Diagnosis of chronic graft failure after lung transplantation

Since 1984, when bronchiolitis obliterans (BO) was recognized as the main factor influencing long-term survival after lung and heart-lung transplantation, this condition has remained the main cause of morbidity and mortality one year after transplant. It is characterized by submucosal lymphocytic infiltration of the airways, epithelial disruption, fibromyxoid granulation and ultimately partial or complete occlusion of bronchioli. Despite attempts to refine the diagnostic process, decline in spirometry and the so-called bronchiolitis obliterans syndrome (BOS) remains the most clinically relevant surrogate marker for BO. CT remains the most useful radiographic adjunct in the diagnosis of BO but there are no pathognomonic findings and results should be interpreted within clinical context. The value of a bronchoscopic study including BAL and trans-bronchial biopsies in the diagnosis of BO is to exclude other potential causes of functional decline, rather than establishing histological diagnosis. Recurrent episodes of acute rejection are the most widely accepted risk factor for BO but even mild rejection or a single episode of rejection may be significant. Acid or non-acid reflux disease, infection especially with viruses, HLA mismatching, lymphocytic bronchitis and possibly primary graft dysfunction may also predispose to BO. Effective measures to prevent or treat BO will undoubtedly have the greatest impact on long-term survival in lung transplant recipients.