Medical thoracoscopy (pleuroscopy): Diagnostic and therapeutic applications

INTRODUCTION — Thoracoscopy (pleuroscopy) involves passage of an endoscope through the chest wall for direct visualization of the pleura. Medical thoracoscopy is most commonly used for pleural fluid drainage, parietal pleural biopsy, and pleurodesis. Over time the equipment and applications have developed and are similar to those used in video-assisted thoracoscopic surgery (VATS), however medical thoracoscopy is typically more limited in its diagnostic and therapeutic functions and performed by pulmonologists (as opposed to surgeons), thus the term "medical" thoracoscopy. While its use varies among clinicians and countries, this review is limited to its most common applications.

The indications and contraindications for medical thoracoscopy are discussed in this review while the technique, equipment, and complications are discussed separately. (See "Medical thoracoscopy (pleuroscopy): Equipment, procedure, and complications".)

COMMON APPLICATIONS — Medical thoracoscopy is generally a second-line tool for diagnostic or therapeutic procedures of the pleura. It should not replace preliminary diagnostic approaches, including thoracentesis for the evaluation of a pleural effusion.

For patients in whom parietal pleural biopsy is indicated, whether closed needle biopsy should be done before thoracoscopic biopsy is not clearly established and depends upon the suspected underlying diagnosis and other planned procedures. For example, ultrasound-guided needle aspiration of a pleural based mass has an excellent diagnostic yield, but would not offer the ability to simultaneously perform talc poudrage. However, image-guided (ultrasound or computed tomography [CT]) needle aspiration or closed needle (Abrams needle) biopsy may be preferred in cases where thoracoscopy is unavailable or tuberculosis (TB) leads the differential.

While the specimen size has been larger with cryobiopsy compared with flexible forceps biopsy, the diagnostic yield remains similar [1,2]. A randomized study comparing cryobiopsy to flexible forceps biopsy found larger specimens were obtained with cryobiopsy, but with no difference in diagnostic yield or complications [2]. However, rigid forceps biopsies seem to have a larger biopsy sample than both cryobiopsy or flexible forceps biopsy, but with unknown clinical significance [3]. Additional studies will be needed to examine if rigid forceps or cryobiopsy may improve the diagnostic yield for mesothelioma, which often requires a larger and deeper biopsy specimen.

Similarly, for those with pleural effusions in whom chemical pleurodesis is indicated, choosing whether to deliver sclerosant via a chest tube (slurry) or a thoracoscope (poudrage) is unclear and usually depends upon the medical circumstances (eg, medical condition, physical performance status), goals and preferences of the patient, and institutional practice [4]. (See "Management of malignant pleural effusions", section on 'Chemical pleurodesis alone (bedside or thoracoscopic)' and "Management of nonmalignant pleural effusions in adults", section on 'Pleurodesis'.)

Diagnostic evaluation of an exudative pleural effusion of unknown etiology — Medical thoracoscopy is most commonly performed when multiple attempts at thoracentesis (typically two) have failed to achieve a diagnosis in patients with a recurrent exudative pleural effusion. This approach, which is supported by the 2010 British Thoracic Society Pleural Disease Guideline [5,6], is based upon the high diagnostic accuracy of thoracoscopic biopsy in this setting compared with closed needle or image-guided biopsy [7].

Choosing among medical thoracoscopy or video-assisted thoracoscopic surgery (VATS) is dependent upon the complexity of the procedure, the possible need for concurrent minimally invasive surgery (ie, parenchymal lung biopsy, bullectomy, decortication), as well as institutional expertise. Medical thoracoscopy can be safely performed in those who have an uncomplicated pleural space in whom no additional surgery is anticipated while VATS may be preferred in those with a complicated pleural space (eg, multiple adhesions), those in whom concurrent additional surgery is anticipated, or when medical thoracoscopy is not available. (See "Selection of modality for diagnosis and staging of patients with suspected non-small cell lung cancer", section on 'Pleural (T2, T3, M1a)' and "Procedures for tissue biopsy in patients with suspected non-small cell lung cancer", section on 'Suspected pleural metastases' and "Diagnostic evaluation of the hemodynamically stable adult with a pleural effusion".)

The indications and results of medical thoracoscopy vary geographically (table 1), however pleuritis and malignancy are typically the most common diagnoses obtained from medical thoracoscopy. (See "Diagnostic evaluation of the hemodynamically stable adult with a pleural effusion".)

Parietal pleural biopsy is rarely needed for transudative effusions of unclear etiology but may be considered on a case-by-case basis (eg, in amyloidosis). (See "Management of nonmalignant pleural effusions in adults".)

Suspected malignant pleural disease — In patients with suspected malignant involvement of the pleura, medical thoracoscopy allows direct visualization of the pleural surfaces (visceral and parietal) for obvious involvement of the pleural membranes (movie 1). In addition, fluid can be completely drained from the pleural space and biopsies can be taken under direct visualization from involved and uninvolved parts of the parietal, and less commonly, visceral pleural membrane.

Endoscopic characteristics of pleural malignancy include nodules, polypoid lesions, and "candle wax drops" (picture 1 and picture 2). However, mesothelioma can resemble inflammation and be missed [8,9]. A study suggested that visual appearance is often misleading, even to experienced thoracoscopists, and as such, biopsies should be obtained and sent for pathology and microbiologic examination [10].

Although interpreting frozen sections from parietal pleura is challenging, if cancer is found, pleurodesis or placement of an indwelling pleural catheter may be performed thoracoscopically in the same setting. This also gives the advantage of performing chemical pleurodesis as an ambulatory procedure with an indwelling pleural catheter, however, the issue of cost-effectiveness/efficacy for thoracoscopically placed indwelling pleural catheter (with or without pleurodesis) compared with a bedside-placed indwelling pleural catheter (with or without pleurodesis) remains controversial [11,12]. (See "Management of malignant pleural effusions".)

There are several reasons why thoracoscopy may be successful when thoracentesis and/or closed needle biopsy fail to establish the diagnosis [13-15]:

●Cytologic detection of malignant cells requires significant exfoliation of cells from the pleural surface into the pleural fluid, and therefore may be missed in early pleural carcinomatosis or in malignant mesothelioma.

●Metastatic disease of the parietal pleura may be randomly distributed and consequently missed or inaccessible by needle biopsy, compared with thoracoscopic biopsy where tissue is obtained under direct visualization.

In cases where thoracoscopy does not reveal an etiology and the pleural effusion remains or returns, repeat thoracoscopy can be performed without an increase in the duration of the procedure or other morbidity [16].

Metastatic lung cancer — Most effusions from lung cancer result from direct carcinomatous involvement of the visceral pleura with secondary seeding of the parietal pleura or from hematogenous or lymphatic spread. Pleural effusions due to lung cancer (usually non-small cell lung cancer [NSCLC]) represent unresectable disease. Thoracentesis, even when performed multiple times, is nondiagnostic in about one-third of patients with suspected NSCLC, thereby necessitating pleural biopsy. Thoracoscopic biopsy (medical or VATS) in this setting is preferred rather than image-guided or closed needle biopsy since it has a high diagnostic sensitivity (up to 98 percent) and can offer pleural palliation in the same setting. In most cases confirmation of cancer leads to accurate staging and molecular genotyping, resulting in appropriate therapy, and in rare cases when no evidence of pleural cancer is found, it may open up the possibility of curative resection. Data supporting this approach are discussed separately. (See "Selection of modality for diagnosis and staging of patients with suspected non-small cell lung cancer", section on 'Pleural (T2, T3, M1a)' and "Procedures for tissue biopsy in patients with suspected non-small cell lung cancer", section on 'Suspected pleural metastases' and "Diagnostic evaluation of the hemodynamically stable adult with a pleural effusion".)

Mesothelioma — Medical thoracoscopy is being increasingly used for the diagnosis of mesothelioma (movie 2). Repeated thoracentesis has a low sensitivity (<35 percent) and closed needle biopsy specimens are rarely of sufficient size to allow a definitive histologic diagnosis. Even by thoracoscopy, the accuracy of diagnosing mesothelioma may be lower than that for lung cancer due to inadequate visualization due to extensive adhesions or the nonspecific appearance of lesions (affected regions may appear as areas of inflammation) and inherent difficulties in pathological identification of the tumor. In one study, surgical pleural biopsy had only an 81.6 percent concordance on mesothelioma histologic typing compared with subsequent surgical resection. The discordant rate decreased with increasing number of biopsies, 10 or higher tissue blocks had a 100 percent concordance [17].

The historical gold standard for diagnosis of pleural mesothelioma was open biopsy but this procedure is associated with significant morbidity [18]. Thus, in an effort to avoid this morbidity, most experts use thoracoscopy first for diagnosis. While some older studies reported that a diagnosis was established thoracoscopically in 60 to 75 percent of patients with mesothelioma [19-21], newer studies suggest that larger specimen size taken with a 5 mm or 7 mm rigid forceps may be comparable with open biopsy, with yields in the 90 percent range [22]. Some experts use newer instruments including an insulated tip knife (via a semi-rigid thoracoscope) or a cryobiopsy forceps, although the diagnostic accuracy of these tools is uncertain [23,24]. In addition, there has been some investigation using confocal laser endomicroscopy as a real time guidance biopsy tool to improve the diagnostic yield [25]. Location of pleural biopsies may be targeted based on preprocedural imaging using positron emission tomography (PET) scan to optimize results. While the optimal number of biopsies and sampling sites lack standardization, the majority of malignancy in the pleura develops in the lower one-third of the thorax [26]. (See "Presentation, initial evaluation, and prognosis of malignant pleural mesothelioma", section on 'Diagnosis'.)

Suspected benign pleural disease

Tuberculosis — Pleural biopsy (for histologic and microbiologic identification of M. tuberculosis) may be necessary in those in whom a diagnosis of tuberculous effusion cannot be obtained on thoracentesis. Although closed needle biopsy has traditionally been used in the past, thoracoscopic biopsy is now more frequently used and is particularly useful when lysis of adhesions is necessary or when large amounts of tissue are necessary for culturing M. tuberculosis to determine drug resistance, or when expertise for closed pleural biopsy is unavailable. However, many of the areas endemic for TB do not have the availability of medical thoracoscopy. (See "Tuberculous pleural effusion", section on 'Diagnosis'.)

The thoracoscopic appearance of tuberculous pleuritis is usually that of extensive grayish-white granulomas involving the parietal pleura. Significant adhesions may be found in the costovertebral angles (picture 3). At other times, the appearance is simply that of patchy inflammation.

Data to support thoracoscopic rather than closed needle biopsy are limited. In an older prospective study of 100 tuberculous effusions, thorascopic diagnosis was possible in 94 percent of cases compared with 38 percent on closed needle biopsy [27]. In another study, the yield on thoracoscopic biopsy was 100 percent compared with closed needle biopsy (79 percent) [28].

Other benign pleural disorders — If appropriate pleural fluid studies are nondiagnostic, thoracoscopic biopsy may help establish the diagnosis of benign diseases and, more importantly, exclude malignancy.

●Hyaline and calcified asbestos pleural plaques have distinctive endoscopic characteristics, appearing smooth and white. Direct biopsies are difficult to obtain because of the extremely hard consistency of these plaques (image 1). (See "Asbestos-related pleuropulmonary disease".)

●In rheumatoid pleural effusions, the visceral surface usually shows nonspecific inflammation, and the parietal surface has a "gritty" appearance [29]. Many small vesicles or granules can be identified on the parietal pleura. (See "Overview of pleuropulmonary diseases associated with rheumatoid arthritis", section on 'Pleural disease'.)

Chemical pleurodesis for recurrent pleural effusion — Medical thoracoscopy can be used to perform chemical pleurodesis, most often with talc, for recurrent malignant or benign pleural effusions. Details regarding chemical pleurodesis including agent selection, choosing talc insufflation (via thoracoscopy) or slurry via a chest tube, and complications are discussed separately. (See "Chemical pleurodesis for the prevention of recurrent pleural effusion".)

Pleurodesis via medical thoracoscopy is generally well tolerated. The recovery of patients postpleurodesis by medical thoracoscopy is typically five to seven days, which is comparable with other methods of pleurodesis [30-32].

UNCOMMON APPLICATIONS — Medical thoracoscopy is rarely used in the United States for visceral pleural or lung biopsy, blebectomy, pleural abrasion, drainage of a complicated parapneumonic effusion, foreign body removal, or sympathectomy, although practice in Europe may differ in this regard and variations among clinical practice exist. Video-assisted thoracoscopic surgery (VATS) has a well-established role in the performance of these procedures since they are in general more complicated, more invasive, and may require additional interventions for complications such as air leak or hemorrhage and need deeper anesthesia than that typically provided during medical thoracoscopy. (See "Overview of minimally invasive thoracic surgery" and "Anesthesia for video-assisted thoracoscopic surgery (VATS) for pulmonary resection".)

Lung biopsy for parenchymal disease or peripheral nodules — Thoracoscopic lung biopsy is sometimes considered when less invasive techniques, such as bronchoscopy with transbronchial biopsy, bronchoalveolar lavage, fine needle aspiration biopsy, or cryobiopsy, have failed to establish a diagnosis [33-40]. Medical thoracoscopic lung biopsy can help establish the diagnosis of diffuse pulmonary disease, pulmonary infiltrates, or peripheral lesions of unknown cause. In addition, it can provide tissue for microbiologic or mineralogic studies, when either pulmonary infection or pneumoconiosis is being considered. The main advantage compared with bronchoscopy is that thoracoscopy provides larger biopsy specimens and the biopsy can be directed to abnormal areas. (See "Role of lung biopsy in the diagnosis of interstitial lung disease".)

Compared with VATS, data are limited to support the use of medical thoracoscopy in this setting. Two older retrospective studies reported a sensitivity that ranged from 70 percent for localized peripheral lesions to 100 percent for diffuse lesions [33,36]. In a retrospective study of 118 samples from 24 consecutive patients with interstitial lung disease, biopsy findings plus clinical and radiologic data revealed a relevant diagnosis in 75 percent of patients [41].

Although one concern is that hemorrhage and air leak may be more difficult to manage with medical thoracoscopy compared with VATS, limited data suggest that these complications are negligible if the biopsy site has been adequately secured with staples or cautery [33]. Another study reported successful lung biopsy with excellent hemostasis and no air leakage in 18 patients using a cryoprobe to seal the forceps biopsy site [39].

Blebectomy and/or pleurodesis for pneumothorax — In patients with pneumothorax, blebs and bullae are more readily detected and treated using VATS. However, in some centers, medical thoracoscopy is occasionally performed for this indication. (See "Pneumothorax in adults: Epidemiology and etiology" and "Treatment of secondary spontaneous pneumothorax in adults".)

Common findings in those with pneumothorax during standard white light thoracoscopy include a normal appearance (39 percent of patients), small (<2 cm) blebs on the pleura (31 percent), large (≥2 cm) blebs (17 percent), and pleural adhesions (11 percent) [42]. Although rarely done, fluorescein-enhanced autofluorescence thoracoscopy (FEAT) enhances traditional white light thoracoscopy, with many high grade blebs detected by FEAT in areas that appear normal during white light thoracoscopy, and also shows "pleural porosity," (ie, leaky visceral pleura away from areas of blebs and bullae) [43]. This later concept highlights the importance of pleurodesis, in the management of pneumothorax.

In general, small (<2 cm) blebs can be successfully obliterated by medical thoracoscopy via argon beam coagulation, neodymium-doped yttrium aluminum garnet (Nd:YAG) laser, or electrosurgery. This is typically followed by pleurodesis, which can be accomplished mechanically (eg, pleural abrasion), chemically (eg, instillation of talc), or by laser coagulation of the pleura [44].

Patients with large (≥2 cm) blebs or bullae require open surgical or VATS resection. Open surgical bullectomy is still preferred for extensive bullous disease, but VATS is often used to treat less extensive disease. Medical thoracoscopy is seldom used to treat large blebs or bullae, although treatment with thoracoscopic talc poudrage has been reported [45].

Drainage for complicated parapneumonic effusion and empyema — In patients with complicated parapneumonic effusions and empyema, an interventional procedure in addition to chest tube drainage may be required to completely remove infected pleural fluid. The role of medical thoracoscopy in the management of empyema is controversial since reports are mixed and lysis of adhesions can be challenging. Until this role is clarified, chest tube drainage (with or without rTPA and DNase) and/or VATS (when chest tube drainage is insufficient) is the approach of choice. The management of parapneumonic effusions and empyema are discussed in detail separately. (See "Epidemiology, clinical presentation, and diagnostic evaluation of parapneumonic effusion and empyema in adults".)

The use of medical thoracoscopy in this setting has been reported. In a small randomized study comparing medical thoracoscopy and rTPA/DNase, medical thoracoscopy had a significantly shorter hospitalization after the procedure and similar secondary outcomes in terms of failure and complication rate [46]. In a series of 127 patients with empyema, medical thoracoscopy successfully drained the pleural space of 91 percent of patients [47]. However, 49 percent required postprocedure intrapleural fibrinolytic therapy over the ensuing three to five days. In another series of 29 patients, the majority (79 percent) were successfully managed with single-trocar thoracoscopy [48]. Another series reported similar success rates (85 percent) with medical thoracoscopy, particularly when effusions were free-flowing or multiloculated but less effective for those with organized empyema [49].

Foreign body removal — Two cases of removal of a needle in the pleural space by medical thoracoscopy with the rigid instrument have been reported [50]. It was felt the size and firmness of the rigid equipment was better suited for this purpose than the semi-rigid thoracoscope. (See "Medical thoracoscopy (pleuroscopy): Equipment, procedure, and complications", section on 'Instruments'.)

Sympathectomy — Medical thoracoscopy has been used to perform sympathectomy for palmar hyperhidrosis [51]. However, this requires expertise and should only be performed in specialized centers and with thoracic surgery support. (See "Primary focal hyperhidrosis", section on 'Sympathectomy'.)

PROCEDURES NOT GENERALLY PERFORMED BY MEDICAL THORACOSCOPY — Complex minimally invasive thoracic surgical procedures are not generally performed by medical thoracoscopy but are reserved for surgeons skilled in video assisted thoracic surgery (VATS). (See "Overview of minimally invasive thoracic surgery".) Some examples include:

●Lobectomy or pneumonectomy

●Pleurectomy or decortication

●Resection of benign or malignant peripheral pulmonary nodules

●Esophagectomy

●Transthoracic vagotomy

●Creation of a pericardial window

●Repair of a bronchopleural fistula

●Evaluation of mediastinal tumors or lymphadenopathy

CONTRAINDICATIONS — Contraindications to thoracoscopy are similar to those of bronchoscopy (eg, coagulopathy, severe cardiorespiratory compromise) and sedation and anesthesia. (See "Flexible bronchoscopy in adults: Indications and contraindications", section on 'Contraindications' and "Evaluation of perioperative pulmonary risk" and "Preoperative evaluation for anesthesia for noncardiac surgery".)

Specific to thoracoscopy, contraindications include the inability to enter the pleural space due to a fused or complex pleural space (eg, extensive pleural adhesions), hypercapnia/acute respiratory distress or hemodynamic instability, inability to lay supine or in the decubitus position, inability to tolerate a pneumothorax, morbid obesity, and occasionally uncontrolled cough [52]. However, it may need to be considered that dyspnea or inability to tolerate a decubitus position due to a pleural effusion alone may be relieved by the procedure. The change in gas exchange from sedation depends on the quantity and medication chosen; in some cases only local anesthetic may be required to safely perform medical thoracoscopy [5].

SUMMARY AND RECOMMENDATIONS

●Thoracoscopy (pleuroscopy) involves passage of a camera through the chest wall for direct visualization of the pleura. Medical thoracoscopy is most commonly used for pleural fluid drainage, parietal pleural biopsy, and pleurodesis. Although the equipment and some applications are similar to those used in video-assisted thoracoscopic surgery (VATS), it is typically more limited in its diagnostic and therapeutic functions and performed by pulmonologists, thus the term "medical" thoracoscopy. (See 'Introduction' above.)

●The most common indication for medical thoracoscopy is the acquisition of parietal pleural biopsy in patients with recurrent exudative pleural effusion. This approach is based upon the high diagnostic accuracy of thoracoscopic biopsy in this setting compared with closed needle or image-guided biopsy [7]. Choosing between medical thoracoscopy or VATS is dependent upon the complexity of the planned procedure, the possible need for concurrent minimally invasive surgery, as well as institutional expertise. Diagnostic yields are best for malignant pleural effusion (sensitivity up to 98 percent) and tuberculosis (94 to 100 percent) and lower for mesothelioma (75 to 90 percent). (See 'Diagnostic evaluation of an exudative pleural effusion of unknown etiology' above.)

●Medical thoracoscopy can also be used to perform chemical pleurodesis, most often with talc, for recurrent malignant or benign pleural effusion. (See 'Chemical pleurodesis for recurrent pleural effusion' above and "Chemical pleurodesis for the prevention of recurrent pleural effusion".)

●Medical thoracoscopy is rarely used for lung biopsy, blebectomy, pleural abrasion, drainage of a complicated parapneumonic effusion, foreign body removal, or sympathectomy, although practice may differ among clinicians and regions in this regard. VATS has a well-established role in the performance of these procedures since they are in general more complicated, more invasive, and may require additional interventions for complications such as air leak or hemorrhage and need deeper anesthesia than that typically provided during medical thoracoscopy. (See 'Uncommon applications' above.)

●Complex minimally invasive thoracic surgical procedures are not generally performed by medical thoracoscopy but are reserved for surgeons skilled in VATS. These include lobectomy, pneumonectomy, pleurectomy, decortication, wedge resection, vagotomy, esophagectomy, pericardial window, bronchopleural fistula repair, and evaluation of mediastinal tumors or lymphadenopathy. (See "Overview of minimally invasive thoracic surgery".)

●The major contraindication to medical thoracoscopy is a fused pleural space and extensive pleural adhesions. (See 'Contraindications' above.)

ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Francis Sheski, MD, who contributed to earlier versions of this topic review.