Medical Thoracoscopy

Introduction

Medical thoracoscopy is both a diagnostic and therapeutic pleural procedure to visualize the pleural space, obtain biopsies, and in certain cases perform localized interventions. It may be performed safely in either an inpatient or outpatient setting, requiring only moderate sedation, local anesthesia, and a small amount of analgesia. It offers a minimally invasive alternative to video-assisted thoracoscopic surgery (VATS). Medical thoracoscopy is sometimes referred to as pleuroscopy and is most often performed in the setting of undiagnosed exudative effusions, malignant pleural effusions, or recurrent pneumothorax. It is frequently considered when pleural uid analysis and cytology from thoracentesis fail to identify the etiology of a recurrent, exudative pleural effusion. Worldwide, medical thoracoscopy is considered the gold standard for the diagnosis of tuberculous pleural effusions with a high degree of safety and effcacy. It is also highly sensitive and specifc for the diagnosis of malignant pleural effusions, while also achieving a high rate of pleurodesis when chemical pleurodesis is performed.

The very frst case report of medical thoracoscopy dates back to 1866 when Richard

M. Tukey (*) · K. Van Nostrand · G. C. Michaud Pulmonary, Critical Care and Sleep Medicine, University of South Florida, Tampa, FL, USA e-mail: melissatukey@usf.edu; keriannv@usf.edu

Cruise described his single patient experience. Hans Christian Jacobeus further developed the technique in the early 1900s and is considered the “father” of medical thoracoscopy. In the pre-­ antibiotic era, medical thoracoscopy was primarily used in the management of infectious pleural effusions, particularly tuberculous effusions, but its use declined with the discovery and optimization of antibiotic regimens. Interest in the procedure was renewed when Roche and his colleagues frst described the use of medical thoracoscopy to achieve pleurodesis by instilling talc into the pleural space in 1963. Interestingly, these procedures were mainly performed by pulmonary physicians until the early 1990s when thoracic surgeons adapted these techniques along with advances in abdominal laparoscopic surgery to the thorax [1]. No data exists regarding the exact prevalence of the use of medical thoracoscopy around the world, although variation may mirror the prevalence of diseases for which it is commonly performed, such as malignancy and tuberculosis (TB), and with the availability of other expertise such as video-assisted or robotic-­thoracic surgery. According to a survey of US pulmonology training programs published in 2005, only 12% of programs offered training in medical thoracoscopy [2]. The availability of the procedure is thought to be much more widespread in Europe, as many of the pioneers and champions of this procedure are European.

Diagnostic Approach to Pleural Efusions

The initial step in the management of nearly all pleural effusions is diagnostic and/or therapeutic thoracentesis. Light and his colleagues classifed pleural effusions into the diagnostic categories of exudates and transudates based on the pleuraluid composition obtained via thoracentesis [3]. Transudative effusions are defned as having low pleural to serum ratios of protein and lactate dehydrogenase (LDH) and are often associated with conditions leading to increased hydrostatic pressure such as heart failure, liver or renal disease. On the other hand, exudative effusions are defned by the presence of elevated pleural to serum ratios of total protein (>0.5) and/or LDH (>0.6 or pleural LDH >2/3 the upper limit of the normal serum value). The differential diagnosis of exudative effusions remains broad. Worldwide the most common causes are infections, including tuberculosis, and malignancy. Light’s classifcation system, developed nearly 50 years ago, has been widely criticized as the results may be in uenced by manipulation of the pleural space either mechanically or chemically. Disruption of the pleural space results in localized in ammation which may change the cellular and biochemical makeup of the pleural uid. In addition, diuretic therapy may alter the pleural uid composition resulting in the misclassifcation of a transudate as an exudate. Although the purpose of classifying pleural effusions as transudative and exudative is to limit the differential diagnosis and mitigate patient risk from futile diagnostic testing, it must also be noted that approximately 10% of transudative effusions may be malignant and necessitate appropriate evaluation [4]. There are a few plausible explanations as to how a malignant effusion could be meet diagnostic criteria of a transudate. Early malignant effusions may simply be the result of the tumor causing obstruction of the lymphatics as opposed to frank invasion or tumor emboli to the pleura. The other consideration is that the cancer patient may have a concomitant medical issue leading to a transudative pleural effusion such as pulmonary edema. In the setting where there is a high pre-test prob-

ability of malignancy, further evaluation of the pleural space with medical thoracoscopy in transudative effusions should be considered.

Medical thoracoscopy is a powerful tool in the diagnostic evaluation of undiagnosed or what are commonly called “unclear” exudative effusions. An unclear exudate is defned as an effusion meeting Light’s Criteria for an exudate, but the etiology remains unidentifed after initial routine evaluation including imaging, thoracentesis for cytology, microbiology and biochemistries, as well as special tests for certain populations. Approximately 15% of exudative effusions are categorized as unclear exudates [5]. These effusions require additional diagnostic testing, particularly to exclude malignancy. Although it is commonly believed that pleural uid appearance predicts malignancy, a recent study has demonstrated that bloody appearance is not necessarily indicative of malignancy [6]. The sensitivity of thoracentesis for malignancy is unfortunately only 40% for the initial specimen, rising to around 70% with 3 consecutive thoracenteses [7]. The procedures with high sensitivity and specifcity for diagnosing malignancy include closed pleural biopsy, medical thoracoscopy, and VATS. Computed tomography (CT)-guided biopsy is also a consideration; however, this procedure is often limited by access to the procedure, risk of pneumothorax, bleeding, and technical aspects related to movement particularly when lesions are near or on the hemidiaphragm. With respect to closed pleural biopsy, it can readily be done at the bedside; however, relatively few practicing pulmonologists or even newer generation interventional pulmonologists have much experience with this procedure. In a 2005 survey of pulmonary and critical care program directors, only 48% of programs stated that their fellows performed the requisite fve procedures considered the minimal standard for competence [2]. Interestingly, in a similar survey of interventional pulmonology fellowships nearly a decade later, closed pleural biopsy is not mentioned as a core competence [8]. In a systematic review and meta-analysis of studies comparing the sensitivity and specifcity of closed pleural biopsy compared with medical thoracoscopy,