Pleural effusion, pneumothorax, hemothorax and atelectasis: Pathology review

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Case Study0:00–1:30

During a night shift in the emergency department. You see George, a 21 year old who complains of sharp stabbing, left sided chest pain and shortness of breath, both of which appeared suddenly while he was playing video games.
He is a smoker and mentions his younger brother suffered a pneumothorax last year. On examination, the left side of his chest is slightly more expanded than the right side and his breathing is very shallow.
The affected side is also hyper resonant on percussion and there's diminished breath sounds on auscultation. Then there's Anna a 58 year old with progressively worsening dyspnea, pleuritic chest pain and fever.
She has a history of diabetes and cirrhosis. On examination, her BP and heart rate are both increased and jugular venous pressure is elevated.
Also the base of her left lung field is dull to percussion with decreased breath sounds, her lower extremities have pitting edema up to the knee.
X-rays were performed in both individuals. In George's case, it showed a retracted visceral pleural edge with a decrease in the left lung volume.
In Anna, it showed left-sided costophrenic angle blurring. Now, they both seem to present with conditions affecting the pleura.

Physiology1:30–3:09

But to understand the pathophysiology, it's a good idea to review the anatomy and physiology first. Ok.
So the pleura covers the lungs and consists of the parietal pleura which is stuck to the chest wall and the visceral pleura which is stuck to the lungs.
It extends all the way up to the clavicle and first rib, which is something that will help you understand why neck injuries can cause tension.
Pneumothorax also know the inferior limit of the pleura is the seventh rib on the midclavicular line, the 10th rib on the mid axillary line and the 12th rib on the paravertebral line between the layers of the pleura is the pleural space containing 10 to 20 mL of a lubricating fluid that helps reduce friction as the lungs expand and contract.
There's also pressure within the pleural space established by two main opposing forces. One is the muscle tension of the diaphragm and chest wall which contract and expand the thoracic cavity outwards.
The other is the elastic recoil of the lungs, which is the lungs tendency to collapse inward. The two forces pulling in opposite directions creates a slight vacuum in the pleural space with the pressure of negative five centimeters of water relative to zero centimeters of water in both the thoracic cavity and the lungs.
The difference in pressure aids, air exchange during inspiration and expiration to help the lungs keep their shape and not collapse.
Ok. Now, let's look at the disorders that affect the pleura starting with pneumothorax.

Pneumothorax3:09–9:45

A pneumothorax forms when the seal of the pleural space is punctured, letting air in and equalizing the pressure within the pleural space.
Lung and chest cavity. As a result, the negative pleural pressure is lost and the equilibrium between the two opposing forces disappears.
The result is the affected lung simply pulls inwards and collapses. Now, there are many types of pneumothorax.
A primary spontaneous pneumothorax is one that develops in the absence of an underlying condition. And the clue to help you out is that these individuals tend to be thin, tall young males who smoke.
Another high yield fact is that they often have a family history of pneumothorax. The cause is unknown but they are believed to be due to apical subpleural blebs that rupture without warning.
A secondary spontaneous pneumothorax is one that develops in someone with an underlying lung disease where the lung or pleura structure is altered.
One example you might encounter is emphysema where bully which are air pockets form on the surface of the lungs and then rupture.
This creates a large hole in the visceral pleura and air can go from the airway directly into the pleural space. There is also a traumatic pneumothorax which is when trauma like a gunshot or stab wound or sometimes even iatrogenic causes like lung biopsy or barotrauma due to mechanical ventilation, rips through the parietal pleura, allowing air to enter into the pleural space finally, there's tension pneumothorax, which can develop similarly to a spontaneous pneumothorax.
One difference to keep in mind is that a flap of tissue near the leak can create a one way valve for air to flow into the pleural space.
In other words, air can enter but cannot leave. So air accumulates in the chest cavity and it pushes the organs in the mediastinum away from the affected side, which is called a mediastinal shift.
This also causes compression of the organs, especially the venous system. This prevents blood from returning to the heart which will reduce cardiac output and ultimately lead to obstructive shock.
The symptoms of a spontaneous pneumothorax might only consist of shortness of breath and sudden unilateral pleuritic chest pain.
This is a sharp knife like pain that worsens with deep inspiration, coughing, sneezing or laughing due to irritation of the parietal pleura by the expanding lung.
Clinical examination begins with vitals which are usually normal except for rapid breathing or tachypnea. Now, on inspection, because the chest wall springs outward a bit as the lung collapses, the chest wall on the affected side might appear bigger than the normal side.
On chest palpation, chest expansion is uneven due to decreased chest wall movement of the affected side and tactile fremitus is decreased.
Tactile fremitus can be felt when the hand is placed on the chest wall. When a person says 99 the chest wall vibrates.
If there's excess air in the pleural space it absorbs some of this vibration energy. Thus, the vibrations weaken.
Now when the chest is percussed, the extra air in the pleural space makes the resonance sound get louder. And this is something that can help you differentiate it from a hemothorax where the chest percussion is usually dull.
Also the extra air in the pleural space changes sound transmission in the chest. So on auscultation, normal breath sounds are diminished.
Now in attention pneumothorax, because air builds up, increasing the pressure inside the chest, the air starts compressing the organs in there.
It's important to know that if it compresses the heart, it can lead to decreased cardiac output, low arterial BP, distended, neck veins and tachycardia.
Moreover compression of the inferior vena cava decreases venous return which leads to edema and even cardiac arrest. There is also deviation of the trachea towards the unaffected side.
Finally, the normal lung can also be compressed, further limiting air exchange resulting in cyanosis and respiratory failure.
Typically an X ray or CT is needed for diagnosis where you should look for a retracted visceral pleural edge, usually seen as a very thin sharp white line alongside a decreased lung volume due to the lung, collapsing the space beyond the visceral line is mostly black because the space where the lung should be is filled with air.
Commonly in attention pneumothorax, an X ray or CT might show a mediastinal shift which is seen as a tracheal deviation and displacement of chest structures away from the affected side.
Now, treatment is not usually required in spontaneous pneumothorax as they are usually small and the pleura will heal over time in a larger pneumothorax that's causing severe symptoms.
The air needs to be removed with a syringe or a chest tube connected to a one wave valve system. In a tension pneumothorax, the air needs to be removed right away.
Sometimes even before the diagnosis is confirmed by imaging. Remember that this is usually done by inserting a needle or a chest tube in the space between the 2nd and 3rd rib of the affected side on the midclavicular line which decompresses the chest and provides an escape route for the trapped air.
Next, we have pleural effusion which is excess fluid in the pleural space. This can happen due to either a transudative exudative or lymphatic effusion.

Pleural Effusion9:45–14:40

Ok. So a transudative pleural effusion is when the liquid inside the pleural space is a transudate.
It occurs when too much fluid starts to leave the capillaries either because of increased hydrostatic pressure or decreased oncotic pressure in the blood vessels.
Usually in the context of conditions like heart failure, cirrhosis and nephrotic syndrome, you'll be able to differentiate it by the fact that a transudate is low in protein.
This can be due to decreased protein production caused by cirrhosis or because the proteins are lost in urine. Like when there's nephrotic syndrome, transudate also has a low lactate dehydrogenase content which is a substance released whenever there's tissue damage and it appears clear most of the time next.
In exudative pleural effusion. The fluid is an exudate which is caused by inflammation of the pulmonary capillaries.
This allows fluid immune cells and large proteins like lactate dehydrogenase to leak out of the capillaries and into the pleural space.
In questions, it might appear as a cloudy liquid rich in protein and lactate dehydrogenase. So remember that exudate is associated with lung damage.
The causes vary from trauma, malignancy, inflammatory conditions like lupus or an infection like pneumonia. A rare type of exudative pleural effusion is caused by mesothelioma and it's called a hemorrhagic pleural effusion.
Another rare type of pleural effusion is found in Meigs syndrome, which is a triad of ovarian fibroma ascites and pleural effusion.
However, its origin is unknown with some classifying it as a transudate. Whereas others stating it as an exudate.
Finally, lymphatic pleural effusion called a chylothorax is when the thoracic duct is obstructed by tumors or surgery. And lymphatic fluid accumulates in the pleural space.
You'll recognize the lymphatic fluid by its milky color and high triglyceride content. Now, the symptoms of pleural effusion depends on its size.
A small effusion might go unnoticed whereas a large one might cause pleuritic chest pain. Another giveaway is that the pain can radiate to the neck and shoulder through the phrenic nerve and this is called referred pain.
Individuals also develop shortness of breath, especially when lying down flat. Classically on examination, a pleural effusion will cause local signs such as unilateral decreased chest expansion and decreased tactile fremitus on palpation as well as dullness to percussion, which will help you differentiate it from pneumothorax along with decreased breath, sounds on auscultation.
All of these signs are on the affected side and due to excess fluid in the pleural space. Finally, a large pleural effusion can start to compress the chest organs in the same way as a pneumothorax, which leads to a similar clinical picture, like low BP, distended, neck veins, tachycardia and lower extremity edema diagnosis can be made by x-ray in someone standing upright because the pleural effusion fluid can settle into the costophrenic angle, which is where the diaphragm meets the chest wall.
It causes a blurring of the angle as fluid displaces the air that's usually there on an X ray taken of someone lying down gravity will cause the pleural effusion to settle along the chest wall creating a layering effect.
Now, it's important to note that in a large or suspicious pleural effusion. The next step would be a diagnostic thoracentesis which is inserting a hollow needle over the top of a rib to avoid injuring the neurovascular bundle running along the underside of each rib in order to obtain a sample of the effusion.
The sample is then analyzed to determine its composition. Next treatment in larger effusions consists of removing the pleural effusion fluid by therapeutic thoracentesis, both to relieve symptoms and find out the cause.
Additional management might be needed to address the underlying cause of the effusion. Ok.
So third is hemothorax, which is blood in the pleural space. The condition is usually a consequence of blunt or penetrating trauma to the lungs and the source of blood may be the chest wall and pleura lung, parenchyma, heart or great vessels.

Hemothorax14:40–16:47

It could also be iatrogenically induced like for example, by anticoagulant drugs or by intubation. Usually, what happens is that something causes the pleuric to rupture, which means blood will accumulate in the pleural space as it has no way of being drained.
Sometimes the bleeding can be so severe that more than a liter of blood accumulates inside the chest cavity, which constitutes a massive hemothorax or it can be accompanied by pneumothorax leading to what is called a hemopneumothorax.
Ok. So a small hemothorax usually causes little in terms of symptoms.
In a larger one. There might be dyspnea mostly because the lungs cant expand properly.
A large hemothorax could also present with signs of blood loss, like clammy, skin, rapid heart rate and low BP, just like with pleural effusion.
They can have uneven chest wall expansion, decreased tactile fremitus, dullness to percussion and decreased breath sounds on auscultation diagnosis begins with chest X ray showing findings similar to those of pleural effusion.
This is why a diagnostic thoracentesis is needed to confirm the presence of blood in the pleural fluid tube, thoracostomy drainage is the primary mode of treatment for larger collections of blood.
A technique similar to a pneumothorax, evacuation, smaller ones generally require no treatment. Blood usually reabsorbs throughout the course of several weeks.

Atelectasis16:47–21:11

Ok. The last disorder is atelectasis.
Although it doesn't directly affect the pleura like the other disorders we've discussed. Those disorders can cause atelectasis.
In addition, a lot of the symptoms and physical exam findings are similar. So we will go over it in this video.
Now, atelectasis is the loss of lung volume secondary to alveolar collapse. It may include a lung subsegment or the entire lung.
But unlike pneumothorax, which also cause the lung to collapse. Atelectasis is not caused by the leakage of air into the pleural space.
Instead, there are many things that can cause atelectasis. Obstructive atelectasis is the most common and results from obstruction of the bronchi between the alveoli and the trachea.
This prevents gas from moving into the alveoli. So they collapse causes of obstructive atelectasis include foreign objects, tumors and mucous plugs, compressive atelectasis is when there's something pressing on the lungs which decreases their volume.
Some causes can include large pleural effusions, hemothorax and tension, pneumothorax, contraction, atelectasis is due to scarring of lung, parenchyma that distorts the alveoli and impairs elastic recoil, making it impossible for the lungs to fully expand.
This is commonly seen in sarcoidosis and finally adhesive atelectasis is due to the lack of surfactant which reduces surface tension at the alveolar air interface and prevents the walls of the alveoli from sticking to each other.
Now, you might encounter this in questions related to neonatal respiratory distress syndrome. A condition where a newborn's type two pneumocytes are not matured enough to secrete surfactant, adhesive atelectasis can also be associated with lamellar body dysfunction, which are secretory organelles that secrete phospholipids.
The main components of surfactant. Now, atelectasis may also develop in individuals undergoing general anesthesia and persist for several weeks.
Depression of the respiratory center and decreased activity and coordination of the diaphragm and other respiratory muscles lead to hypoventilation of the dependent parts of the lungs causing atelectasis.
Ok. So the symptoms secondary to this reduction in the lung surface area and impaired gas exchange might include dyspnea, cough and chest pain.
Vitals might show tachypnea and tachycardia. Physical exam findings can be similar to pleural effusion on the affected side.
There's decreased chest wall expansion, decreased tactile fremitus, dullness to percussion and decreased breath sounds, but crackles can sometimes be heard.
Diagnosis is based on chest X ray or CT scans demonstrating direct and indirect signs of lobar collapse, direct signs include displacement of the lungs, fissures and opacification of the collapsed lobe.
Indirect signs include displacement of the hilum, mediastinal shift toward the site of collapse, loss of volume of the affected hemithorax, elevation of the diaphragm on the same side, crowding of the ribs and compensatory hyperlucency of the remaining lobes, meaning the unaffected lobes will look more black.
Treatment depends heavily on the underlying cause. It can include physiotherapy, focusing on deep breathing and encouraging coughing, mechanical ventilation, like continuous positive airway pressure, which delivers pressurized air or oxygen through a nose or face mask to help ensure that the alveoli do not collapse.
All right, as a quick recap, pneumothorax is when there's air in the pleural space resulting in loss of negative pressure.

Review21:11–23:52

There are many types. The most serious being tension, pneumothorax, which is when there's a flap of tissue, creating a one way valve that traps the air inside the pleural space.
Symptoms consist of shortness of breath and pleuritic chest pain. And clinical examination can include decreased tactile fremitus, decreased breath, sounds uneven chest wall expansion and hyper resonance on percussion.
Pleural effusion is when excess fluid collects in the pleural space. And it can be due to transudative and exudative causes or due to blockage of lymphatic drainage.
Symptoms can include pleuritic chest pain and shortness of breath. While clinical examination may reveal decreased tactile fremitus, decreased breath, sounds unilateral, decreased chest expansion and dullness to percussion.
Hemothorax is blood in the pleural space. The condition is usually a consequence of blunt or penetrating trauma to the lungs which causes the pleura to rupture and blood to accumulate into the pleural space.
Individuals may develop the same symptoms and findings as pleural effusion. But if there's massive blood loss, they might also have clammy skin rapid heart rate, low BP and finally atelectasis is the loss of lung volume, secondary to alveolar collapse.
There are several types of atelectasis usually differentiated by their cause signs and symptoms are similar to pleural effusion.
But crackles can often be heard on auscultation. Diagnosis of pneumothorax is based on chest X ray and treatment consists of chest needle decompression, diagnosis of pleural effusion begins with chest X ray and continues with thoracentesis which can also be used as a treatment method.
Diagnosis of hemothorax begins with chest x rays showing findings similar to those of pleural effusion and is confirmed by thoracentesis.
Treatment consists of tube thoracostomy drainage. Finally, diagnosis of atelectasis is based on direct and indirect signs on chest X ray or CT scans and treatment focuses on treating the underlying cause.

Summary23:52–25:09

Now, back to our cases, George is a young smoker with the family history of pneumothorax, who comes in with left sided pleuritic chest pain and shortness of breath.
On examination. He presented with shallow breathing and a hyper expanded chest hyperresonance with diminished breath sounds these symptoms especially the hyper resonance on the affected side suggests a pneumothorax.
His X ray showed a retracted visceral pleural edge with a reduced lung volume in the lung surface and confirmed the diagnosis.
Ok. So, Anna has a history of diabetes and cirrhosis and presents with progressively worsening dyspnea and pleuritic chest pain.
On physical exam. There was elevated jugular venous pressure, the left lung field is delta percussion and absent breath sounds on the left side.
These symptoms and physical findings suggest a pleural effusion likely secondary to her cirrhosis chest xray showed costophrenic angle blurring which supports the diagnosis.
But a thoracentesis needs to be done to find out the composition of the fluid in the pleura.