Fibrous Pleural Adhesions
Adhesions; Fibrous pleural adhesions; Pleural adhesions
Fibrous pleural adhesions are common after any surgical procedure affecting the pleural space. Adhesions form from one pleural surface across to the other pleural surface. The adhesion is generally composed of delicate strands of fibrous tissue.
Injury to the pleural surfaces induces an inflammatory reaction involving cellular elements, tissue factors, and coagulation factors. The early adhesion is made mostly of fibrin gel matrix, which is made of fibrin polymers reacting with fibronectin and amino acids. If the tissue plasminogen activator system does not remove the fibrin gel matrix and fibrinolysis does not occur, connective tissue scarring and adhesions develop from the ingrowth of fibroblasts. Fibrinolysis is impaired by, among other things, ischemia, foreign bodies, bacteria, desiccation, and thermal injury.
Fibrin is deposited at the site of injury fairly quickly after the trauma, and fibrin deposition peaks on postinjury day 4 or 5. Polymorphonuclear neutrophils, macrophages, and mesothelial cells are recruited for repair. Macrophages are the most common cell-type identified 5 days after the initial injury and are also responsible for recruiting new mesothelial cells to the injury surface. These cells form small islands across the injured area before proliferating into sheets of cells that will cover the entire surface within 7 days of the initial injury.
Ultrasound may be useful in identifying pleural adhesions prior to surgery. Imaging the lower chest is more sensitive, as there the adhesions are detected by the absence of pleural sliding during diaphragmatic movement. This technique is of limited usefulness in patients with chronic obstructive pulmonary disease because there are smaller respiratory movements.
Prevention of adhesions has proven to be challenging. Video-assisted thoracoscopic surgery has lowered the incidence of adhesion formation to the chest wall but not in the mediastinal and interlobar pleurae.
Fibrous pleural adhesions will develop in 25–35% of adult patients undergoing thoracotomy. Patients who undergo partial resection for pneumothorax develop adhesions 10% of the time. Lobectomy patients develop adhesions about 50–60% of the time.
Adhesions can also develop as a consequence of malignancy or infection, where an exudative effusion can lead to pleural thickening and eventually fibrous pleural adhesion.
Fibrous pleural adhesions can be found at any age.
Fibrous pleural adhesions have no sex predilection.
Fibrous pleural adhesions occur bilaterally and in both the upper and lower chest.
Treatment involves surgical lysis of adhesions when cases are severe.
The vast majority of adhesions are asymptomatic and do not require intervention. If surgical lysis of adhesions is required, the adhesions will often re-form. The presence of pleural adhesion is a known cause for an unresolving pneumothorax. Surgical lysis of adhesions can be particularly dangerous with severe adhesions because dense adhesions increase the risk for pulmonary hemorrhage.
Extensive adhesions can lead to narrowing of the intercostal space and thorax, adversely affecting the respiratory function of the lungs.
Grossly, fibrous bands of tissue connect visceral pleura and parietal pleura.
Within 1 week of injury, adhesions are covered by a continuous single layer of flat mesothelial cells. After 1 week, adhesions are composed of loose irregular collagenous connective tissue in various stages of maturity. The collagen fibers are arranged in discrete bundles and often aligned parallel to the longitudinal axis of the adhesion. Numerous fibroblasts are seen among bundles of collagen fibers, and a variable number of macrophages, lymphocytes, and mast cells can be seen among the fibers. At 1 month, the cellular content of the adhesion is less dense and elongated spindle-shaped fibroblasts lie between thick bundles of dense collagen fibers. Neovascularization can be seen within days of the injury on both the visceral and parietal segments of the adhesion. Enlarged, dilated blood and lymphatic vessels may be seen at the edge of the adhesion.
Fibrous pleural adhesions are destructive and typically easily diagnosed.
References and Further Reading
- Tanaka, K., Hida, Y., Kaga, K., Kato, H., Iizuka, M., et al. (2010). Video-assisted thoracoscopic surgery lowers the incidence of adhesion to the chest wall but not to the mediastinal and interlobar pleurae. Surgical Laparoscopy, Endoscopy & Percutaneous Techniques, 20(1), 46–48.CrossRefGoogle Scholar