Mechanisms and features of pleural pain
Pain syndrome in respiratory system pathologies is almost always associated with the involvement of the pleural membranes. The lung parenchyma itself and the bronchial tree are extremely poor in nociceptors, which is why inflammation, stretching, or irritation specifically of the parietal and visceral pleura triggers a pronounced pain reaction.
Classical pleural pain is characterized by the following features:
- Sharpness: sensations are often stabbing, sharp, and sometimes "dagger-like" in nature.
- Respiratory dependence: discomfort has a clear connection with the act of breathing. Pain sharply increases at the peak of a deep breath, as well as during coughing or sneezing.
- Effect of body position: the pain increases when the patient leans the trunk toward the healthy side, as this causes greater tension of the inflamed pleura. Conversely, the condition subjectively improves with fixation (immobilization) of the chest or when lying on the affected side, as this limits lung excursion.
The main cause of such sensations is the friction of inflamed membranes against each other. An interesting dynamic is observed in exudative processes: if fluid begins to accumulate in the cavity (transudate or exudate), the membranes separate, friction stops, and the pain syndrome paradoxically subsides.
Pulmonary causes of thorbalgia
Most often, thorbalgia of respiratory origin develops against the background of dry (fibrinous) pleurisy. In exudative pleurisy, discomfort is registered exclusively in the initial stages before the effusion has had time to accumulate.
The pleura is frequently involved secondarily when the pathological focus is located in the subpleural zones of the lung tissue. Such secondary causes include:
- Lobar pneumonia: the appearance of pain here serves as a reliable clinical marker that inflammatory infiltration has reached the periphery of the lung.
- Pulmonary infarction.
- Tumor neoplasms located subpleurally.
In rare cases, discomfort is caused by adhesions resulting from past pleurisy. It is also worth noting that in pericarditis, pain syndrome occurs due to the spread of inflammation from the pericardial sac directly to the adjacent visceral pleura.
Diaphragmatic pleurisy and spontaneous pneumothorax
Inflammation of the diaphragmatic pleura is distinguished separately. Due to the specific innervation of the diaphragm, pain can radiate to the neck and shoulder on the affected side. In addition, the pain impulse may spread into the abdominal cavity, developing a picture that completely mimics an "acute abdomen" (due to irritation of the diaphragmatic part of the peritoneum).
Special attention is required for spontaneous pneumothorax. This urgent condition causes severe pleural irritation and is characterized by a classical triad of signs:
- Acute pain syndrome triggered by the rupture of the visceral membrane.
- Pronounced respiratory disorders in the form of dyspnea caused by compression atelectasis (acute lung collapse under air pressure).
- Hemodynamic shifts—collapse and drop in blood pressure due to mediastinal shift.
Important: If pneumothorax is accompanied by the penetration of air into the mediastinum (mediastinal emphysema), the nature of the pain can mimic myocardial infarction.
Differential diagnosis with extrapulmonary processes
To avoid diagnostic errors, pleural pain must be distinguished from pathologies of adjacent structures:
- Mediastinal organs: Tumors and mediastinitis produce widespread, pressing, and squeezing pain behind the sternum that closely resembles an angina attack.
- Respiratory tract: In tracheitis, discomfort is localized behind the upper sternum and clearly intensifies with coughing.
- Musculoskeletal system: Damage to musculoskeletal and neural structures includes intercostal neuralgia (characterized by sharp tenderness upon palpation of nerve exit points near the spine and the edge of the sternum), myositis (muscle inflammation), chondritis (inflammation of the costal cartilages in the area of attachment to the sternum), as well as costal periostitis (damage to the periosteum) and rib fractures.
- Digestive organs: Pain can radiate to the chest in acute cholecystitis, acute appendicitis, splenic infarction, or liver abscess formation.
Briefly: answers to topical questions
What cardiovascular diseases are frequent causes of thorbalgia?
Cardiovascular causes of chest pain directly indicated in the sources include:
- Angina pectoris (CHD) — in the presence of chest pain, it must be ruled out first.
- Myocardial infarction — belongs to the high-risk group of conditions characterized by intense, prolonged, paroxysmal pain behind the sternum or on the left, and a drop in blood pressure.
- Pulmonary embolism (PE) — also belongs to high-risk conditions with such a clinical presentation.
- Aortic dissection — belongs to the high-risk group of conditions; also indicated among associated vascular pathologies.
What radiographic signs are characteristic of spontaneous pneumothorax?
Classically, a chest X-ray in pneumothorax shows the contour of a slightly collapsed lung and a very thin line of the visceral pleura. When the patient is lying supine, specific atypical radiological signs form:
- Ipsilateral increase in radiolucency — can be generalized or detected in the hypochondrium.
- Deep sulcus sign (deep sulcus sign) — a deep, finger-like lateral costodiaphragmatic recess.
- Double diaphragm sign (double diaphragm sign) — a visible anterior costodiaphragmatic recess that can mimic the adjacent diaphragm.
- Lucency stripe — runs parallel to the diaphragm and/or mediastinum with an excessively sharp border of the latter.
The posture rule in pleurisy: "The diseased pleura loves rest — lie on the affected side, do not lean toward the healthy side."
Class and exam questions
Why does chest pain disappear over time in exudative pleurisy?
As pathological fluid (effusion) accumulates in the cavity, the visceral and parietal pleural membranes move apart. Friction of the inflamed surfaces against each other ceases, leading to the abatement of the pain syndrome.
How to quickly distinguish intercostal neuralgia from pleurisy?
In neuralgia, pain sharply increases upon palpation along the intercostal spaces, especially at the points of nerve trunk exit (near the spine and along the edges of the sternum).
In what case can spontaneous pneumothorax mimic myocardial infarction?
This picture is observed with concomitant mediastinal emphysema, when air penetrates the mediastinal tissue, causing a pronounced squeezing pain syndrome.
What else to study on this topic
- Pathogenesis and differential diagnosis of compression atelectasis.
- Features of percussion and auscultation findings in the presence of fluid in the pleural cavity.
- Mechanisms of transudate and exudate formation in pleurisy.
- Topographic anatomy and innervation of the diaphragmatic pleura.
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