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Surgical Management of Chronic Venous Obstruction
Reconstruction of the occluded iliofemoral vein or the inferior vena cava (IVC) may be required in patients with postthrombotic venous occlusion if they exhibit signs and symptoms of advanced chronic venous insufficiency (CVI). Reconstruction of large veins may also be needed in patients with traumatic or iatrogenic venous injuries or in those who undergo excision of primary or metastatic malignant tumors invading the IVC or the iliac veins. Nonthrombotic iliac vein lesions (NIVLs)—as seen in May-Thurner syndrome, which are caused by occlusion or stenosis of the left common iliac vein due to compression by the overriding right common iliac artery ( Fig. 51.1 )—can lead to acute deep venous thrombosis (DVT) more frequently than previously thought. Chronic NIVL can be symptomatic in up to one-third of the patients with CVI. The advent and development of intravascular ultrasound (DUS) and high-resolution imaging techniques have helped us to recognize that obstruction of the iliac veins occurs ubiquitously due to both postthrombotic and nonthrombotic lesions.
Venogram of May-Thurner syndrome with compression of the left common iliac vein by the overriding right common iliac artery (arrow) .
(Reproduced with permission of the Mayo Foundation.)
Endovascular treatment for iliocaval obstruction has progressed rapidly, and venous stenting is currently the primary choice for benign iliac, iliofemoral, or iliocaval venous occlusions in patients who fail conservative compression therapy (see Chapter 52 ). Further studies on the effectiveness of venous stenting are still needed, since comparative studies are few and the quality of evidence to support the use of deep venous stenting is still weak.
In the last 2 decades, results of open surgical reconstruction have also improved and symptomatic patients who are not candidates or who fail endovascular reconstruction can be treated with venous bypasses to relieve symptomatic venous outflow obstruction. A thorough preoperative evaluation to identify the underlying cause of CVI in these patients is essential.
Incidence and Etiology
In most series of patients with CVI, previous DVT is the most common cause of venous outflow obstruction. DVT is very prevalent; Heit and colleagues found that the incidence for DVT ranged from 45 to 117 per 100,000 person-years and that recurrent DVT ranged from 15 to 29 per 100,000 person-years. Postthrombotic syndrome (PTS) develops in 20% to 50% of patients with previous DVT, and about 5% to 10% will have advanced disease, including venous ulcers. There is evidence that PTS develops more frequently in patients who have proximal venous obstruction.
Venous outflow obstruction can also be the result of primary venous disease, most frequently of NIVL. May-Thurner syndrome is the most prevalent NIVL, although iliac vein compression has been described in other areas as well, including the right iliac vein. May and Thurner observed secondary changes, such as an intraluminal web or spur, in the proximal left common iliac vein in 22% of 430 autopsies. Kibbe and colleagues found that 24% of asymptomatic patients who underwent computed tomography for other reasons had greater than 50% compression of their left common iliac vein. Among 4026 patients with symptoms of chronic venous disease, iliac vein obstructive lesions were found in 938 limbs of 879 patients; 53% were nonthrombotic, 40% were postthrombotic, and 7% were a combination.
Other less common causes of venous outflow obstruction include retroperitoneal fibrosis; iatrogenic, blunt, or penetrating trauma; placement of an IVC filter; congenital venous anomalies such as deep venous agenesis or hypoplasia; and benign or malignant tumors.
The most frequent primary malignant tumor originating from large veins is venous leiomyosarcoma, and suprarenal involvement occurs in more than 40% of cases; three-fourths of these tumors involve retroperitoneal and abdominal veins. Secondary cancers or sarcomas that involve the IVC are more common than primary venous leiomyosarcoma. Renal cell carcinoma is the most common cancer involving the IVC and requires operative intervention, and the tumor thrombus in some patients may reach all the way into the right atrium, although invasion of the wall of the IVC is rare.
Congenital suprarenal caval occlusion can occur because of webs or caval coarctation that may also develop with associated hepatic vein occlusion (Budd-Chiari syndrome).
Pathophysiology
During the acute phase of DVT, the thrombus in the vein activates the inflammatory cascade, which in turn promotes partial lysis of the thrombus and leads to recanalization (see Chapter 49 ). However, these processes are also responsible for damage to the vein wall and to the venous valves, leading to chronic obstruction and valvular incompetence. If collateral venous circulation is inadequate, ambulatory venous hypertension develops because of a functional venous outflow obstruction and the incompetence of damaged valves. In the PTS, deep reflux and obstruction of multiple venous segments often coexist.
In a prospective study of 83 lower extremities with acute DVT in 78 patients, DUS was performed for follow-up study. Strandness and colleagues observed that at a median follow-up of 3 years (range 1 to 6 years), 41% of the limbs had features of the PTS. Additionally, limbs with PTS had over 3 times the odds of having combined reflux and obstruction than did limbs without the PTS (OR 3.5, 95% CI 1.4% to 8.6%). Factors that predispose patients to develop PTS include DVT involvement of the iliac vein, poor resolution of DVT, and recurrent DVT. The lesions can vary from stenosis to chronic total occlusion (CTO).
Nonthrombotic obstructive lesions in the ilieocaval vein segments are due to fibrotic or membranous stenosis that develops where the vein is crossed by arteries or fibrous ligaments. The lesions may be ontogenic or result from traumatic injury from repeated pulsations of the closely related artery. Because a majority of these patients are asymptomatic, Raju suggested the explanation of permissive pathologies—namely, that the venous obstructive lesions were permissive, remaining silent until additional insult such as trauma, cellulitis, or additional pathology such as venous reflux, DVT, or sedentary leg dependency precipitated symptoms.
Presentation
Unilateral limb swelling and pain during and after exercise that is relieved with rest and leg elevation (venous claudication) is the typical presentation of patients with chronic venous obstruction owing to previous DVT, PTS, or obstruction of the common iliac vein (May-Thurner syndrome). Patients with obstruction may also have symptoms similar to those associated with primary valvular incompetence, such as varicose veins, edema, skin changes, or venous ulcers; however, claudication and edema are usually more severe with venous obstruction, and relief with limb elevation is not as pronounced.
Depending on the extent of the collateral circulation, patients with outflow obstruction will have pain, swelling, and heaviness of the limb, and the most severe forms of venous obstruction can interfere with the viability of the limb. Obstruction alone can also result in skin changes and venous ulcerations. In the Mayo Clinic experience with 64 venous reconstructions performed in 60 patients with benign disease, the mean duration of symptoms was 6 years ( Table 51.1 ).
TABLE 51.1
Clinical Symptoms in 60 Patients Undergoing Venous Reconstructions for Benign Disease at the Mayo Clinic
From Garg N, Gloviczki P, Karimi KM, et al: Factors affecting outcome of open and hybrid reconstructions for nonmalignant obstruction of iliofemoral veins and inferior vena cava. J Vasc Surg 53(2):383–393, 2011.
| Symptom | n (%) |
|---|---|
| Venous edema | 56 (94) |
| Venous claudication | 54 (90) |
| Edema and claudication | 50 (84) |
| Healed ulceration | 8 (13) |
| Active venous ulcers | 12 (19) |
A collateral vein on the abdominal wall or across the pubic bone can be a sign of venous obstructive disease at the level of the groin or higher in patients with CVI. Kurstjens and colleagues compared 295 patients with a collateral vein on the abdominal wall or pubic bone, visible on physical examination, with a randomly selected control group of 365 patients without a collateral vein. This study found that abdominal wall collaterals have a 93% positive predictive value for deep venous obstruction, with a sensitivity of 68% to predict a high-degree iliac vein obstruction.
Clinical Evaluation
A detailed medical history may establish the diagnosis of primary, secondary, or congenital venous problems. The history should address previous DVT or thrombophlebitis, previous abdominal or pelvic interventions, trauma, tumor or symptoms of malignancy, personal or family history of thrombophilia, medication history (particularly oral contraceptive pills), smoking, obstetric history, and a family history of venous disorders (most patients with varicose veins relate their parents' or grandparents' disease).
An abdominal mass or lymphadenopathy can provide a clue to venous compression and outflow obstruction. Perineal, vulvar, or groin varicosities can be seen in iliac vein obstruction or internal iliac vein or gonadal vein incompetence causing pelvic congestion syndrome. Scrotal varicosities may be a sign of gonadal vein incompetence, left renal vein compression between the superior mesenteric artery and the aorta (Nutcracker syndrome), or occasionally IVC lesions or renal carcinoma.
Investigations
Plethysmography
Air or strain-gauge plethysmography is designed to evaluate the global leg hemodynamics by measuring reflux, obstruction, and calf muscle pump function (see Chapter 14 ). Venous plethysmography is rarely used today, but it can provide information on venous function in patients with CVI. Plethysmography quantifies venous reflux and obstruction and has been used to monitor venous functional changes and assess the physiologic outcome of surgical treatments. These studies can be helpful in patients with suspected outflow obstruction but normal duplex findings, or in those suspected of having venous disease because of calf muscle pump dysfunction but with no reflux or obstruction noted on duplex scanning.
A recent report, however, questions the value of plethysmography in patients with outflow obstruction. Although the positive predictive value was 95%, the sensitivity of air plethysmography (APG) was 35% and the negative predictive value was 30%. Thus APG did not prove useful in identifying chronic deep venous obstruction compared with DUS or magnetic resonance venography (MRV).
Duplex Scanning
Venous DUS should be performed in all patients with symptoms of CVI to help to define the location, cause, and severity of the underlying problem. The test is safe, noninvasive, cost-effective, and reliable and is recommended as the first diagnostic test for all patients with suspected CVD. It has a grade 1A level-of-evidence recommendation in the clinical practice guidelines of the Society for Vascular Surgery (SVS), the American Venous Forum (AVF), and of the European Society for Vascular Surgery (ESVS). DUS is also excellent for evaluation of both infrainguinal venous obstruction and valvular incompetence. In the PTS, DUS identifies residual obstruction, persistent occlusion, and valvular incompetence in the affected segments, with greater accuracy in the infrainguinal areas.
The four components that are essential in a complete duplex scanning examination for CVD are visibility, compressibility, venous flow, and augmentation. The typical appearance of a postthrombotic vein during duplex scanning is that of a thickened, hardly compressible vessel with damaged, incompetent valves and variable degrees of venous flow owing to partial recanalization. Asymmetry in flow velocity, lack of respiratory variations in venous flow, and waveform patterns at rest and during flow augmentation in the common femoral veins indicate proximal obstruction. Obesity and bowel gas may prevent good visualization of the iliac veins, vena cava, and common hepatic veins with ultrasound.
Metzger and colleagues studied the sonographic criteria for the diagnosis of iliac venous outflow obstruction by assessing the correlation of DUS with intravascular ultrasound (IVUS) in patients with advanced CVI. DUS had high agreement with IVUS for the detection of obstructions 50% or greater. The velocity ratio equal to or greater than 2.5 was the best criterion for the detection of significant venous outflow obstructions in iliac veins. Monophasic flow of the common femoral vein at rest and continuous flow during the Valsalva maneuver are highly suggestive of iliac vein obstruction.
Computed Tomography and Magnetic Resonance Venography
Early venous disease (C 1-2 ) rarely requires advanced imaging studies in addition to DUS. Computed tomography and magnetic resonance venography have progressed in the last decade and provide excellent three-dimensional imaging of the venous system. Both modalities are suitable for identifying pelvic or iliac venous obstruction in patients with lower limb varicosities when proximal obstruction or iliac vein compression (May-Thurner syndrome) is suspected. Venous phase examination will help to identify any obstructing mass or tumor and provides sufficient information in most patients about venous anatomy, obstruction, or stenosis. The sensitivity of imaging techniques can be increased if diameter measurements of the iliac vein segments are included for comparison with anatomic norms for assessment.
Contrast Venography and Hemodynamic Studies
Diagnostic ascending or descending (or both) contrast venography for CVI is performed only selectively in patients with postthrombotic syndrome and suspected deep venous obstruction. Ascending venography is performed with the patient in a standing position to evaluate patency of the superficial and/or deep venous system. Ascending venography is useful as a map of the deep veins of the limb; it defines the sites of obstruction and images the collateral venous circulation and the patterns of preferential flow. Descending venography is used to study associated venous valve incompetence with Valsalva maneuver and classifies the severity of reflux (grade 1 to 4 : 1 = to upper thigh; 2 = to distal thigh; 3 = popliteal reflux; 4 = reflux to tibials and perforators). This test has been much less frequently used in recent years. The relatively low sensitivity of single-plane transfemoral venography can be increased by biplane imaging and by measurement of femoral venous pressure measurements during venography.
Contrast venography is routinely used in CVD before performing endovenous procedures, such as angioplasty or venous stenting, and it also helps in planning open venous reconstructions. A pressure gradient across iliofemoral obstruction of 3 mm Hg at rest in the supine patient or 10 mm Hg after exercise confirms functional venous obstruction. Exercise consists of 10 dorsiflexions of the ankles or 20 isometric contractions of the calf muscle. Arm or foot venous pressure tests and ambulatory venous pressure measurements in a dorsal foot vein are additional tests that can be performed. Detailed descriptions and techniques for these tests are provided in the consensus statement.
Intravascular Ultrasound
Studies have shown that IVUS is useful tool to detect and assess iliofemoral venous occlusive lesions in patients with suspected or confirmed iliac vein obstruction. IVUS can be used in veins with stenosis without occlusion to assess the venous wall morphology and mural thickness; it can also identify trabeculations and recanalization, frozen valves, and external compression. Some of these lesions, as emphasized by Neglen and Raju, are not seen with conventional contrast venography. IVUS provides measurements in assessing the degree of stenosis and is useful to measure surface area and assist in the selection of stent size. IVUS has also been used as a comparative method to examine the sensitivity of DUS in detecting venous obstructive lesions. In addition, IVUS confirms the position of the stent in the venous segment and the resolution of the stenosis.
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