Abstract

Oedema, which can not be explained by a cardiovascular, renal, or any other systemic disease is a common complication of chronic obstructive pulmonary disease (COPD) and it is a poor prognostic sign. These patients are usually hypercapnic and in chronic respiratory failure and their renal blood flow is reduced but increases when the clinical status improves. Renal functional reserve (RFR) is an index of the capacity of the kidney to increase its function, by vasodilatation of glomerular arterioles and recruitment of dormant nephrons in response to stimuli such as oral protein load, amino acid and dopamine infusion. Doppler ultrasonography indices like renal artery pulsatility index (PI) and/or renal artery resistivity index (RI) can be used to calculate RFR in a noninvasive way. Twenty-one moderate or severe COPD patients (without any known renal disease) and 13 healthy controls were enrolled to study if there was any change in the RFR of the COPD patients when compared with the controls. The baseline PI and RI values were not different statistically in both groups and RFR was calculated by comparing the PI and RI values at baseline to 75th minute where the most prominent change was observed after oral protein load. It was found that RFR of the COPD patients was significantly lower than the controls by both PI and RI values (p<0.01 and p<0.01, respectively). These results suggest that decreased RFR may be useful to detect an early stage of impaired renal functions in COPD patients.