Abnormalities of pulmonary diffusion capacity in long-term survivors after kidney transplantation

Alterations in pulmonary function and interstitial changes in the lungs of renal transplant recipients have been described, but prospective longitudinal data are lacking.

A prospective analysis of pulmonary function tests and pulmonary CT in renal transplant recipients in stable condition at two different time points following kidney transplantation (KT).

Seventy-nine renal transplant recipients in stable condition were included. The first studies were performed 83 months (median) following KT. In 36 of these patients, it was possible to obtain a second set of studies after an additional follow-up period of 22 months.

Approximately 11% of all patients showed significant restrictive and obstructive abnormalities in pulmonary function tests. In the majority of transplant recipients, considerable defects in pulmonary diffusion capacity were documented: lung transfer factor for carbon monoxide, or transfer coefficient for carbon monoxide were < 80% of the predicted value in 57% and 76%, respectively. In 24% of the CT studies, substantial interstitial alterations were found. However, no significant correlations could be established between CT morphology and the presence of diffusion abnormalities. At the time of the second follow-up investigation, we found a further decrease in diffusion capacity in approximately 30% of patients despite an unchanged CT morphology in most of these patients.

We conclude that an impairment of pulmonary diffusion capacity exists in the majority of long-term survivors after KT. In our opinion, CT-detectable interstitial findings do not represent a causative factor for these abnormalities. A plausible hypothesis is a "low-grade pulmonary microvascular injury" in combination with a long-term decrease in pulmonary perfusion. The impact of these diffusion defects on symptomatology and prognosis in kidney transplant recipients is largely unclear, and further studies are needed.