MANAGEMENT OF THE POSTRESECTION SPACE IN TUBERCULOSIS

The “Balloon-Like” Sign: Differential Diagnosis between Postoperative Air Leak and Residual Pleural Space: Radiological Findings and Clinical Implications of the Young–Laplace Equation

Simple Summary

Postoperative residual pleural space and postoperative air leaks after lung resection are two different clinical entities requiring completely different approaches. Residual postoperative pleural space is a part of the pleural cavity that is not fully reoccupied by the remaining lung after pulmonary resection. No treatment is needed in the asymptomatic residual pleural space without any persistent air leak, and chest drain removal can be safely planned. On the contrary, an active and prolonged air leak after lung resection is an absolute contraindication to chest drain removal that may culminate in hypertensive pneumothorax, subcutaneous emphysema, and severe respiratory symptoms. In order to further contribute to an appropriate differential diagnosis between these two settings, we propose a radiological sign that is observed only in the case of residual plural space. In this case, in fact, the lung takes the form of a round balloon due to the hyperinflation condition, which is governed by the Young–Laplace equation describing the capillary pressure difference sustained across the interface between two static fluids, such as water and air, due to the phenomenon of wall tension.

Abstract

In this paper, we propose a radiological sign for an appropriate differential diagnosis between postoperative pleural space and active air leak after lung resection. In the case of residual pleural space without any active air leak, the lung takes the form of a round balloon due to the hyperinflation condition, which is governed by the Young–Laplace equation describing the capillary pressure difference sustained across the interface between two static fluids, such as water and air, due to the phenomenon of wall tension. The two principal mechanisms by which a lung forms a spherical image are shear-controlled detachment induced by shear stress on the membrane surface, and spontaneous detachment induced by a gradient in Young–Laplace pressure. On the contrary, the lung maintains its tapered shape in the case of an active air leak because the continuous air refill does not allow a complete parenchyma re-expansion.

Postoperative residual pleural spaces: characteristics and natural history

This study was conducted in order to re-define the incidence and natural history of postresectional residual pleural spaces (PRS). From 1997 to 2005, 966 patients who were subjected to less than entire lung resections, were followed and any cases of PRS were recorded. The records of these patients were retrospectively analyzed for age, gender, type of resection, side, apical or basal location, size, PRS wall thickness, empyema as well as for bronchopleural fistula occurence, management, and outcome. Postresectional residual pleural spaces outcome was correlated with space characteristics. A total of 92 cases (9.5%) of PRS were documented which developed frequently ( p < 0.001) after upper lobectomies, malignant disease, at an apical location, and on the right side. Unfavorable outcome was strongly correlated with age > 70 years ( p < 0.001), air leak ( p < 0.001), empyema ( p < 0.001), and thickened pleura ( p < 0.001). Good prognosis of PRS was strongly correlated with male gender, apical location, right side, normal pleura thickness, and small size. Postresectional residual pleural spaces of small size without any associated complications should not prolong hospitalization time.