MEASUREMENT OF RENAL-VEIN BLOOD-FLOW IN RATS BY HIGH-FIELD MAGNETIC-RESONANCE

The aim of the present study was to examine whether magnetic resonance imaging (MRI) based method for non-invasive in vivo measurement of ve in blood how in rats could be used to estimate renal blood flow (RBF). Measurements were performed using a high-field (7 Tesla) MRI scanner with a short echo time phase contrast velocity measurement pulse seque nce. The method was evaluated in vitro by flow measurements in an acry lic pipe and in vivo by recording left renal vein blood flow in normal and unilaterally nephrectomized rats. In a subset of animals RBF was measured by a direct method using C-14-tetraethylammoniumbromide. In v itro a high accuracy was found between applied and MRI measured flow r ates in the range from 0.5 to 33 ml/min (r = 0.997; P < 0.001). In viv o the MRI measured left renal vein blood flow was 70% higher in unilat erally nephrectomized animals compared to control animals (3.4 +/- 0.4 ml/min/ 100 g body wt vs. 2.0 +/- 0.1 ml/min/100 g body wt, P < 0.001 ). Direct measurements of RBF revealed comparable values (3.4 +/- 0.3 ml/min/100 g body wt vs. 2.3 +/- 0.4 ml/min/100 g body wt, P = 0.05). In addition, the left kidney volume was recorded by MRI with an increa se amounting to 40% (1.18 +/- 0.05 ml vs. 0.84 +/- 0.02 ml; P < 0.001) in the nephrectomized group compared to controls. Finally, a positive correlation was seen between left renal vein blood flow and MRI measu red renal volume (r = 0.91; P < 0.001). In summary, MRI is a non-invas ive tool by which measurement of renal vein blood flow can be performe d, and it is concluded that MRI-based renal vein how measurements can be used to estimate RBF in small rodents.