Lung anatomy

There are 3 lobes in right lung and 2 lobes in left lung. The lobes are separated by fissures. There is oblique fissure separating lower lobe from upper and middle lobes on the right, running in the level of 6^th rib. Horizontal fissure originates from the previous at mid-axillary line and parallels the 4^th rib. On the left, there is just oblique fissure at the corresponding level of 6^th rib. Nevertheless, lung anatomy is variable and so may the fissures vary. Visceral pleura covers the lungs and, covering the hila and creating pulmonary ligament, it traverses to the parietal pleura.

Lung segments with their tertiary hila are another important anatomical units. There are 10 segments on the right and 8 segments on the left in most cases, instead of the original 10. Because segments 1+2 on the left usually have common artery and segmentary bronchus and because medial basal segment is frequently missing or joined to the anterior basal segment, there are only 8 segments on the left.

Bronchial tree starts under the larynx with trachea at the level of C6 vertebral body. It is 10 to 13 cm long and its lumen is held by 15 to 20 C-shaped cartilages. There is only soft membranous wall dorsally. In the level of Th 4-5 it divides into right and left main bronchi. The right bronchus is shorter, wider and steeper and further subdivides into 3 lobar bronchi. The left bronchus runs almost horizontally and gives rise to 2 segmental bronchi. The bronchial tree anatomy tends to be pretty constant.

This is the cranio-caudal position of anatomical structures in the hila: main bronchus, pulmonary artery, pulmonary veins in the right and pulmonary artery, main bronchus and pulmonary veins in the left.

Nutritional bronchial branches run of aorta, right bronchial veins empty to azygos vein and left bronchial veins empty to hemiazygos vein and intercostal veins.

Mountain-Dressler map of chest lymph nodes stations serves to precisely distinguish different perioperatively biopsied nodes and helps in proper oncological staging (N1-N3).

Surgical approaches

Antero-lateral or posterolateral thoracotomies are used commonly. Vertical muscle sparing thoracotomy is a convenient approach for smaller resections like metastasectomies. The incision spares thoracis wall muscles, particularly the latissimus dorsi muscle. Clamshell thoracotomy consists of bilateral anterolateral thoracotomies interconnected by transverse sternotomy and offers very wide approach to both pleural cavities and mediastinum. Thoraco-phreno-laparotomy can be used in surgeries of esophagus or large hiatal hernias. This incision opens left pleural and peritoneal spaces and includes the incision of diaphragm.

Mini-invasive techniques with small incisions and trocars for camera and endoscopic instruments include videothoracoscopy (VTS) and video-assisted thoracoscopic surgery (VATS). The later adds a small thoracotomy (4cm). Nowadays, every thoracoscopic surgery is referred to as VATS. In some cases, only one short incision is used (uniportal VATS). Some experts use sub-xiphoideal approach. Surgical robot can be used for thoracic procedures as well (robot-assisted thoracoscopic surgery, RATS).

Other specialized thoracic approaches are used on rare occasions, Darevell-Grunenwald approach to thoracis outlet is an example.

Extracorporeal membrane oxygenation (ECMO) may be use in specific circumstances in thoracic surgery. Those include lung transplantation surgery and contralateral lung resection, substituting the remaining lung parenchyma insufficiency in oxygenation. Venous blood is pumped into the ECMO machine from venae cavae or right atrium and blood gasses are exchanged. Blood outflow can either be connected to arterial blood stream (substituting both heart and lungs) or to venous blood stream (substituting lungs only).

Lung resection

There are anatomical and extraanatomical resections. Anatomical resections include segmentectomy (dividing segmental artery, vein and bronchus), lobectomy and bilobectomy (dividing lobar structures) and pneumonectomy (removing whole lung), which is indicated in advanced, central or hilar lung cancer. Transpericardial pneumonectomy is a variant. Pneumonectomy is a high-risk procedure, with bronchopleural fistula as the most serious complication. Sleeve resection of bronchus or blood vessels may be performed in the case of central growth of the tumor. Wedge shaped excision of the infiltrated structure is reconstructed with bronchoplasty or angioplasty.

Extraantomical resections like lung wedge resection, enucleation (or precision excision) are used in metastasectomy and resection of bulae.

Every planned lung parenchyma removal requires preoperative spirometry to evaluate patient’s ventilation reserve and oxygenation capacity. Excess lung resection may lead to ventilator dependency. Spiroergometry is even better in estimating ventilation functions.

Diagnostic tools

We start with thorough history and clinical exam (see medical propedeutics). Other exams follow. Plain chest x-ray is far the most common. It displays rough pathology like pneumothorax or fluidothorax, but it is insufficient for mass lesions. Contrast enhanced computed tomography (CT) is a gold standard exam and enables evaluation of all anatomical structures. Further tests are guided by the precluded pathology. Ultrasonography helps in measuring intrapleural fluid extent and volume and in guiding its drainage. Aspired fluid is sent for wide analysis (biochemical, microbiological, TB tests, cytology). Bronchoscopy has its invasive and imaging modalities. We can perform bronchoscopic needle of forceps biopsy, brush cytology or lavage. Endobronchial ultrasonography (EBUS) can evaluate surrounding lymph nodes and guide further transbronchial needle biopsy. Magnetic resonance imaging (MRI) is useful to depict relation of chest wall tumors to the surrounding anatomical structures. PET/CT may be used for staging of malignant disease. Small lesions (>1cm), however, are not displayed by PET and may be missed. On the other hand, PET-positive mediastinal lymph nodes may be inflammatory and therefore falsely over-stage the disease. VTS and video-mediastinoscopy are the most invasive diagnostic methods and allow for biopsy where unenhanced CT guided biopsy or other methods are not applicable.

Lung disease

Some of the pathology is listed only, please refer to pneumology and pathology textbooks for details. Congenital conditions: agenesis, hypoplasia, aplasia, tracheal and bronchial abnormalities, congenital lobar emphysema, lung sequestration. Inflammatory conditions: pneumonia, lung abscess, bronchiectasia, tuberculosis. Interstitial conditions: emphysema, atelectasis. Others: chronic bronchitis, asthma, COPD, ARDS, vascular disease, lung oedema.

Lung cancer

There are benign and malignant tumors, the later may be primary or secondary.

1)    Benign tumors

a.     epithelial – papilloma, adenoma, bronchial cystadenoma

b.     mesenchymal – fibroma, lipoma, leiomyoma, chondroma, granulocelular tumor, sclerosing hemangioma, fibrous histiocytoma, hamartoma.

2)    Malignant tumors – splinocelular, adenocarcinoma (either conventional or bronchio-alveolar), large-cell carcinoma, small-cell carcinoma, carcinoid

3)    Secondary malignant tumors (lung metastasis) – colorectal, renal, gynecological, sarcomas, melanomas. See pathology for details.

In Czech republic, lung cancer resides 2^nd place in incidence after colorectal cancer. There were 6782 new cases reported (C33-C34 ICD diagnoses) in 2016. The incidence is 86,2/100000 and 42,9/100000 in men and women respectively. It is dropping in men, but raising in women. Five-year survival slightly exceeds 10%. Only 14% cases are amenable for surgical treatment at the time of diagnosis. The incidence increases after 55 years of age and most cases are diagnosed in 60-69 age group.

Active and passive tobacco smoking accounts for most cases, the smoker/non-smoker ratio is 9:2. Exposition to radon, arsenic, nickel, sulfur, chromium, asbestos, ionizing radiation, chemical carcinogens and preexisting lung disease and family history of malignant disease are additional risk factors. Poor prognosis is mostly based on late diagnosis, early stages are mostly asymptomatic. High-risk patients should therefore be screened with low-dose CT.

Symptoms and signs can be subdivided into 3 groups:

-        Intrathoracic – new onset of chronic cough or changes in already present chronic cough, recurrent pneumonia, hemoptysis, dyspnea (caused by the actual tumor or malignant pleural effusion), chest pain, superior vena cava syndrome, hoarseness, dysphagia, secondary anemia and weight loss. Apical neoplasia (Pancoast tumor) may invade brachial nerve plexus causing arm pain or sympathetic nerves causing Horner sign. This so-called Pancoast syndrome is the sign of advanced disease.

-        Extrathoracic or metastatic – depending on the site of metastases. Neurological and psychiatric signs. Bone pain and pathologic fracture. Anemia due to bone marrow infiltration. Icterus in liver metastases.

-        Paraneoplastic – tumor cell may produce various hormones causing wide range of symptoms and signs. Hypercalcemia and hypophosphatemia (parathormone), hyponatremia (vasopressin), Cushing syndrome and hypokalemia (ACTH). Skin changes, neuropathy, myasthenia, migrating thrombophlebitis, finger clubbing.

Therapy

Oncological boards work as multi-disciplinary bodies at oncological centers and designate individualized treatment plans based on patients’ age, performance status, medical conditions and disease staging. Small lung cell cancer, metastatic in most cases at the time of diagnosis, rarely benefits from surgical intervention and chemotherapy is the mainstay of treatment. Early stages of non-small cell lung cancer are considered for radical surgery, with or without subsequent (adjuvant) chemotherapy. Boarder line stages may undergo neoadjuvant oncological therapy, restaging and possibly surgery with adjuvant treatment. Advanced stages are treated with chemo and radiotherapy only. Specific gene mutations like EGFR, ALK, ROS or PDL-1, if proven by specialized assays, may well be targeted with biologic therapy in palliative intent.