Cockett syndrome (hereafter referred to as C syndrome) is a disorder of venous return to the lower extremities caused primarily by compression of the iliac veins and/or intraluminal adhesion structures. The recognition of this syndrome has a long history of almost a century.
Since 1980, when Kistner, on the basis of his experience, identified primary lower extremity deep vein valve insufficiency as a new disease, together with simple varicose veins of the large and small saphenous veins and the sequelae of deep vein thrombosis, constituted a new concept of chronic lower extremity venous disease, thus promoting the development of venous surgery. However, the C sign and its important role in the pathogenesis of the three diseases mentioned above have not been widely appreciated. Therefore, it is proposed to recognize this subject again, which will help to study the lower extremity venous diseases in depth.
I. The simple process of recognizing the C sign
As early as 1908, McMurrich saw the same abnormality in an autopsy. Although the association with deep vein thrombosis was mentioned, it was not recognized as a clinical syndrome. It was not until 1965 when Cockett and Thomas reported 2 patients with the first named iliac vein compression syndrome and discussed its mechanism and clinical presentation. With the increase of anatomical studies and clinical patient reports, it was found that in addition to the most compressed left common iliac vein, there are other types of compression and pelvic lesions that can also cause C-syndrome. Therefore, names such as May-Thurner syndrome, iliac vena cava compression syndrome, pelvic vein compression syndrome, and congenital and acquired iliac vein compression syndrome have emerged. However, the iliac vein compression syndrome is still mostly used. Many scholars believe that the collective name Cockett syndrome is appropriate.
In China, anatomical studies of left iliac vein compression and intraluminal adhesion structures, as well as literature reviews, phlebography diagnoses and clinical treatment experiences have been reported continuously since 1982. This information will contribute to the understanding and study of C syndrome.
II. Etiology
(A) Anatomical factors.
The right common iliac vein is almost straight, while the left common iliac vein runs transversely from the left side of the pelvis at a flat oblique angle and converges into the inferior vena cava at the plane of the fifth lumbar vertebra. The abdominal aorta descends from the left anterior parietal of the lumbar vertebrae, which corresponds to the plane of the lower edge of the fourth lumbar vertebrae dividing the left and right common iliac arteries, while the latter extends across the anterior side of the left common iliac vein to the lower right side of the pelvis. Therefore, the anterior compression of the left common iliac vein by the strongly pulsating right common iliac artery and the posterior compression by the anteriorly concave lumbar vertebrae constitute the basic reason why the left common iliac vein is vulnerable to compression injury. In addition, the left common iliac artery can also compress the inferior end of the inferior vena cava and the right common iliac vein, and the internal iliac artery can also compress the common and external iliac veins, but only rarely.
(b) Intraluminal adhesion structures of the iliac veins.
There are two explanations for the cause of venous adhesion structures.
1, congenital Some scholars believe that the adhesive structures are due to embryonic developmental abnormalities. paturet believes that the iliac veins originate from the caudal interiliac anastomotic branch of the left and right main veins, and the anastomotic branch mostly disappears after development is complete. McMurrich et al. did not find any inflammatory changes, while Erich et al. observed the presence of smooth muscle cells and other embryonic components. Fu et al. saw that 100% of full-term fetuses had a central type of adhesion structure, which gradually decreased after birth. This kind of adhesion structure should be the result of abnormal embryonic development.
2, Acquired intraluminal adhesion structures are found in the left iliac vein and have been increasing with age. As with extra-venous adherent cords and vein wall thickening, they are the result of postnatal compression manipulation by the right iliac artery. In 40 full-term fetuses, no such structures were found in any of the 40 cases except for the central stab, and in 127 cases by Erich et al. and 120 autopsies by Zhang Weilong et al. the rate of adherent structures was 33% and 27.5% in adults and 4.7% and 0.25% in children, and no smooth muscle tissue was seen in the structures by May et al. The above information provides a basis for the other adhesion structures outside the central spine to be mainly of acquired origin.
(iii) Pelvis
Other causes have been reported repeatedly as a result of pelvic occupational disease. Examples include lymphosarcoma, metastatic carcinoma, mucinous cystic tumor, lipodystrophy, and traumatic hematoma, abscess of the psoas major muscle due to sigmoid diverticulum, urinary retention of the bladder, and smooth muscle tumor of the iliac veins. There are some scarred cords formed after pelvic surgery and inflammation, which also have the possibility of triggering C-sign.
III. Pathophysiological characteristics and evolution
The hemodynamic changes of lower limb veins caused by luminal narrowing or obstruction triggered by internal and external factors of iliac veins are the basis of the pathophysiology and evolutionary process of C-sign.
(i) Lateral vessel formation
The presence of abundant collateral veins in the pelvis plays an important role in slowing down the hemodynamic changes of C sign. Taking the obstruction of the left common iliac vein as the side, it can pass through the internal iliac vein -> anterior sacral venous plexus and female organ venous plexus -> contralateral internal iliac vein; lumbar ascending vein -> middle, anterior and external sacral veins -> ventral thoracic and odd veins; pelvic veins -> vertebral venous system. The branch veins of the proximal deep and superficial veins of the lower extremities also play a role in the collateral circulation. The compensatory capacity of the collateral circulation is relatively high; for example, the sum of the diameters of the left iliolumbar, lumbar ascending and middle sacral veins can be enlarged by an average of 3 mm or less.C sign venous hemodynamic changes in the lower extremities do not appear or have only mild clinical manifestations when the collateral circulation is able to compensate or is not too loaded.
(ii) Evolutionary process
The degree of hemodynamic changes is determined by the degree of iliac vein obstruction and the resulting impairment of venous blood return. The evolutionary process is elevated pelvic and lower extremity venous pressure -> venous dilatation -> valve closure insufficiency -> superficial and spermatic varicose veins. In women, severe dilatation of the pelvic veins results in what is called “varicose veins of the parametrial tissue”.
Severe lesions in the internal and external iliac veins often result in significant stenosis or obstruction. This is the anatomical factor for the occurrence of iliofemoral vein thrombosis in C-sign.
IV. Clinical manifestations
C sign does not have specific clinical manifestations, and it is difficult to distinguish it from primary deep venous valve closure insufficiency and varicose veins of lower limbs only from physical signs and general examination. Together with the lack of recognition, it is conceivable that the misdiagnosis rate must be high. According to statistics, the rate of C sign with varicose veins of lower extremities is as high as 66.7 to 82.0%, and 16.4% and 35.7% of those who perform vein stripping. At this time there are also clinical manifestations common to other venous diseases of the lower extremities such as swelling, stasis dermatitis and ulcers. Without venography, it is difficult to make a clinical diagnosis of C sign.
In scholars, the clinical manifestations of C are classified as asymptomatic, edematous, iliofemoral vein thrombosis, and varicose veins of the spermatic cord. The asymptomatic type has no clinical significance. Iliofemoral vein thrombosis is closely related to C sign but is not an inevitable consequence of C sign, and there was no thrombosis in 14 cases of Bao Wen et al. Varicocele does not appear alone, but mostly coexists with other lateral branch veins of the body. It is feared that more often the C sign appears as the “face” of incomplete deep venous valve closure. The incidence is as high as 71.4%. Thus, the above-mentioned typology is not comprehensive.
The clinical manifestation of the C sign is determined by the degree of venous reflux impairment in the lower extremities. According to the severity of its hemodynamic changes, the clinical manifestations are divided into three stages.
Initial stage: only mild swelling of the affected limb, especially when standing and sitting for a long time. Ferii had three cases of swelling of the left lower extremity with prolonged standing, which was shown to be caused by compression of the left iliac vein. In 1993, Sloame et al. conducted a study of 215 elderly patients and found concave 3-mm deep edema of the lower extremities in 34.5% of 88 cases on the left side and 6.9% on the right side, and concluded that the edema of the left lower extremity in middle-aged and elderly patients was most likely due to compression of the lymph in the accompanying left common iliac vein by the right common iliac artery. Therefore, the possibility of this sign should be considered for lower limb edema without other causes.
Mid-term: A sustained increase in venous pressure with increased venous return obstruction can lead to deep venous valve closure insufficiency. Once it spreads to the calf and traffic branch venous valves, symptoms similar to those of primary deep venous valve insufficiency may develop.
Late stage: Clinical manifestations of severe deep venous valve closure insufficiency or iliofemoral vein thrombosis develop. The vast majority of nationally and internationally reported collapses are identified during the treatment of thrombosis. This is particularly important in patients with non-thrombotic venous obstruction phenomena and symptomatic venous obstruction. Because of the severe stenosis and limited obstructive lesions in the iliac veins and the better collateral veins, a similar but different clinical presentation from venous thrombosis is seen.
V. Specific diagnosis
Noninvasive venous testing methods such as Doppler ultrasound, resting and motile allergic volume tracing force, and dynamic venous manometry will be suggestive, but all lack specificity. MRI and spiral CT venography data have not been reported. Currently, only upper extremity paracentesis and femoral venous cannulation angiography are specific diagnostic methods and are known as the gold standard for the diagnosis of C sign. This was studied by Yu Jingbo et al. Their experience was that.
(a) In order to make satisfactory visualization of the iliac vein, the femoral vein is compressed with the fingers and the other hand is elevated 25 degrees on the affected limb, and the iliac vein is photographed quickly when the hand is released. If necessary, the femoral vein is cannulated into the external iliac vein to inject the contrast agent, which will be more clearly visualized. It is more satisfying to inject the contrast agent at high pressure for rapid film exchange or DSA imaging.
(B) The images show widening of the transverse diameter of the compressed vein, with a trumpet-like pattern at the top and bottom; limited filling stumps, fibrous cords and shadowing of adherent structures; and varying degrees of stenosis, such as impingement of the external iliac vein. Images such as venous occlusion or displacement by compression.
(iii) As previously described, there are varying degrees of pelvic collateral veins. Adhesive structures within the iliac veins are one of the main causes of the C sign, with varying morphology, for which there is a lack of imaging reports. Pressure measurement of the veins proximal and distal to the stenotic surface during femoral venous cannulation angiography is diagnostic if the pressure difference is 0.20 Kpa (2 cm H2O).
Based on the indifferent recognition of the C sign and the absence of specific clinical manifestations, as well as the fact that it is mostly detected in the three major venous conditions of the lower extremities, especially in the diagnosis and treatment of iliofemoral vein thrombosis, it makes treatment very difficult. At present, the common treatment methods can only be briefly described according to the characteristics of the lesion and the time of being diagnosed.
(a) Non-surgical treatment, like other common venous diseases of the lower extremities, is suitable for early patients with only mild lymphoedema or venous edema without surgical indications and for patients in the middle and late stages who do not undergo surgery. Commonly used are elastic medical stockings and appropriate limb motion disease in the early stages of the patient. The application of doxium, Aescurenforte, Bdazalpyroue or Alvenor has been shown to improve venous permeability and reduce limb edema. The appropriate symptomatic treatment can be used for patients with advanced disease.
(ii) Surgical treatment is the main treatment for C syndrome, which is a mechanical obstructive disease of veins, so the application of intra- and extra-venous surgery to improve its blood flow is the main treatment for C syndrome. The methods that have been applied are.
1.Venous stent (Stent) implantation it is suitable for patients with venous stenosis, simple operation and much good results. After determining the location of the stenosis, it is first dilated with a balloon (PTA) and then the selected stent is implanted. In patients with secondary thrombosis, the stent is implanted after thrombolysis or/and surgical thrombectomy.
2, iliac artery transposition In 1964 Calnon et al. transposed the iliac vein cut by the iliac artery and then reanastomosed it. Although the iliac vein is released from compression, the technique is complicated.
3, Iliac vein release and liner decompression surgery simply release the iliac vein without releasing the cause of its compression, it can not guarantee the surgical effect.
4.Venoplasty is the use of autologous vein patch grafting to enlarge the lumen of narrowed veins. This is suitable for patients who have narrowed lumen with hypertrophic wall and luminal adhesions after removal of the luminal structures.
5.Venous diversion is suitable for patients with complete obstruction of the iliac vein. One is the iliac-venous artificial vessel bypass; the other is the simpler subpubic tunnel femoral-femoral or saphenous vein and vein anastomosis (Palma-dale procedure). There are also arteriovenous fistulas that act simultaneously.
6.Other venous reconstruction
Surgical treatment of C sign is still rare, except for Taheri et al. who reported 18 cases at one time, Bao Wen et al. 10 cases and Zhao Jun et al. 28 cases, which are mostly individual cases or few case reports. For patients with venous stenosis, post-PTA stenting is the preferred method and is widely used with good results. The choice and results of other multiple procedures are to be summarized.
Sixth, deepen the understanding of C sign and its role in the occurrence of venous diseases in the lower extremities, it is found that the understanding of C sign and its main etiology has a history of nearly 100 years, characterized by the impact on the development, treatment and prognosis of the three major venous diseases of the lower extremities, which are more than 10 times that of arterial diseases, has not yet attracted due attention, thus preventing the progress of venous surgery. In this regard, based on domestic and foreign research data, the following issues are proposed to discuss with the interested parties.
(A) Overview of the development of C sign
Taheri et al. identified 18 cases (2%) of C-sign among 900 cases of lower extremity venous disease in middle-aged and elderly people, but it does not reflect the real situation of C-sign onset, because many patients were not diagnosed by venography. Anatomical studies can provide some reference data, such as the rate of the right common iliac artery riding across the left iliac vein is above 80%; the rate of compressed adhesions in the right common iliac vein is 20.5% (Table 1); the rate of intraluminal adhesion structures is 23.8% (excluding the central type, Table 2). Especially from the clinical point of view, Zhao Jun et al. found 76.1% of left common iliac vein stenosis and obstruction in the surgical treatment of lower extremity venous thrombosis.Dodd and Cockett concluded that most of the thrombotic peers in acute iliofemoral veins under 30 years of age are related to compression of iliac veins. In 1999, Dong Guoxiang et al. performed preoperative retrograde and left iliac venography in 73 consecutive cases of varicose veins in the lower extremities and found 35 cases (47.9%) of left iliac vein compression, which was called occult Cockett syndrome and played an etiological role in varicose veins in the lower extremities. 2000 In 2000, Hoshino et al. treated 73 cases of iliofemoral vein thrombosis with catheter thrombolysis, thrombus removal and systemic thrombolysis and found 14 cases (19.2%) with left iliac vein compression syndrome. If we speculate according to this, the incidence of C syndrome is quite high.
(II) The role of C sign in lower extremity venous disorders
Based on the hemodynamic protocols and evolution of C sign and the above clinical data, it can be concluded that a significant proportion of deep venous valve incompetence and thrombosis are likely to be the result of the development of C sign disease. Based on this view, satisfactory iliac venography should be available for patients with clinically diagnosed deep venous valve closure insufficiency. After surgical retrieval or thrombolysis of thrombosed patients, satisfactory iliac venography should also be available to determine the presence of iliac vein stenosis or obstruction. If there is, the stenosis or obstruction of the iliac vein must be addressed at the same time, otherwise it will definitely affect its treatment outcome and prognosis.
(iii) Early diagnosis problem
If the diagnosis of C sign can be made and effective surgical treatment can be performed before grade 3 or 4 valve incompetence, the valve with grade 1 or 2 incompetence will also recover its function due to the reduction of the canal diameter because there is no venous reflux obstruction and the venous pressure returns to normal. Cure is also possible for grade 3 and 4 insufficiency of closure. If the diagnosis and effective treatment can be made in the early clinical stage of C sign, the occurrence of thrombosis will be avoided or reduced. This shows the importance of early diagnosis of C sign. To make early diagnosis, the key issue is to raise the awareness of C sign. In the case of unexplained lymphatic or/and venous fluid in the left lower extremity, if general treatment is not effective, non-invasive venous examination and static and dynamic venous manometry should be performed, and if necessary, satisfactory iliac venography should be performed to make early diagnosis and effective treatment of C sign and to avoid or reduce the difficulty of late treatment.