Sequential CT in monitoring experimental lung transplant

The criteria for diagnosis of lung rejection remain controversial. In this study early changes in lung rejection were characterized using sequential CT with the aim of developing a sensitive and safe monitoring method, which would also provide specific information on graft status. Twenty-one experimental single lung transplants (SLTs) in piglets, including unmodified rejections, immunosuppressed recipients, and autogenic reimplants, were scanned using CT on days 3, 5, 7, 10, 14, 22 up to 134 days after operation. In addition to morphological analysis, bilateral densitometric CT measurements of the peripheral lung parenchyma were used to evaluate the intensity of interstitial infiltration of lung grafts. Altogether 67 postoperative CT studies were carried out. Simultaneous transbronchial/thoracic biopsies were undertaken. The mean follow-up time was 28 days (range 0-134 days). The experience obtained was then used in relation to SLT in a male patient for chronic obstructive pulmonary disease. All piglets had a typical hilar reimplantation response, which disappeared in 10-20 days. Two distinct patterns of radiological acute rejection were found. Increasing peripheral alveolar infiltrates reflected early massive rejection in untreated animals. In immunosuppressed animals, after the initial reimplantation response, acute rejection was detected as densitometrically measured diffuse interstitial infiltration over the whole graft. Local findings, like focal infections, were seen later in the lingula and basal portions of the graft. In the SLT patient, density changes preceded clinical rejection episodes, which responded to steroid therapy. In the experimental study, the lung graft was compared to normal contralateral lung. In the SLT patient, however, this was not possible, and, therefore, the subsequent repeated CT studies formed the basis of clinical follow-up. Sequential imaging and densitometric measurements allowed objective estimation of diffuse interstitial infiltration relating to rejection.