Incidence and Impact of RAS-Like Opacities During Preserved Lung Function After Lung Transplantation

Chronic lung allograft dysfunction (CLAD) limits survival after lung transplantation. Restrictive allograft syndrome (RAS) is the most aggressive subtype of CLAD, and its diagnosis requires permanent lung function decline, restrictive lung physiology, and RAS-like opacities (RLOs) on lung imaging. We aimed to investigate the incidence of RLOs in patients with preserved lung function, and to determine whether RLOs later progressed into RAS-type CLAD or were associated with adverse clinical outcome.

We retrospectively reviewed the presence of RLOs during stable and preserved lung function (FEV1> 80% of baseline) from serial CT scans of 167 consecutive adult lung transplant patients. RLOs were evaluated from serial CT scans for their distribution, radiological morphology, and extent. The impact of RLOs on lung function, CT-volumetry, and patient outcome was determined.

Eleven patients (7%) with preserved lung function developed RLOs at a median of 3.0 years after transplantation. The RLOs localized predominantly in the upper lobes, consisted of ground glass, nodular, and reticular opacities, and consolidations, and progressed over time leading to extensive pattern of RLOs in 45% of the 11 patients. Eight patients (74%) with RLOs later developed CLAD at a median of 2.8 years after occurrence of RLOs. Their CLAD phenotype was RAS in only two patients and Mixed in five patients (63%). The occurrence of RLOs during preserved lung function was not associated with reduced long-term survival.

The presence of progressing RLOs detected in lung transplant recipients with preserved lung function was not associated with reduced survival during follow-up. The majority of patients with RLOs developed CLAD which was mostly of mixed phenotype.