Significance of posture and workload in exercise renography

Exercise-induced alteration in renal function has been described in patients with essential hypertension. The aim of our study was to assess the significance of adopting a supine posture and the degree of workload required to induce these changes in patients with essential hypertension. The second aim was to assess whether the severity of hypertension had any influence on the development of exercise related renal dysfunction.

Fifteen patients were studied (nine patients with mild and untreated hypertension and six patients with drug resistant hypertension). Exercise renography was carried out using a cycloergometer with the patient lying in supine posture and a target exercise rate of 20 bpm over baseline rate. Each patient was injected with 100 MBq of 99mTc-MAG3 and renography was carried out for 20 minutes. Renography was repeated in rest condition only when an abnormality was observed in exercise scans.

Exercise renography was normal in 12 patients, while in 3 patients minor abnormalities were observed during exercise related to a minimal degree of pelvic dilatation. These changes remained substantially unmodified at rest. In none of the 15 patients did we find positive studies (i.e. reversible exercise induced prolongation of tracer transit caused by cortical retention). There was no difference in the results between patients with mild or severe hypertension.

Our results are different from previous reports on exercise renography since different groups have demonstrated exercise-induced renal dysfunction in the majority of patients with essential hypertension. The main differences between our protocol and that adopted in the literature relate to posture during exercise (upright vs. supine) and degree of workload (minor in supine exercise with less workload). These differences may have contributed to our results but further and larger studies are required to address the pathophysiological basis of exercise-induced alteration in renal function in association with essential hypertension.