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We previously demonstrated that Iymphoscintigraphy could be used to study pulmonary lymphatic flow. RadiocoUoids, high-molecular-weight proteins tagged with radioactive markers, are injected percutaneously in the periphery of the lung. These molecules enter the lymph, are transported via lymphatic channels, and concentrate in the tributary hilar and mediastinal lymph nodes, where they can be visualized by nuclear scan. The goal of this study was to determine whether pulmonary Iymphoscintigraphy could be used to detect aUograft rejection after lung transplantation. Thirteen mongrel dogs underwent left lung aUotransplantation. Cyclosporine 15 mg/kg per day and azathioprine 1 mg/kg per day were given oraUy for postoperative immunosuppression. Lymphoscintigraphic studies were obtained 1 week after the operation and then at weekly intervals. In five dogs (group A), immunosuppression was continued until the animal died or was put to death 6 weeks later. Lymphoscintigraphy demonstrated reestablishment of lymphatic drainage between the lung graft and the mediastinum' in all the animals 2 to 4 weeks after transplantation. In eight dogs (group B), immunosuppression was discontinued after reestablishment of graft lymphatic drainage was documented by two consecutive Iymphoscintigraphic studies. The dogs continued to be studied with weekly scans. In group B, lymphatic drainage from the lung graft to the mediastinum disappeared 1 to 4 weeks after immunosuppression was stopped. Rejection was diagnosed clinicaUy and confirmed histologicaUy with open lung biopsies and/or autopsies in all animals. This study shows that canine aUograft lung rejection is. associated with disappearance of lymphatic drainage from lung graft to mediastinum, which can be documented by pulmonary Iymphoscintigraphy, a minimally invasive technique that can be easily repeated. Pulmonary Iymphoscintigraphy may be useful for early detection of lung allograft rejection.

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