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Dept of Medical Imaging, University Hospital Sart Tilman, Liège, Belgium
CORRESPONDENCE: B. Ghaye, Dept of Medical Imaging, University Hospital Sart Tilman B 35, B-4000 Liège, Belgium. Fax: 32 43667772
Keywords: arteries, interventional radiology, stents, therapeutic blockade, thorax, transthoracic biopsy
Received: October 10, 2000
Accepted December 27, 2000
Abstract
Interventional Radiology is a technique based medical specialty, using all available imaging modalities (fluoroscopy, ultrasound, computed tomography, magnetic resonance, angiography) for guidance of interventional techniques for diagnostic or therapeutic purposes.
Actual, percutaneous transthoracic needle biopsy includes core needle biopsy besides fine needle aspiration. Any pleural, pulmonary or mediastinal fluid or gas collection is amenable to percutaneous pulmonary catheter drainage.
Treatment of haemoptysis of the bronchial artery or pulmonary artery origin, transcatheter embolization of pulmonary arteriovenous malformations and pseudoaneurysms, angioplasty and stenting of the superior vena caval system and percutaneous foreign body retrieval are well established routine procedures, precluding unnecessary surgery. These techniques are safe and effective in experienced hands.
Computed tomography is helpful in pre- and postoperative imaging of patients being considered for endobronchial stenting. Many procedures can be performed on an outpatient basis, thus increasing the cost-effectiveness of radiologically guided interventions in the thorax.
When adequate vascular catheters, wires and other devices, such as snare loops became available, percutaneous foreign body retrieval from the heart or pulmonary arteries became applicable 12. The introduction of expandable metal vascular stents further broadened the spectrum of closed minimally invasive techniques in the chest, allowing for minimally invasive treatment of superior vena cava (SVC) obstruction with an immediate clinical result 13. The most prominent interventional radiological techniques in the chest mentioned earlier will be discussed in this paper.
Percutaneous nonvascular interventions
The various percutaneous nonvascular applications that are in clinical use in the authors’ department are listed in table 1
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Imaging techniques used for the guidance of interventional procedures include fluoroscopy and cross-section imaging or a combination of both 14. A comparison of the different imaging modalities for percutaneous biopsy or drainage of thoracic lesions is given in table 2.
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Computed tomography
CT offers exquisite anatomical display of all the thoracic structures and allows percutaneous access to all spaces with equal ease 14, 19–23, 28–33. Intravenous contrast medium injection is mandatory for identification of necrosis, fluid content, normal vascular structures and false aneurysm located in an abscess wall, and also contributes to a precise delineation of a lesion with regard to the anatomical environment. CT is particularly useful for guiding puncture of a mediastinal lesion and an intrapulmonary lesion that is difficult to localize with fluoroscopy alone 29, 34. CT allows for determination of an optimal cutaneous entry point in such a way as to avoid transgression of a pleural fissure or puncture of large vessels, bronchi and the oesophagus. The spiral scanning capability was not proved superior to sequential scanning 35. Real time CT (fluoro-CT or continuous CT) is now widely available and combines the advantages of cross-section imaging and real time control of the procedure 36, 37.
Ultrasonography
Apart from it being the primary imaging guidance for biopsies of the chest wall or pleural lesions as well as lesions located in the anterior mediastinum 38, 39, ultrasonography (US) is particularly indicated to guide bedside percutaneous aspiration and catheter drainage of a pleural or pericardial fluid collection, even of only small amounts 19–22, 28, 40–43. A subpleural pulmonary effusion and some pulmonary lesions with a parietal contact can also be punctured with US control 44–47. The percutaneous approach is performed in the patient's position that optimally displays access to the lesion.
Magnetic resonance
Guidance of percutaneous interventions is a promising application of magnetic resonance (MR) 48, 49. Little clinical experience is gained so far in thoracic interventions.
Transthoracic needle biopsy
In general, percutaneous tissue sampling of a pulmonary, pleural, or mediastinal lesion is performed when histological diagnosis will modify staging of the disease, influence therapeutic strategy, and when the diagnosis cannot be established by bronchoscopic techniques. TNB can be used as a less invasive alternative to mediastinoscopy in some mediastinal lesions as well as medical thoracoscopy in pleural pathologies.
Indications
Main indications for TNB are 14: indeterminate thoracic nodule or mass; pulmonary nodule suggestive of malignancy, surgery being postponed after chemotherapy and/or radiotherapy or replaced by these treatments; nodule in a patient with a clinical history of extrapulmonary primary malignancy, the patient being in clinical remission or presenting multiple primary malignancies; residual nodule following radiotherapy or chemotherapy; tissue sampling for therapeutic sensitivity tests, measurements of tumour markers, hormonal dependence, deoxyribonucleic acid (DNA) analysis, etc; chronic diffuse pulmonary infiltrate and evaluation of suspected focal infectious disease in normal or immunocompromised patients. The need for preoperative diagnosis of a solitary pulmonary nodule varies between institutions, and depends on the pretest probability of diagnosing a lesion that would obviate an unnecessary surgical thoracoscopy or thoracotomy 15. The technique is faster, better tolerated and less expensive than surgery. Percutaneous puncture could also be indicated in localization of a lung nodule with a wire or a hook, or pleural tagging prior to video-assisted thoracic surgery (VATS) 50–53. All mediastinal compartments are accessible to TNB, which is a useful alternative or add-on to mediastinoscopy or mediastinotomy for cytologic or histologic diagnosis of a hilar or mediastinal mass and for staging of lung cancer.
Contra-indications
There is virtually no absolute contra-indication to TNB 14, 54. A vascular structure, hydatid cyst, meningocele or mediastinal pheochromocytoma is usually correctly diagnosed with imaging and/or laboratory tests. Coagulation disturbances should be recognized and corrected before sampling. Puncture of only one functional lung, chronic respiratory insufficiency, pulmonary arterial hypertension, cardiac insufficiency and severe emphysema are relative contra-indications that may increase the complication rate of TNB or render any complication more significant. Dyspnoea or intractable cough or any other inability of the patient to cooperate may be overcome by the use of real time guidance techniques, such as fluoroscopy, US, or fluoro-CT and, if possible, appropriate medication.
Results
TNB has an accuracy varying 80–95% in the confirmation of pulmonary malignancy or malignant mediastinal adenopathy 14, 29, 34, 55–63. The negative predictive value of pulmonary biopsy is 84–96% and false positive results are noted in 2–4% 3, 64. The diagnostic accuracy for small nodules with a diameter of <2 cm is similar to that of larger lesions in experienced hands 65, 66 (fig. 1). A large number of cutting or aspiration needles, including automatic guns, with a needle calibre of <1 mm and a variable tip design are currently used. Almost all needles allow cytological and histological sampling and give similar rates of results and complications concerning diagnosis of malignant or infectious disease. A specific benign diagnosis is more frequently established using a core biopsy needle than on aspiration of clusters of cells (44–100% versus 12–47%) 67–74. Cutting needle biopsy also provides sufficient diagnostic material in patients with mediastinal lymphoma to guide therapy in 81–95% of patients, as well as in diffuse pleural thickening 15, 67, 75–79 (fig. 2). If the sampled material is inadequate or insufficient, but there is a cytologic or clinical suspicion of malignancy, biopsy should be repeated.
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). Haemorrhage, with or without haemoptysis, is encountered in <10% of TNB, most of which are self-limited 14, 55, 64. Other complications, such as malignant seeding along the needle tract or air embolism, have become exceptional observations since the introduction of fine needle biopsy 82, 83. TNB related death rate is estimated at 0.02% 55.
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. A recent study on the influence of TNB on treatment showed that management was altered in 51% of patients and unaltered, i.e. confirmed the diagnosis of a resectable malignancy or provided nondiagnostic results in 49%. Surgery was avoided in 83% of biopsies that altered patient treatment 84. When the pretest likelihood of malignancy of a resectable lesion is high, proceeding directly to thoracotomy is appropriate since preoperative TNB is unlikely to alter patient management 15. Otherwise, TNB and fiberoptic bronchoscopy (FOB) must be considered complementary and TNB performed only after a negative FOB. In indeterminate pulmonary nodules, VATS may be the method of choice, providing simultaneous diagnosis and treatment and reducing total cost (table 3).
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Image guided percutaneous aspiration or drainage of fluid (or air) collection is considered a valid alternative to surgery. Increased safety and effectiveness compared to blind techniques have been largely demonstrated. Any collection located in the pleural space, pericardium, lung or mediastinum can be aspirated or drained percutaneously with catheter placement under imaging guidance.
Pleural collections
Pleural effusions, including empyema, haemothorax, chylothorax and pneumothorax can be considered for percutaneous closed catheter drainage.
Empyema
Indications for catheter drainage depend on the evolutionary stage of the pleural effusion, according to the classification of Light 85–87. The early stage (exsudative phase) corresponds to the secretion of a protein rich fluid by the pleura. This is a mandatory transitional phase for empyemas and does not require drainage. The second stage (fibrinopurulent phase) is characterized by a viscous and opaque fluid with increased cellularity. Deposition of fibrin layers on the pleural surface promotes the formation of pleural pockets and progressive lung entrapment. Medical treatment without effective fluid drainage might fail. The third stage (organizing phase) is characterized by fibroblastic infiltration of the pleura, limiting the expansion of the underlying lung due to pleural peels. Early drainage of a complicated effusion is necessary to prevent progression to the organized phase, which requires surgical decortication. In surgical treatment, blind placement of a thoracostomy tube (30F–34F) is followed by open surgical drainage if unsuccessful, although some surgeons recommend early open drainage, and pleural decortication, as the initial therapeutic approach 85, 88.
Imaging guided percutaneous drainage avoids the potential failures associated with blind chest tube placement, which can occur in about 50% of patients due to inadequate positioning of the tube or to undrained satellite pleural pockets 86, 87. The size of the percutaneous catheters that are in regular use varies from 7F–30F and is chosen according to the viscosity of the fluid to be drained. CT discloses all satellite noncommunicating pleural pockets, that are drained with multiple catheters. Pleural fluid, which is encapsulated in a fissure can also be adequately drained with CT control, most often without transgression of normal lung by the catheter. Technical success is achieved in almost all cases. Clinical success is achieved in 70–89% of the patients treated in a first intent, depending on the stage of empyema 14, 17, 20–22, 25, 27, 28, 31, 32, 41, 42. A similar success rate of 80% is obtained in patients treated in a second intent following failed surgical chest tube drainage 14, 17, 21–23, 27, 28. Failure of percutaneous drainage varies 11–30%, and usually occurs in chronic empyema (stage III), when extensive pleural peels have formed, which may prevent catheter insertion, or the cavity to collapse and obliterate. CT may have its difficulties to accurately differentiate between the fibrinopurulent and organizing phase of empyema 89. Medium sized catheters are better tolerated by the patient than large thoracostomy tubes, but their lumen is more prone to obstruction by fibrin products. Intrapleural injection of fibrinolytic agents was recently proven to be efficient in preventing fibrin deposit and formation of secondary loculation of the empyema, with a clinical success rate of 62–100% 14, 23, 26, 90–104. Local instillation of fibrinolytics also reduces the number of drainage catheters, that are necessary to drain all loculations, duration of drainage and hospitalization and prevents fibrosis of the pleural surface (fig. 4). Table 4 summarizes the basic principles and recommendations for successful treatment of complicated pleural empyema. Overall, the added cost of imaging guidance is largely compensated for by the savings from an increase in clinical success.
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Haemothorax
Post-traumatic haemothorax is usually drained by large-bore surgical chest tubes. In selected cases with persistent intercostal or phrenic artery bleeding, angiography and transcatheter embolization is indicated before drainage. Long-lasting multiloculated haemothorax is an indication for image-guided catheter drainage. Fibrinolytic agents can be safely injected in a pleural haematoma at 1 week following trauma 97, 98 (fig. 4
). Uncontrolled intrapleural bleeding is an absolute contra-indication of intrapleural fibrinolysis.
Pneumothorax
Postbiopsy or spontaneous pneumothorax can be drained percutaneously with a small calibre catheter (fig. 5). Success rate of drainage of iatrogenic pneumothorax is 75–97%, the vast majority resolving within 24–72 h 18, 19, 25, 86, 107, 108. Catheters can be connected to a one-way Heimlich valve. Recurrent pneumothorax can be treated with chemical pleurodesis if surgical therapy is not an option.
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). Resolution of the abscess is obtained in 73–100% following 10–15 days of drainage 7, 30, 31, 33, 40, 109–113. Pulmonary abscesses may have a thick wall and complete collapse of the cavity may take 4–5 weeks. Decompression should be performed slowly to avoid rupture of a vessel or a Rasmussen pseudoaneurysm incorporated in the abscess wall. Surgery remains necessary when extensive necrotizing pneumonia or life-threatening haemorrhage has occurred 14.
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Pneumatocele and bulla
Percutaneous drainage of infected or tension pulmonary pneumatocele has been described 14, 122. A percutaneous diagnostic aspiration with an 18-Gauge needle can precede catheter insertion in doubtful cases, as bullae may frequently contain an air fluid level, without infection.
Mediastinal collections
Abscess
Mediastinal abscesses are challenging to treat by a closed percutaneous approach, as overall prognosis of the patient is usually poor. Mediastinal collections can be drained under CT guidance using a parasternal catheter approach for collections located in the anterior mediastinum (fig. 7) and a posterior paraspinal approach for safe access to the posterior and middle mediastinal compartments 14, 27.
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Pericardial effusion
Most pericardial effusions are drained under US control using a subcostal or a subxyphoid approach 126. When US fails, fluid can be drained under CT guidance, by an atypical left anterolateral approach 127 (fig. 8).
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Others
Ectopic pancreatic pseudocysts, pleuropericardial, parathyroid or bronchogenic cysts, necrotic tumours, lymphoceles and haematomas can be drained or aspirated percutaneously using imaging guidance 14.
Vascular interventions
Vascular interventions that are in clinical use are listed in table 5.
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Bronchial artery embolization
Indications
Haemoptysis can be classified as massive (>300 mL in 24–48 h), moderate (
3 episodes of >100 mL within a week) and chronic (quantitatively small episodes of haemoptysis repeated over the course of weeks or months). Massive haemoptysis carries a high mortality rate in patients treated conservatively, and many patients are unfit for lung resection. When surgery is performed in an acute situation, morbidity is high and a mortality rate of 35% has been reported 129–133. Most frequent causes of bleeding include tuberculosis, chronic infection, bronchiectasis, aspergilloma, pneumoconiosis, bronchogenic carcinoma, pulmonary metastasis and pulmonary infarction 132, 134–136. Chest radiography and bronchoscopy should be obtained immediately to localize the site of bleeding. CT may be considered in noncritical patients to search for the underlying cause or determine the exact bleeding site whenever chest radiographs are inconclusive. In cases of massive haemoptysis requiring an urgent embolization, angiography is recommended as the initial intervention. Following embolization, surgery can be carried out in a second intent for localized disease 133. In moderate or chronic haemoptysis, bronchial embolization is the only treatment, when unresponsive to medical treatment in the following situation: recurrent haemoptysis following surgery, postradiation lung, unresectable carcinoma, bilateral pulmonary disease, inadequate lung function to tolerate resection, failure to localize a bleeding source roentgenographically and/or bronchoscopically, and large transpleural connections between bronchial and nonbronchial systemic arterial supply.
Technique
A thoracic aortogram is always obtained to map all bronchial arteries and systemic nonbronchial feeders of the bleeding site. Selective opacification of all bronchial arteries is then performed beginning with the vessels directed to the suspected bleeding area. Arteries with an increased calibre, and a tortuous course and parenchymal hypervascularity are found (fig. 9). Contrast extravasation in the lung parenchyma or in the bronchial lumen is not required to decide on embolization. Vaso-occlusion is best performed through a microcatheter that is inserted coaxially through a diagnostic catheter, the tip of which is placed in the proximal portion of the vessel or at its ostium. Microcatheters, which can be placed selectively distal to the origin of a spinal artery are not occlusive and allow for optimal catheter stability and safety during embolization avoiding reflux of embolization material 136–138. Polyvinyl alcohol particles, gelfoam and dextran microspheres are among the agents that are in frequent clinical use. Additional bronchial and nonbronchial collaterals (internal and external thoracic arteries, periscapular arteries, cervical arteries, intercostal arteries and inferior phrenic artery) are catheterized and may be treated, when their contribution to the hypervascular area is shown on angiography 132, 139, 140 (fig. 10). Nonbronchial systemic collaterals may resume the distal bronchial circulation after a previous bronchial embolization and be responsible for bleeding recurrence 141.
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Complications
Complications are encountered in 1% ofthe patients. A postembolization syndrome may beobserved (pleuritic pain, fever, dysphagia, leukocytosis); it will last for 5–7 days and responds to symptomatic treatment 143. Bronchial wall or oesophageal wall necrosis, inadvertent facial or abdominal visceral embolization, myocardial infarction and spinal cord infarction are rare complications that can be avoided by proper technique.
Pulmonary artery embolization
Arteriovenous malformation
Indications
Pulmonary arteriovenous malformations (PAVMs) are arteriovenous shunts which represent a potential source of paradoxical emboli through a right to left shunt, without altering pulmonary artery pressure or cardiac output. Other potential complications include systemic oxygen desaturation resulting in polycythaemia, and haemoptysis or haemothorax caused by rupture of the aneurysmal sac. Most PAVMs are congenital and multiple, being part of the hereditary haemorrhagic telangiectasia (Rendu-Weber-Osler) syndrome, while a minority are acquired, mainly secondary to vascular damage 136, 144–147. They can be classified as simple (one segmental feeding artery: one draining vein) or complex (several segmental feeding arteries: one or several draining veins) 148, 149. Before 1980, surgical lobectomy or pulmonary wedge resection was the only valid therapy. Selective embolization is at present considered the treatment of choice for PAVMs which show a feeding artery superior to 3 mm in diameter. In fact, large shunts are associated with an increased incidence of paradoxical emboli potentially causing severe neurological complications 146–153. Multiple microscopic shunts are usually present in addition to the visible fistulae and small AVMs may increase in size during lifetime. Endoluminal embolization offers the advantage of a maximal preservation of normal lung parenchyma around the malformation, particularly in patients with multiple and bilateral PAVMs.
Technique
Pre-embolization thin section helical CT with 3D reconstruction of the PAVM is an important step in identifying all small feeding arteries, which may be responsible, when not recognized, of persistent shunting following embolization of the main feeder only 149. Selective transcatheter embolization of all feeding arteries is performed with steel coils with attached cotton strands (fig. 11). All catheter and guidewire exchanges and coil introduction into the catheter are performed "under water" to avoid air embolism to the brain. Compact placement of endoluminal coils and choice of large "tornado" shaped coils or use of a controlled coil detachment technique are important keypoints for successful treatment to avoid transfistulous coil migration. The site of groin access should be alternated in multiple interventions to avoid femoral vein thrombosis.
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Complications
Potential complications are encountered in <10% of the patients and include pulmonary infarction distal to the occlusion, pleurisy, sepsis and retrograde pulmonary embolism in patients with polycythaemia.
Pseudoaneurysm
Destructive processes of any origin, including trauma (particularly iatrogenic, i.e. Swan-Ganz catheter), infection, tumour, and inflammatory disease, can erode the wall of a pulmonary or bronchial vessel, and lead to the formation of a pseudoaneurysm 154. Prompt therapy is required, as false aneurysms are at risk of enlargement and rupture, which can lead to lethal haemoptysis in >50% of the patients 155. Multiple therapeutic procedures have been used to control pulmonary artery bleeding. Palliative measures include Swan-Ganz balloon tamponade of the affected vessel and endobronchial tube placement with positive end-expiratory pressure. Surgical management generally comprises resection of the involved lobe, or in selected cases, aneurysmectomy 155. Endoluminal catheter embolization of the parent artery with steel coils has emerged as an alternative noninvasive technique, particularly in emergency cases 154, 156. Intrasaccular embolization with steel coils has the advantage of preserving the distal pulmonary artery and sparing of pulmonary function distal to the pseudoaneurysm 154 (fig. 12).
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Rationale
The potential of the venous system to collateralize and the usually nonacutely lethal nature of SVC obstruction are the main reasons why medical management and radiotherapy are preferred to other invasive therapeutic procedures for correction. Percutaneous transluminal angioplasty (PTA) is rarely successful in large vein obstruction, due to elastic recoil of the venous wall and/or persistent perivascular compression. The rationale for using expandable metal stents in benign and malignant SVC obstruction is the immediate and permanent achievement of venous patency.
Indications
Potential indications for percutaneous stenting of the SVC and innominate veins are mainly primary or secondary malignant tumours with mediastinal location, such as bronchogenic carcinoma, lymphoma, or metastatic adenopathy and benign stenoses related to central venous lines, haemodialysis shunts, and rarely postoperative anastomotic stenoses, or fibrosing mediastinitis 13, 157–161.
The advantage of endoluminal desobstruction over radiation therapy or chemotherapy is the immediate correction of disabling symptoms and the still possible application in patients who have already received the maximum radiation dose. Patients with imminent SVC obstruction should be treated before they become fully symptomatic, when encasement of the innominate vein, SVC bifurcation is suspected, as a Y-shaped stricture is technically more difficult to treat than a straight vein segment. Multiple and bilateral stents might be required to treat the bifurcation and regional thrombolysis, preceding stent placement might be necessary to clear the lumen from thrombosis before stenting. Patients in whom nephrotoxic chemotherapy or other nephrotoxic drugs are given and patients in whom extensive tumourlysis with hyperuricaemia, hypercalcaemiaand emesis-related dehydration is expected may also benefit from SVC desobstruction to increase tolerance of high volume hydration, even if clinical symptoms of venous stasis are not prominent.
Relative contra-indications include preterminal patients with malignant disease, extensive chronic venous thrombosis, endoluminal tumour growth, and upper limb paralysis. Occlusion of the ostium of the azygos vein is not a contraindication. Mechanical thrombectomy using rotational catheters or other devices should not be used in the SVC system, because of the risk of pulmonary embolism by a jugular vein thrombosis, that may become mobilized after successful clearance of the downstream veins. Patients with simultaneous tracheobronchial and mediastinal vein obstruction should undergo stenting of the airways first.
Technique
Although SVC stenting is a straight forward procedure in simple cases, it can become extremely complex in cases with extensive obstruction. Phlebographic demonstration by a bilateral arm injection of contrast medium is mandatory before treatment, to locate the obstruction, appreciate its haemodynamic significance, extent of collateral venous drainage and any congenital variants and to allow planning of the stenting procedure (fig. 13). In patients with severe oedema of the upper limbs, puncture of the axillary vein may be targeted by a peripheral hand vein injection of carbon dioxide. In case of acute or subacute venous thrombosis, local catheter directed thrombolysis may be indicated, using an infusion of 70,000–100,000 IU of urokinase per hour or another plasminogen activator. Chronic occlusion is recanalized with catheter-guidewire techniques by a unilateral or bilateral axillary vein or a femoral vein approach, or a combination of both. Self-expandable and flexible metal stents are placed, when necessary, multiple and bilateral and in an overlapping position. Stent placement in the subclavian vein should be prohibited because of the risk of subclavian vein thrombosis or stent fragmentation by external clavicular compression. Stents in large veins should be oversized by 25–50% compared to the diameter of a fully dilated normal vein. PTA is not indicated prior to stenting in malignant disease, but should be performed after stenting to establish optimal venous return immediately. In stenosis of benign origin, PTA is indicated prior to stenting to probe the degree of stenosis and for precise localization of maximum of resistance within the stenosed venous segment. Perprocedure heparinization is advised in all cases 162, 163.
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Complications
Complications of venous desobstruction are few. Local thrombolysis may lead to haemorrhagic complications. Stent related complications include misplacement or migration, uncomplete stent opening, formation of de novo thrombosis, and pulmonary embolism. Vein perforation, significant infection, phrenic nerve deficit by stent compression or puncture site complications are rare.
Percutaneous vascular foreign body retrieval
Indications
Since its introduction, percutaneous catheter mediated vascular foreign body retrieval has emerged as the treatment of choice, avoiding thoracotomy and open heart surgery 12. The growing clinical application of intravascular devices in interventional radiological practice has increased the risk for central venous embolization of many types of foreign materials besides the classical lost central venous lines, Swan-Ganz catheters, ventriculo-atrial shunts, port-a-caths, cardiac stimulator lines and pacemaker electrodes. All intravascular embolized foreign bodies should be retrieved, as they are potentially associated with serious complications according to their type and location. A 21–71% long-term serious morbidity and a 25% death rate was reported 169–173. Expected complications from a foreign body that is partially or entirely blocked in the right heart are ventricular arrythmia, myocardial infarction, myocarditis, recurrent pericardial effusion, tamponade and sepsis. Foreign bodies blocked in the pulmonary circulation may be responsible for thromboembolism and sepsis. Relative contra-indications of catheter retrieval are free floating thrombus attached to the foreign body and chronic incorporation of the foreign body in a thrombus or vessel wall.
Technique
Vascular foreign bodies are located with fluoroscopy and, when necessary, phlebographic demonstration. Extraction devices are relatively inexpensive and based on the loop-snare technique, helical basket entrapment or the grasping forceps technique or a combination of the above and other catheter-guide wire dislodgement techniques (fig. 14). The procedure is carried out under fluoroscopic control and with local anaesthesia. Large and uncompressible foreign bodies may require a femoral venotomy for extraction. Large stents retrieved from a pulmonary artery or from the heart can be abandoned in an iliac vein.
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Endoluminal tracheobronchial stenting
Indications
Tracheobronchial airway obstruction is a relatively common condition. Various therapeutic options are available and depend on the cause (benign versus malignant), location (central versus peripheral) and origin (intrinsic versus extrinsic) of the stenosis. Patient's condition and the prognosis of disease are also considered. Whenever possible, in malignant obstruction or in benign stenosis, surgery is the first choice 174. With progress in technique, local treatment by bronchoscopy (laser, cryotherapy, electrocautery, photodynamic therapy, brachytherapy) has been used with increasing frequency 175–179. Balloon dilatation leads to a rapid improvement of the respiratory function after treatment of malignant and benign bronchial stenosis, but relief of symptoms is often short-lasting 180, 181. Therefore, indication of stents placement in the tracheobronchial tree has increased in frequency and can be placed under radiological or bronchoscopic control, or a combination of both modalities 181, 182. Compared to surgery, stent insertion is a simple palliative method, resulting in immediate improvement in acute respiratory distress from airway obstruction 181. In nonsurgical patients with malignant disease, indications of tracheobronchial stenting are: extrinsic compression or submucosal disease; tracheo-oesophageal fistula; and obstructive endobronchial tumour unresponsive to endobronchial treatment by debulging or resection, respectively 181–190. In benign stenosis, surgery may not be indicated in patients with a short life expectancy or extensive airway stenoses. Stent insertion for benign stenosis has been reported in the following conditions: iatrogenic (postintubation or postanastomotic stricture); tracheobronchial malacia in children; extrinsic compression from vascular structures or fibrosing mediastinitis; tracheobronchial infection (tuberculosis); and systemic disease (Wegener's granulomatosis, relapsing polychondritis and amyloidosis) 181, 182, 184, 190–196.
Technique
Precise measurements of the diameter of the tracheal and bronchial lumen and location of the stenosis compared to anatomical landmarks are performed with spiral CT before the procedure. Stents are inserted under sedation or anaesthesia, following previous dilatation or laser ablation of the stenosis under fluoroscopic and endoscopic control. Two types of endobronchial stents are currently available in the tracheobronchial tree: silicone stents (Dumon, Dynamic, Reynders, and others) 181–183, 186, 188, 190 and metallic stents, the latter including either balloon expandable stents (Palmaz and Strecker) or selfexpanding stents (Gianturco, Wallstent, Ultraflex) 181, 182, 187, 190, 192, 193, 197, 198. Most metallic stents are available in covered and noncovered versions. No ideal stent is currently available. The type of stent to be used is a matter of debate and is often dictated by availability and individual preference. Most metallic stents can be inserted on an outpatient basis.
Results
Placement of stents leads to an immediate and significant decrease in symptoms and an improvement in respiratory function in 80–95% of the patients. Most of the patients with severe respiratory impairment are able to be discharged following treatment. As results depend on optimal positioning of the prosthesis and some of the stents show a poor visualization under fluoroscopy, new advances in CT fluoroscopy are promising guiding techniques allowing precise and real time control of stent insertion in selected cases.
Complications
Complications are related to the type of stent, and include early or late stent migration (1–19%), infection (3–22%), deformation or breakage (1–36%) and stent obstruction by secretions, granulation formation or tumour overgrowth (6–21%). Other complications, such as major haemorrhage and tracheobronchial fistula are rare. New developments in stent configuration and composition seem to be associated with aneasier introduction and a lower rate of complications.
Conclusion
A close collaboration between interventional radiologists and pathologists, primary care physicians, pulmonologists, medical and radiation oncologists as well as thoracic surgeons is a prerequisite for optimal patient management, offering full therapeutic options. Future developments in imaging based patient management mainly concern oncological applications. Following preliminary studies on percutaneous treatment of inoperable or early non-small cell lung cancer, such as electrochemical polarization of cancer 199, new modalities are emerging including percutaneous brachytherapy 200 and radiofrequency tumour ablation 201. Interventional radiology will also be used for catheter or needle mediated immunomodulatory or gene therapy delivery to the target organs. Concerning stenting procedures, future types of stents include hybrid stents with metallic components and a smooth synthetic covering of silicone or polyurethane, biodegradable stents, chemically and radioactively coated stents 182, 202.
References
