Medical thoracoscopy was initially performed in 1910 by an internist from Sweden, Hans-Christian Jacobaeus. Jacobaeus was the first to use the term thoracoscopy, which he described as "replacing fluid with air" in order to examine the pleural surfaces of two patients with tuberculous pleurisy. Jacobaeus later developed a therapeutic application for thoracoscopy by using thermocautery to lyse adhesions and create a pneumothorax to treat tuberculosis. 
During the 1950s and 1960s, thoracoscopy gained popularity with pulmonologists because of the tuberculosis endemic in the United States. The major indications were for pleural and pulmonary biopsies for diffuse lung disease. However, with the advent of effective chemotherapy for tuberculosis, the need for thoracoscopy decreased. The procedure was later adopted by surgeons after advances in optics, laparoscopic techniques, and video technology. Thoracoscopy grew into the video-assisted thoracoscopic surgery that is currently performed by thoracic surgeons.
The term thoracoscopy is confusing because it refers to both the medical and surgical procedures. To avoid confusion, some authors suggest that medical thoracoscopy should be referred to as pleuroscopy. The term thoracoscopy may be used exclusively for the surgical thoracoscopic procedure.
The accepted indications for medical thoracoscopy include the following:
Workup and diagnosis of idiopathic pleural effusions
Staging of lung cancer
Site-directed biopsy of parietal pleura
Staging for mesothelioma
Idiopathic pleural effusions that have been sampled by thoracentesis are ideal for medical thoracoscopy. The direct visualization of the pleura allows for site-directed biopsy of abnormal parietal pleura. Additionally, it allows for examination of the visceral pleura and any clues that may provide towards the diagnosis of the pleural effusion. Currently, most interventional pulmonologists limit biopsy to the parietal pleura due to the risk of injury to the lung when sampling the visceral pleura.
Pleural Effusion of Unknown Origin
Cytologic examination of pleural fluid is only diagnostic in 60-80% of patients with metastatic pleural involvement and in less than 20% in patients with mesothelioma.  In cases for which the initial evaluation of a pleural effusion is nondiagnostic and malignancy is suspected, medical thoracoscopy and parietal pleural biopsy should be considered. Medical thoracoscopy with pleural biopsy, as shown in the image below, establishes a diagnosis in more than 90% of the cases. 
Malignant Pleural Effusion/Pleurodesis
In cases with an established malignant diagnosis, medical thoracoscopy also has a therapeutic role in the form of pleurodesis. Complete evacuation of pleural fluid, with maximization of lung expandability by removing adhesions and pleurodesis by talc insufflations (see the image below), has short- and long-term success rates greater than 90%. 
The benefit of the pleurodesis is twofold. First, it improves the patient’s functional status and quality of life. In the setting of advanced malignant disease, this is the central goal of any physician. In patients who are undergoing further treatment for malignancy, there is an added benefit of increasing treatment options by improving the patient’s functional status.
In addition, patients who do require further treatment can be excluded from certain chemotherapeutics because of the chemotherapy’s tendency to distribute into the pleural effusion and affect serum levels. The classic examples of this are methotrexate, fludarabine, and possibly pemetrexed. [4, 5, 6]
Survival of patients with advanced pleural disease is often discussed in weeks to months. The benefits of medical thoracoscopy against repeated thoracentesis should be carefully considered for the individual patient.
In the patient with known lung cancer and an effusion with a negative cytology, medical thoracoscopy is an excellent tool. It allows for direct visualization of the pleura and a thorough examination for evidence of metastasis (see the images below).
The sensitivity of pleuroscopy-guided biopsy in malignant pleural effusions is 95%, compared to 62% for cytology from thoracentesis and 44% for closed pleural biopsy.  By allowing for more accurate diagnosis and staging, this may help prevent unnecessary procedures on a patient who is inappropriately categorized into a lower stage.
The yield of cytology for malignant mesothelioma is even lower than most malignant effusions, as low as 41% in one study.  It can be difficult to reach a definitive diagnosis without complete visualization of the pleural space. Medical thoracoscopy is favored over thoracotomy for two reasons. First, the pleural specimen obtained with the minimally invasive 5-mm forceps is comparable to the specimen achieved with open biopsies. Second, the site-directed nature of pleural biopsies through the semirigid pleuroscope allows a minimally invasive approach.
Tuberculous Pleural Effusion
There is controversy whether medical thoracoscopy is warranted when the suspicion for tuberculosis is high. In these cases, the diagnostic yield from closed-needle pleural biopsy is approximately 69%, with some studies reporting rates as high as 88%.  The current consensus is that medical thoracoscopy should be reserved for special circumstances, such as lysis of adhesions or more effective drainage of loculated effusions, as well as when larger quantities of tissue are needed for sensitivities. 
Recurrent Pleural Effusions of Benign Origin
Recurrent pleural effusions are often caused by heart failure, cardiac surgery, nephritic syndrome, connective tissue diseases, and other inflammatory disorders. When these effusions are not controlled by repeat large-volume thoracentesis, pleural biopsies can be obtained through medical thoracoscopy and pleurodesis can be performed if necessary.
Empyema and Complicated Parapneumonic Effusions
Some interventional pulmonologists have used medical thoracoscopy for drainage of uncomplicated empyema and chest tube placement. Additionally, it can be used carefully for lysis of thin fibrous adhesions (see the image below). 
Currently, this is not routinely performed or the standard of care, mainly because timing is key in these procedures and they should be considered early if chest tube drainage is inadequate. [3, 10] In later phases of the empyema, there may be thick fibrous adhesions, pleural peel, or trapped lung. In these cases, early video-assisted thoracoscopic decortication is required. [11, 12]
Medical thoracoscopy can offer definitive treatment or diagnostic inspection of a patient with a recurrent pneumothorax. In patients who are not candidates for video-assisted thoracoscopic surgery, pleural abrasion or talc pleurodesis can be performed. For patients suitable for video-assisted thoracoscopic surgery, bullectomy, pleural abrasion, and pleurectomy in the operating room are superior and preferred. 
The major contraindications are related to the ability to perform the procedure. As long as no contraindication exists for the ability to insert instruments into the pleural space, it can be performed safely. Even when the lung is adherent to the chest wall, the use of transthoracic ultrasound by interventional pulmonologists can allow identification of safe areas to insert the trocar and pleuroscope.
A pleural separation of at least 10 mm is recommended to minimize injury to the lung. In patients with small effusions, a pneumothorax may need to be induced by cannulating the pleural space and asking the patient to inspire deeply while the catheter is open to the atmosphere. The presence of a pneumothorax can then be confirmed with either chest radiograph or thoracic ultrasound at the bedside. This procedure is limited by the ability of the patient to tolerate a pneumothorax. In patients who already have an effusion, the concern regarding tolerance of a pneumothorax is not as worrisome because an equal volume of fluid would be replaced by air.
The following relative contraindications may be corrected and accounted for:
There are two different pleuroscopes: the rigid and the semirigid pleuroscopes. The choice of instrument depends on the indication of the procedure. Most procedures will be performed with a semirigid pleuroscope for the above-mentioned indications. The main indications for the use of a rigid pleuroscope involve trapped lung, lysis of thick adhesions, empyema, and pneumothorax.  These patients may be referred to a thoracic surgeon for a video-assisted thoracoscopic surgery.
The semirigid pleuroscope is similar to a video bronchoscope. It consists of a handle with a shaft that measures 27 cm in length and 7 mm in diameter, as shown in the image below.
The first 22 cm of the pleuroscope is rigid, with an additional 5-cm flexible scope on the distal end. The flexible end is operated through a level on the handle, similar to a flexible bronchoscope. The 2.8-mm working channel accommodates instruments such as biopsy forceps and needles.
The rigid pleuroscope includes a xenon light source, an endoscopic camera that transmits to the eyepiece of the telescope, and a video camera. It provides different angles of vision, both direct and oblique (30-50 degrees). The trocars come in different size diameters (3-13 mm). The traditional size of the forceps by which to obtain biopsies is 5 mm. However, 3-mm biopsy forceps have a yield similar to conventional forceps.
Medical thoracoscopy is generally performed in an endoscopy suite. Moderate sedation with local anesthesia is used in a manner similar to inserting a chest tube in a conscious patient. Epinephrine can be added to the lidocaine to minimize bleeding at the trocar insertion site.
Patients are placed in the lateral decubitus position with the involved side up, as shown in the image below.
A round bolster is placed under the thorax when patient is in position to arch the vertebral column upward to maximize the intercostal spaces of the involved side. To further widen the intercostals spaces, the patient’s arm is placed at a right angle to the body. On very rare occasions, a dorsal decubitus position or a ventral decubitus position is used. 
Monitoring & Follow-up
Because of the minimally invasive nature of the procedure, many patients can be discharged the same day. In most cases, total resolution of the pneumothorax occurs within minutes. After a chest radiograph confirms the re-expansion of the lung, the chest tube is often removed while the patient is still in the procedure room.
Complications of medical thoracoscopy are rare. The mortality risk is 0.09%, with a major complication rate of 1.9% and a minor complication rate of 5.6%.  Complications with a rigid scope include prolonged air leak, hemorrhage, subcutaneous emphysema, postoperative fever, empyema, and seeding of chest wall from mesothelioma. Bleeding after a parietal pleural biopsy, lung perforation, and infections are the most prevalent complications about which the interventional pulmonologist is most concerned. In the case of pleurodesis, 30% of patients develop low grade fevers and may require short term hospitalization for observation.
To prepare for the procedure, the pulmonologist can remove 500 ml of fluid from the pleural space through thoracentesis and induce a pneumothorax before inserting a trochar. Alternatively, the pulmonologist can make an intercostal incision that allows fluid to be aspirated freely once the trocar is inserted.
If malignancy is suspected, a single skin incision is made in approximately the fifth to seventh intercostal space along the lateral chest wall of the involved hemithorax. Pleural fluid is evacuated and pleural biopsies are obtained of the pleura. If the procedure is performed to visualize blebs and bullae in the lung apex, an incision in the fourth intercostal space is preferred.
Medical thoracoscopy is usually performed with a single-puncture technique, but can also use a double-puncture technique. For both, the pulmonologist visualizes the pleural space with a rigid or semirigid pleuroscope. Once the pleural cavity is entered, almost complete visualization of the parietal cavity is possible; only the posterior and mediastinal side of the lung cannot be seen.
With the single-puncture technique, the pulmonologist inserts accessory instruments through the working channel of the pleuroscope. Parietal pleural biopsies, for example, can be done using illuminated forceps through a single point of entry. To enter the pleural cavity, an 8- to 10-mm skin incision is made parallel with and centered in the intercostal space selected. Blunt dissection is then performed with a straight scissor down to the parietal pleura. The trocar is gently pushed through the dissected pathway; with moderate pressure, it is pushed through the pleura (see the image below).
Any fluid remaining in the pleura is aspirated with a blunt flexible tube that is fed through the trocar sleeve. The tube is usually smaller than the track made into the pleural space to continue to allow for air to enter the thoracic cavity and induce a pneumothorax.
The insertion of the semirigid pleuroscope through the trocar is shown in the image below.
With a double-puncture technique, the operator makes a second smaller incision along another intercostal space, which allows for insertion of a pleural trocar for accessory instruments. The second trocar is smaller, only 5 mm, and therefore only requires a 5-mm incision. The double-puncture technique is usually used when there is a need to lyse severe adhesions, control bleeding, suction large amounts of pleural fluid, or perform biopsies of the visceral pleura.
For parietal pleural biopsies, both abnormal- and normal-appearing pleura are sampled. Typically 4-6 biopsies of a suspicious lesion will establish a diagnosis. When malignancy is suspected and the endoscopic findings have been nonspecific, the number of biopsies should increase to 10-12 biopsies. 
When the procedure is complete, a chest tube is inserted through the original incision site. The lung is gently re-expanded by connecting the chest tube to a suctioning device. In the case of a trapped lung, the operator has the option of placing a normal chest tube with or without suction or placing a tunneled chest drain for outpatient management.