraindication, but it is cautioned against in certain situations, such as vascular damage, local infections, coagulopathies, and previous history of radiation therapy [13
Attention must be paid during IJV catheterization using only anatomical indices as IJVs can have different anatomies depending on the patient [14
]. In a study of hemato-oncology patients, 36% of them had unusual anatomical positions of their IJVs [15
]. A study of healthy individuals reported that there was a difference in IJV area according to age, sex, handedness, and cervical spine level [14
]. By contrast, our study found no difference in the right middle level IJV size with or without chemotherapy or by sex. The median right IJV (middle level) area was not different between those with chemotherapy and those without chemotherapy (190.87 (range 128.32–258.44) mm2
vs. 190.07 (range 137.74–256.38) mm2
= 0.499) and also between male and female patients (196.94 (range 142.80–273.48) mm2
vs. 184.62 (range 132.70–241.46) mm2
= 0.118). Rather, among the basic patient characteristics, there was a significant difference in the IJV area according to age and BMI. The older the patient, the lower the velocity of IJV blood flow and the lower the venous outflow volume [17
]. Moreover, as the emptying of the atrium decreases, the venous blood pressure increases, which, following induction beyond the capacity of the jugular vein valve, leads to an increase in venous resistance and regurgitation [17
]. These processes have been defined as venous dilatation. We could easily hypothesize that if a patient is clinically obese, then the thick fat layer could compress blood vessels [18
]. However, in this study, we found that the higher the BMI, the larger the size of the IJV. Even though the mechanisms are unknown, it is known that a higher BMI results in higher abdominal and thoracic pressures, which can limit venous flow return and cause venous dilatation [14
]. Although we were able to identify the factors that affected vessel size, we did not find clear cut-off values for practical application in the clinic.
The shape of the IJV is represented by a cylinder-like shape of a constant size in many medical anatomy textbooks [19
]. Recent studies have shown that the morphology of the IJV has a conical shape that increases in size to the subclavian vein from the cranial vault [5
]. Based on these results, it has been recommended to target the lower portion of the IJV when inserting a central line [5
]. However, according to this study, the IJV was observed to have a rhomboid shape, which was larger at the middle level and became smaller above and below. Therefore, we suggest that there is no benefit in accessing the lower portion of the IJV, as it may unnecessarily cause complications such as pneumothorax during central line placement. In addition, the size of the right IJV was larger than the left at all levels.
This study had several limitations. First, this study had a retrospective, single-center design and included relatively few patients. Care should be taken when interpreting and applying current results, as not all patients can provide accurate information given the retrospective nature of this study. Second, not all patients had the same physiological conditions. Depending on the patient’s condition, the size of the IJV may differ, but it was not possible to distinguish the patient’s condition at the time of taking the CT [22
]. Third, it was not possible to determine the overall vessel state by measuring only partial vessel sizes without measuring all successive position levels of the IJV. Fourth, all underlying diseases that could affect the IJV size, including chronic cerebrospinal venous insufficiency, could not be identified. Therefore, a detailed analysis of the morphology of IJV may be necessary through the prospective study.