Whenhealingoccurs,theliningepitheliummayregeneratecompletely;however,theinjuryusuallycannotberepairedandabnormaldilationandscarringpersist.Fibrosisofthebronchialandbronchiolarwallsandperibronchiolarfibrosisdevelopinmorechroniccases.Insomeinstancesthenecrosisdestroysthebronchialorbronchiolarwalls,producinganabscesscavity.
Bronchiectasis is characterized by severe, persistent cough associated with expectoration of mucopurulent, sometimes fetid, sputum. Other common symptoms
Fig. 13.12 Bronchiectasisinapatientwithcysticfibrosiswhounderwentlungresectionfortransplantation.Cutsurfaceoflungshowsmarkedlydilatedbronchifilledwithpurulentmucusthatextendtosubpleuralregions.
include dyspnea, rhinosinusitis, and hemoptysis. Symptoms often are episodic and are precipitated by upper-respiratory tract infections or the introduction of new pathogenic agents. Severe, widespread bronchiectasis may lead to significant obstructive ventilatory defects, with hypoxemia, hypercapnia, pulmonary hypertension, and cor pulmonale. However, with current treatment outcomes have improved and severe complications of bronchiectasis, such as brain abscess, amyloidosis (Chapter 5), and cor pulmonale, occur less frequently now than in the past.
CHRONICINTERSTITIAL(RESTRICTIVE,INFILTRATIVE)LUNGDISEASES
Chronic interstitial diseases are a heterogeneous group of disorders characterized by bilateral, often patchy, pulmonary fibrosis mainly affecting the walls of the alveoli (see
Fig. 13.1 ). Many of the entities in this group are of unknown cause and pathogenesis; some have an intraalveolar and an interstitial component. Chronic interstitial lung diseases are categorized based on clinicopathologic features and characteristic histology (
Table 13.2 ). However, it must be acknowledged that there is frequent overlap in histologic features among the different conditions. The shared histologic features and the similarity in clinical signs, symptoms, radiographic alterations, and pathophysiologic changes justify their consideration as a http://ebooksmedicine.net
Table 13.2 Major Categories of Chronic Interstitial Lung Disease
Usualinterstitialpneumonia(idiopathicpulmonaryfibrosis)NonspecificinterstitialpneumoniaCryptogenicorganizingpneumoniaCollagenvasculardisease-associatedPneumoconiosisTherapy-associated(drugs,radiation) group. The hallmark of these disorders is reduced compliance (stiff lungs), which in turn necessitates increased effort to breathe (dyspnea). Furthermore, damage to the alveolar epithelium and interstitial vasculature produces abnormalities in the ventilation–perfusion ratio, leading to hypoxia. Chest radiographs show small nodules, irregular lines, or “ground-glass shadows.” With progression, patients may develop respiratory failure, pulmonary hypertension, and cor pulmonale (Chapter 11). When advanced, the etiology of the underlying diseases may be difficult to determine because they all result in diffuse scarring and gross destruction of the lung, referred to as end-stage or “honeycomb” lung.