Renal hemodynamics and renoprotection.

BACKGROUND

Angiotensin II (AII) is the well-known determinant of kidney damage increasing intraglomerular pressure, matrix expansion and fibroblast proliferation. Renin-angiotensin system (RAS) inhibition, limiting the hemodynamic effects of AII, reduces proteinuria and is renoprotective in the long term.

METHODS

We studied 15 chronic proteinuric patients by Doppler ultrasonography to clarify the intrarenal hemodynamic changes during RAS blockade by Benazepril (10-20 mg/day) alone and combined with Valsartan (80-160 mg/day). We also investigated the correlation between hemodynamic indices, RAS components and antiproteinuric effect.

RESULTS

After 1 month of Benazepril proteinuria, resistive index (RI) and pulsatility index (PI) significantly decreased and proteinuria reduction was directly correlated to decrease in RI (r = 0.55, p = 0.03). Contrarily, after 1 month of combined therapy, RI and PI restored to baseline and progressively increased in the following 3 months, while proteinuria decreased. Increase in RI was directly correlated to concomitant increase in plasma renin activity (r = 0.65, p = 0.01) suggesting a direct role of renin in restoring intrarenal resistances.

CONCLUSION

The hemodynamic changes caused by RAS inhibitors partially contribute to the antiproteinuric effect. Other RAS components, such as renin, may contribute to renal vasoconstriction and could be a further determinant of kidney damage besides a promising target for renoprotection.