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Clinical case: Incidental pneumonectomy
This article is an eye opener about the importance of proper preoperative preparation and meticulous analysis of a patient's anatomy. During a surgical intervention for lung cancer, the surgeons mistakingly resected the common trunk of the pulmonary vein in a patient that showed a degree of anatomical variability. Keep reading and see what happened in the end and what was the reason for this mistake.
| Hilum of the lung |
It contains the following structures: primary bronchus, pulmonary artery and veins, bronchial arteries and veins, tracheobronchial lymph nodes, lymph vessels, and autonomic nerves. |
| Link between smoking and lung cancer | The risk for lung cancer never goes away even after smoking cessation. Carcinogens in cigarette smoking cause permanent DNA mutations in epithelial cells, making them more susceptible to oncogenic transformation. Exposure to other environmental carcinogens even in the absence of smoking can now induce cancer in later years. |
| Lymphatics of the lungs | The lymphatics of the lungs drain into the bronchopulmonary lymph nodes, which in turn drain into the tracheobronchial nodes. Lymph finally passes into the bronchomediastinal trunk. |
| Lung cancer staging | Criteria includes tumour size, lymph node involvement, and the presence/absence of distal metastases (TNM classification). |
After reviewing this case you should be able to describe the following:
- The structures and anatomical relationships normally found at the hilum of the lung.
- Why this patient likely had continued smoking cigarettes. Also, why even if he had stopped smoking many years ago, his cancer still likely was a result of that smoking.
- The lymph drainage and nodes of the lungs.
- How sequential axial CT scans could have failed to show the common trunk of the superior and inferior pulmonary veins.
- What is unique about this report in terms of the scientific literature?
This article is based on a case report published in the Journal "Case Reports in Surgery" in 2015, by Caroline C. Jadlowiec, Beata E. Lobel, Namita Akolkar, Michael D. Bourque, Thomas J. Devers, and David W. McFadden.
Case description
History and investigations
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The patient is a 73-year-old male with suspected left lung cancer, which was characterized as stage Ia. A CT scan of the chest showed a rounded opacity (lesion) in the left upper lobe (Figure 2). Eight years ago, the patient had coronary atherectomy resulting from an old myocardial infarction with hyperlipidemia and hypertension.
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Management
A left upper lung lobectomy was now scheduled by open thoracotomy to remove the tumor. After the thoracotomy at the fifth intercostal space, the surgeons noted that the pleurae was adherent to the thoracic wall (Figure 3).
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The surgeons did not peel off the whole lesion from the lower lobe because of potential bleeding and air leaks resulting from possible injuries of the lower lobe, and therefore were unable to identify the exact location of the inferior pulmonary vein (IPV). The superior pulmonary vein (SPV) was exposed at its normal location (Figure 4).
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The interlobular arterial vessels were hidden within a moderate fibrotic adhesion. After division of the lung parenchyma and incomplete fissures, the interlobular pulmonary arterial branches were cut after ligation with sutures. The SPV was also sutured closed and then transected. As the upper bronchial veins were exposed, the surgeons found the that the IPV was not at its expected normal location. They then explored the intralobular peripheral venous tree of the resected SPV and found a small IPV that aberrantly formed a common trunk with the SPV (Figures 4&5).
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The small IPV combined with the SPV in such a manner that the combined trunk could not be recognized as such intraoperatively. The surgeons thus then realized that they had inadvertently resected the common trunk of the SPV and IPV, mistaking the trunk for the SPV only.
Although the surgeons considered reconstructing the resected common trunk and IPV, this course was rejected in order to prevent possible postoperative complications such as pulmonary venous occlusion, congestion due to thrombus, and pulmonary edema due to the anastomotic stenosis. The surgeons decided to now perform a complete pneumonectomy with dissection of the mediastinal lymph nodes.
While the surgery was in progress, the surgeons explained to the patient’s family the unexpected adverse event and the conversion of the scheduled operation to a complete pneumonectomy. The surgeons obtained informed consent from the patient’s family. After the pneumonectomy, the patient’s postoperative recovery was good.
Evolution
The postoperative pathology revealed the tumor to be an adenocarcinoma. During the 5.5-year follow-up, the patient remained healthy with good quality of life. Metastases did not develop and neither did local recurrences. At this time the postoperative pulmonary function test showed a restrictive pattern.
Anatomical and surgical considerations
Variations in the pulmonary venous drainage pattern are well known. The variation is based on how much of the pulmonary veins are incorporated into the left atrium during development. In order to perform a successful surgery for lung cancer, a preoperative evaluation on the staging, general anesthesia tolerance and preoperative risk are very important in surgical planning. Preoperatively, in this case there was a flawed determination of the anatomical location and relationship of vessels and bronchus. Although contrast enhanced CT was performed prior to surgery, the common trunk was poorly visualized (Figure 5).
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The extirpated lung revealed that the SPV and IPV formed a common trunk inside the upper pulmonary lobe (Figure 4). During the operation the surgeons were unsure as to whether they should reconstruct the IPV or perform a complete pneumonectomy. They decided to perform the pneumonectomy in order to minimize postoperative complications such as postoperative venous occlusion and congestion of the lower lobe. Retrospectively, the CT images were reexamined and they did indeed show a small IPV that joined the SPV to form a common trunk. However this connection was not visible in any single axial image (Figure 5).
Although the present case was rare and the common trunk of the pulmonary vein was unexpectedly resected, the surgeons reported that they learned a basic lesson in thoracic surgery. That is, at the preoperative phase, detailed assessment of the pulmonary vascular anatomical locations and their three-dimensional relationships are essential.
Explanations to Objectives
Objectives
- The structures and anatomical relationships normally found at the hilum of the lung.
- Why this patient likely had continued smoking cigarettes. Also, why even if he had stopped smoking many years ago, his cancer still likely was a result of that smoking.
- The lymph drainage and nodes of the lungs.
- How sequential axial CT scans could have failed to show the common trunk of the superior and inferior pulmonary veins.
- What is unique about this report in terms of the scientific literature?
Hilum of the Lung
The structures at the hilum (root) of the lung consist of the primary bronchus, the pulmonary artery and veins, the bronchial arteries and veins, tracheobronchial lymph nodes, lymph vessels and autonomic nerves, all of which are enclosed by pleura.
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An important point to note here is that it is the bronchial arteries that provide oxygenated blood to lung tissue not the pulmonary arteries. The primary structures composing the root of each lung are arranged in a similar manner anterior to posterior: the pulmonary veins are anterior, the pulmonary artery is in the middle, and the bronchus and bronchial vessels are posterior (Figures 7&8). The left hilum has a notably high pulmonary artery, which is known as the eparterial artery.
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Smoking and Lung Cancer
Tobacco products contain a natural product (nicotine) that is highly addictive. It creates a physical dependence by directly acting on receptors in the central nervous system. Therefore, it is extremely difficult to stop smoking. It requires much more than a casual will to succeed in nicotine withdrawal. However, if a smoker can stop smoking the health benefits increase over time exponentially. Five years after smoking the risk of dying from heart disease goes down significantly and after 20 years the risk of dying from heart disease becomes equal to lifetime nonsmokers.
Unfortunately, the level of benefit from smoking cessation is not equally significant for lung cancer. The risk of dying from lung cancer goes down by 21% after five years but the risk never goes down to nonsmoker level even after decades. Lung cancer develops over a prolonged period and requires multiple molecular steps. Carcinogens in cigarette smoking cause permanent genetic damages in the form of DNA mutations in epithelial cells, which become more susceptible to oncogenic transformation. Exposure to other environmental carcinogens even in the absence of smoking can now induce cancer in later years. In some cases, it may take 5-10 years for a single cancer cell to grow to a clinically detectable tumor mass.
Lymphatics of the Lungs
The lymphatics of the lungs and visceral pleura drain into the bronchopulmonary lymph nodes, which are located at the branching points of the larger bronchi. Lymph from these nodes passes to the tracheobronchial nodes located within the hila of the lungs. From these nodes the lymph passes into the bronchomediastinal trunk on each side.
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Staging of lung cancer is typically based on three parameters; size and extent of the primary tumor, involvement of local lymph nodes and presence of distant metastasis. The patient in this case had a Stage 1A tumor, which indicates a very early stage with the primary tumor being less than 2 cm in size and not involving the visceral pleura or lobar bronchus, in addition to lack of distant metastasis and lack of any lymph node involvement.
Variability of the Common Trunk of the Pulmonary Veins
In CT, scanning decisions have to made as to how many axial “slices” are viewed for a given body region and how “thick” the slices should be. It is possible for a radiologist to view very thin (1mm) axial slices through, for example, a patient’s thorax and to view every single slice. Based on the individual patient, the diagnosis, and the area being scanned, the radiologist decides the distance between viewed axial slices and also the thickness of each slice (1-10 mm). Because each dot (pixel) viewed on a scan represents the average density values of the structures at that spot for that thickness, is a tradeoff that has to be made. The thicker the slice the more likely a very small lesion will get masked (volume weighted average). On the other hand, although slices that are very thin are more likely than thick sections to show a small lesion, the cost of viewing hundreds of sections is prohibitive.
The risk of too few sections is clearly shown by this case in which the combining of the superior and inferior pulmonary veins was not evident in any of the single scans done preoperatively. Had the surgeons seen thinner and/or closer sections, this connection might have been seen. Similarly, had the surgeons viewed some coronal as well as axial sections, the connection might have been seen.
Importance of Publishing Medical Errors
The authors of this book applaud the surgeons in this case for, in essence, publishing a record of a mistake they made in the hopes that such a mistake will not be repeated. We would hope that others would publish similarly significant surgical errors so that other physicians might avoid errors that can cause unnecessary morbidity and mortality.
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